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STAR-CCM+ - Science topic
Explore the latest questions and answers in STAR-CCM+, and find STAR-CCM+ experts.
Questions related to STAR-CCM+
I'm trying to do overset meshing in Planar Motion Mechanism (PMM) test in Star CCM+. while doing this I'm facing the issue that overset domain is moving outside from the overlap region. Thanks in advance.
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I guess Deniz is right. Seemingly your problem is generated by the way the interfaces were set. Please keep in mind that if you use a second order accurate numerical scheme, the size of the overlapping domain needs to be at least or four cells. This is crucially important for the communication between the component meshes.
I am doing solar still simulation by coupling of species and energy equation. I want to write source term for evaporation and condensation. For this mass of evaporation or condensation is required. but I am facing problem to write the field function of the expression m_c = [(-rho*Dm/Lg)* integral(dY/dy) dx ] with lower limit 0 and upper limt Lg(length of glass). Where rho = density, Dm = molecular diffusivity, Y = mass fraction of water vapor and y = vertical position.
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Also from the STAR-CCM+ Home Page: Much more than just a CFD solver, STAR-CCM+ is an entire engineering process for solving problems involving flow (of fluids or solids), heat transfer and stress.
Hi everyone, I am currently trying to simulate the RTM process (Resin Transfer Molding) with StarCCM+. The medium is a porous material and the flow is a mixture of air+resin (taken as Newtonian). I know how to do it with Fluent but I fail with Star CCM+. Has anyone succeeded in implenting both the porous and VOF models together in Star CCM+ ? Thank You for your feedback S. C.
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Hello Stéphane Champmartin, I am working on the simulation of drying a porous media (sand+binder) by hot air. I am using STARCCM + to represent the case. Can you please help me, if you have succeeded in implementing both the multiphase flow model and the porous media model in STARCCM+? Thanks in advance
in my star-ccm+ the geometric view is always initialized after importing the models, I have waited for 2 hours but without results. I think maybe my star-ccm+ is with some problems. Have someone ever met such problems? Could you help me? Thank you!
In the report window of STAR-CCM+, the input should be a part or region boundary. How could a portion of a part or region boundary be selected as input? Thank you
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Hi Mohammad . you should split it from the main body in the region section before starting your simulation, same as other boundaries like walls or inlet or outlet.
I want to analyse the impact of heat exchange mechanisms in a fluid contained in a box under different pressure levels using Star-CCM+. The Navier-Stokes solver fails when the pressure is low enough to produce KN>>1, under free molecular flow regime. I think this can be achieved by defining the physics continuum by selecting a User Defined EOS. I just wanted to know if this has been attempted or maybe a different method is better.
Hi I am simulating phase change material in star - ccm. I am unable to define physics condition for PCM material. I have rectangular box with white petroleum gelly. It will absorb solar radiation through PV panel. solid will change to liquid . How to define physics in star-ccm?
Hello, I am currently trying to solve a problem using Star-CCM+ that involves gas exiting a nozzle at high velocity and hitting the ground. The aim is to find the temp/pressure values on the point where the gas hits the ground (stagnation point). The Mach number at nozzle exit is 5. However, beyond Mach 3, the solver runs into convergence issues due to temperature anomalies (temperature exceeds the maximum allowable value which was set at 5000K). I am using steady, coupled flow, coupled energy, k-omega-SST models for the solution. Should I try setting the max allowable temperature in Star-CCM+ to higher than 5000K? Also, if there is any analytical way to scale the results I got for Mach 3 to Mach 5 (even if it is a rough estimate), that would be of great help to me.
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Thank you all for your suggestions!
How to do the translation give a initial displacement for floating free decay in morphing mesh in the star ccm？ But did someone can tell me how to do this manipulate？ It is not the overset mesh ，it is the morphing mesh。The free decay problem for a floating structure coupling a mooring line.
Hello everyone, hope all is good. I want to analyse multi-phase fluid flow through pipe, which software is best to do so ?
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Go for Ansys CFX or COMSOL.
I need thermophysical and electrical oil properties to investigation of DC discharge in oil. Are multicomponent mixture models effective and precise in such calculations? If yes, what MC-modells can You suggest? Can somebody advice something? Thank you a lot in advance!
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I suppose you are talking about normal octadecane (n-C18H38). You may try several engineering models for a reasonable temperature range up to about 600 K to 700 K. Although there are no extensive data measurements for this fluid. The one-parameter friction theory model: https://doi.org/10.1016/S0378-3812(00)00474-X, combined with the Peng and Robinson EoS can give you some reasonable pvT, viscosity, and phase behavior estimations. This approach can also be extended to thermal conductivity. But for most of the temperature range you are looking at, the octadecane will certainly be degraded. I even doubt you will have any CH4 left at all, as it starts decomposing at about 1000 K. So, you need to first figure out what compounds you will have left. But, at such temperatures, you are likely only to have some light gases and C. For the fluid phase, a simple model that may be useful to consider would be the one by Chung et al.: I would start here.
I'm using COMSOL for circuit breaker PSS-1 2D time-dependent simulation. I have coupled all moduls: Heat Transfer in Fluids, CFD-Modul, Electric Currents, Magnetic Fields, Moving Mesh in HT-Modul I use 3 HeatSources for Simulation of radiation, Joule-Heat(ec volumetric los), enthalpy transport. in CFD Modul I use Force for Lorenz-Force consideration EC and MF moduls are coupled with external current density. MF:full field, "in plane" field, gauge A-fixing boundary conditions: walls initial values: T=293K, P=1atm(with hydrostatic correction), DC terminal 100A and ground. between electrodes T=10000K or I tryed to use Gauss-Pulse function (quasi same effect) Solver: fully coupled Method: High-nonlinear Newton Goal: to simulate plasma in switching device correct and watch internal thermo-hydrodynamics and V-A characteristics of circuit breaker. when I start to calculate my modell, I receive no convergence in both Stationary and Time-Dependent cases. when somebody need a comsol-file, just ask it
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Agreed with the link provided by dear Ijaz Durrani
I have this problem when i take geometry in fluent .Model Information is incompatible with incoming mesh. How to resolve it?
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Right click 'Setup' and press reset. This will force you to start everything after the updated mesh from scratch. Don't bother looking for the error.
Hi I am trying to find some information as how to link up OpenFoam and Star CCM, however I am not able to find adequate information. Below is the details of the project. 1- Objective: to anticipate CFD results using machine learning, without doing actual simulation 2- Methodology: Collect Big data by using openfoam to run many iterations of different building geometries 3- Software used: OpenFoam, version 5, 1906 4- Solve time: 8 ~ 16 depending on model The main aim is to migrate the project from openFoam to STAR-CCM how can we convert the Mesh & Results data to a file format readable by STAR-CCM? Any suitable read up material on this
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Thanks for all your answers
Hi everyone, I'm right now trying to simulate a double piped heat exchanger in star ccm+. I've got everything set up and ran a few times. However, it has been giving me weird results. I think I got boundary conditions on interfaces wrong. Can someone help me with this? For this DPHE, there are 4 interfaces which are water/inner tube inside surface, air/ inner tube outside surface, air/turbulator, tubulator/inner tube outside surface and air/outer tube inside surface. For fluid/solid interfaces I set the thermal condition to be convection and used fluid temperature as ambient temp. For solid/solid interface which is the turbulator/inner tube outside surface, I set it to be adiabatic but I know this is wrong because there should be conduction between turbulator and the tube. So How do I set conduction for this interface? Also, the fluid temperature is going to change during the simulation, which means the ambient temperature is changing for all convection interfaces. Is the ambient I set for convection giong to change itself during the simulation? Much appreciated for any help.
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Hi do you mean the dynamic and kinetic conditions? For free surface you don't need to define this in StarCCM
Hello, I want to inject some particle clumps with diameter set as 2m into a cylinder. The width and height of the cylinder are both 7m. I set the mass flow rate as 50,000 kg/s. Since the particle mass is 1216.3kg, the particle flow rate should be about 40/s, at solution time 0.26s, 10 particles should have been injected but it did only injected 4. I wonder what could limit the particle flow rate and how I can inject more particles. Thank you!
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Hi in the injector setup, you can define "mass flow rate".
Hello, I want to simulate evaporation and condensation with STAR-CCM+ and I do not get it to work. I want to simulate the evaporation of a small amount of water in a pot (80°C) and simultaneously the condensation at the top cover (20°C). If I only use moist air (VOF), the condensation works fine. If I add a small amount of water (VOF), which has to evaporate first, the simulation diverges immediately. If the area is completely filled with water, no error occurs. A finer mesh or smaller time-step had no effect. How can i get this simulation to work properly? Thanks in advance
I'm rookie on STAR CCM+, I'm learning with YouTube tutorials, but I don't know how to analyze my results. I'd like to know how can I find the "coefficient drag" and "coefficient lift" on STAR CCM+. I'd be very grateful for your answer.
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I want know where can I find the drag and lift force on CFD. Can you tell me?
I'm doing a 2D simulation of a hypersonic shock in an aerodynamic tunnel and it has been hard to converge to the level points that i wanted to. i want to reduce skewness in general of the mesh (and especially in the vertex that's giving really high values). the problem is that im struggling to change this, right now im just avoiding different mesh sizes close to each other . are there any controllers in Star CCM+ to do this?
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Use the correct element type and mesh generation
i want to know how to generate a good/fine mesh, because there are several factors involve in this process like base size, prism layer(wall bounded flows) maximum cell size, surface growth etc. Will you please share your opinion, which factor be more important to generate good/fine mesh for problem.
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All factors are important. By studying them in a simple example like "flow over a flat-plate" the effect of each parameter could be visible. At each simulation change one of the above parameters and then track the changes of solution in the domain.
While working on tools like STAR CCM+, why AHMED body is considered to be the basic of 3D CAD modelling & what are it's applications in the real life industry??
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It is a generic car-type bluff body with a slant back has various angles from 0 – 40 degree. It is used as a benchmark test case for simulating the external aerodynamic flow characteristics over a car model
Hello all, I set up a case of DEM model in STAR CCM+ and I injected bricks made by particle clumps from the top. I wanted to mark out the cells which contained the particles injected , so I monitored the volume fraction of particles. However, I found that the value of volume fraction of particle clumps could be negative. What's more, when I tried to inject single sphere or polyhedral particles, the value of volume fraction could exceed 1. I am puzzled why this phenomenon could happen.
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In case of immiscible liquids, the size of the immiscible region can be influenced by pressure as the system would shift to the state of lower volume upon pressure increase. In case of negative excess volumes, applying sufficient pressure often leads to complete miscibility. This can be a great advantage e.g. in case of chemical reactions, where the reaction rate is limited by the transport through the phase boundary.
I am writing to inquire if there is a way to create a time-varying temperature field and apply it to a part on ABAQUS. I am trying to model a cylindrical tank using the coupled temperature-displacement approach for thermomechanical stress analysis during the heating/cooling cycle (i.e., thermal ratcheting). The model, solely composed of tank shell, will be heated up using a time-varying temp. field on the part's surface. To this end I prepared the Spatial temp. data (X, Y, Z, Field value) at each time step "t". But I am having trouble implementing this data on the ABAQUS platform. Could you advise on this matter? FYI, the temperature data was calculated using the STAR-CCM program. In this regard, will my issue require the STAR-CCM-ABAQUS co-simulation process? I ask because I hope my issue is solvable just on ABAQUS with simple manipulations.
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I replicate the manual: Defining time-dependent fields Abaqus/CAE Usage:In Abaqus/CAE only predefined temperature fields are available. Load module: Create Predefined Field: Step: analysis_step: choose Other for the Category and Temperature for the Types for Selected Step: select region: Distribution: Direct specification or select an analytical field or a DISCRETE FIELD, Amplitude: amplitude_name. Please note that DISCRETE FIELD (Distribution: (A) AnalyticalField; f(x): Type: Mapped field) can be inserted manually as tabular data (X,Y,Z,Temp) or read from file using context menu.
Hi I'm currently using snappyhex mesh for meshing my fluid domain to run simulation in openfoam. I found salome is better free alternative to snappyhexmesh, but the time required by the mesh created via salome is more than then mesh created using helyx (snappyhex). There is a module callled meshgems in salome to be purchased in order to create hex mesh. Is it worth buying meshgems to create hex mesh for openfoam application?
Steady flow in a chamber is easy to be achieved with pressure setting on inlet and outlet in either Fluent or Star-ccm+. While in OpenFOAM, it diverges or gives nonsense result if the flow was set only by pressure BCs, we are forced to set a velocity BC at inlet for most of the cases. Can anyone explain the reason in a mathematical way? Any idea is much appreciated!
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OpenFOAM is FVM. Like FDM and FEM, FVM has its strengths and weaknesses. Some of these arise from where the nodes are positioned on the elements and how the equations are linked from one node and cell to the surrounding ones. No method is perfect for all cases. One of the problems you get into with a staggered grid FDM or the FVM used in OpenFOAM is the pressure ambiguity you're describing. This ultimately gets back to the difference in order between the continuity equation and the momentum equations (Navier-Stokes). You can get this Ebook for free on 12/16, 12/24, 1/1, or 1/9 https://www.amazon.com/dp/B082FPFN1M (see second half of Chapter 3)
I would like to to run ship motion analyses in regular waves and as you guess, deforming mesh option is not working for periodic motions. So, if anyone exists here who is familiar to this kind of simulations, please share it how. Thank you.
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I am also trying to use the overset mesh to simulate the heaving motion. Can you share the tutorial of overset mesh? Thank you in advance. dibyarajadhikari@gmail.com
I am doing a wave modelling where there are 2 bodies undergoing multimotions. I want to apply damping in between the 2 bodies. Is there any way to do that?
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Hi You can use damping coefficient k2 in contact properties of body coupling. See the attached file. Regards
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Hello, I am pretty new with this CFD topic. I already read plenty articles and checked tutorials regarding this topic. I am about to design an underwater towed body (close to the surface, a part is surface piercing) and I want to get informations regarding the resistance of the hull. For this I was looking for comparable models. The best I found was a Torpedo with an wetted surface very close to my body. I set up a simulation and now I have results, but I am not really sure, if everything I set up was right. So I set up a simulation for the Torpedo as well (same settings), but the average Drag is twice as much as reported in the paper. To specify my questions: 1. There are plenty peaks within the Drag curve shouldn´t (if all goes right) the curves become "flat"? 2. I am not sure about the boundary settings, orientated at the boat tutorial. I added some pictures. If you need more information, just let me know. Thanks for your help
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Hi Jan, To start with, no, your simulation doesn't seem to have converged - those peaks look rather suspicious. If there is a steady solution for your simulation, the drag should indeed converge to a constant value. Those peaks look like some numerical artefact, but still, taking a closer look at your results (velocity field, pressure, volume fraction, etc.) as a function of time might be helpful. What settings to choose depends on your problem: Froude number, Reynolds number, whether to expect cavitation, streaking, etc. Sorry, I couldn't make much of the screenshots you included. Are you using a steady or an unsteady solver? RANS, LES, DNS, laminar? Domain size relative to towed body size? Symmetry? Rigid body motion/moving mesh? You mentioned a paper that reported drag values for this torpedo. I think the best way to go would be to try and reproduce these results first, perhaps contact the authors to find out which settings they used. Hope this helps, Sita
Hi, I want to apply a temperature dependent heat flux (B.C) in a transient heat tranfer analysis. The problem concerns the need to change the boundary condition during the analysis because the heat flux should be calculated by the changing temperature of the system over the time. Is there a method I can apply in Ansys Fluent or in an other CFD software like COMSOL or Star ccm+ ? In particular, the heat flux should have the following law: q(Tw,t) = md[cd(Tsat - Td) + hfg + cp,v(Tw(t) - Tsat)] The only variable in the expression is Tw [K], that is space and time dependent. The output I desire is the final temperature field. Thank you.
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You can do this very easy in Workbench by defining Derived parameters. First of all, you need to select the temperature as a parameter in fluent. After doing this, you will be able to see this parameter in Workbench. Double click the "Parameter Set". In the "New name" section, type the name of the derived parameter (which going to be heat flux in your case). in the bottom properties table, define the expression the way you want (The equation you are interested). Be aware that you need to define the unit at the end of the expression (See attached picture). This way the moment you change the boundary condition, the heat flux will change and you can easily form a design table and solve all the scenarios that you want. Off course you can use scripting to solve all the scenarios as well.
I recently updated my OpenFOAM version 4.0 to 6. I'm facing an issue in the direction of flow. My flow is always pointing in x direction. Hence I tried to change the flow axis in a tutorial windaroundbuildings in simplefoam. The default wind direction was 'x' axis, so there was no issues. When I changed the Uinlet to (0 10 0) I mean the flow is in y direction, still the flow is pointing in x direction. I'm concerned about this flow direction because in my real case, I need the flow to be in 'y' axis but the flow is along 'x' axis. Is this a bug in openfoam 6? (I have attached the image of the tutorials in which I changed the flow axis to be 'y' but still in paraview glyph is along 'x' axis) Also I tried to run an interfoam solver, initially I set the writeinterval to be 0.5 then I thought of reducing it to 0.1, when the time was around 0.2 seconds to see what happens at 0.3 seconds, instead the program terminated with error 0.1 has already completed. Is it also bug where we can't adjust or reduce the writeinterval in OpenFOAM 6?
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I apologise Hi when I looked into the velocity profile, I think no issues with the change in direction. I think I made error in looking into the vector or glyph. but still I'm not sure why the simulation terminates if the write interval is reduced.
I am able to find the drag coefficient (CD) using Report > Force Coefficient. However I am unsure how to find the inertia coefficient. Is there way STAR can produce the value directly?
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Easier way to define the calculation than macro is definition through user defined Field function (Tools -> Field functions).
Hello All, I'm new to porous media simulations. I'm trying to create a pressure drop using porous media. I plotted the velocity vs dP/L and curved fitted using the equation Ax^2+Bx. I used A as inertial resistance and B as viscous resistance. My viscous resistance value is one order of magnitude less than the inertial resistance. Kindly let me know if this trend is acceptable, I heard from some that the viscous resistance should always be higher than the inertial resistance. I can provide more info if needed. Thank you.
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Dear Bharath Ram Ravi, The ratio of inertial to viscous resistance in a porous media depends for a STEADY flow (constant pressure difference imposed across the medium) on the Reynolds number Re defined as: Re=U d/nu. U is a characteristic flow velocity (filter velocity), d is a typical pore diameter and nu is the kinematic viscosity (dynamic viscosity divided by density) of the fluid. For an imposed harmonic unsteady pressure difference with frequency f one should consider the ratio of unsteady inertial force and viscous forces ( 2 pi f U)/(nu U/d^2)=(2 pi f d^2)/nu, where pi=3.14... Hence the answer depends on the characteristic flow conditions you are considering. These are best described in terms of dimensionless numbers. Regards, Mico
Software to show simulation has to be STAR CCM+ bore diameter of pipe is around 10-20 cm
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What aspect required a UDF in STAR-CCM+? Euler-Lagrangian coupling has a come standard for many years!
Hi everyone, I'm runing a simulation in star-ccm+ for a double pipe heat exchanger. There is 75C water in the inner tube and 27C air through the outer shell. There are also few vortex generators in the annulus region. When I ran the simulation, temperature on the vortex generators raise to 4000C and I'm not sure what cuased it. Can someone help me figure out what the problem could be to cause this abnormal temperature rise? Thanks a lot
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Hi Yihan, This issue is commonly find, when the following points are not considered: - The thermal conductivity of the fluid is given in kW/mK, and Star CCM+ specify this property in W/mK. - The interfaces or contact in both region are not well described. - There is a issue on the boundary condition. However, check the thermal conductivity of the fluid, your issue could be fixed by changing this value to the correct one.
I am doing a CFD study on a baseball falling into a water tank. I am using overset mesh but I am not sure what physics model to use to simulate the water tank. I am also confused about what boundary condition to use on the water tank. I tried to use VOF waves but I don't know if that's the right model. And also how should I setup my 6-DOF values so that the baseball is a freefall object?
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Remember that a sphere sheds a helical vortex and at the relatively slow speeds of a baseball in water, this may produce some funky results. Granted the lacings will help some compared to a smooth sphere of the same size and density, but I doubt either will fall straight. I know a 100 pound led ball we dropped in a 100 ft deep tank in the 1980's kited off more than 30 feet in a non straight- pseudo helical direction over that limited fall range.
Hi, I'm trying to simulate the flow underneath a ship with a moonpool to look at the accumulation of water inside the moonpool with the use of passive scalar in Star-CCM+. Is there a way to calculate the passive scalar going in and out of the domain? I have tried using a user defined field function for both the inlet and outlet(abs(${Passive ScalarBoundaryFlux}*mag($$Area))), and then found the percentage of each passive scalar by divining flow rates((outlet/inlet)*100) without any luck. Do anyone have and idea how to do this? Attached is a picture of my domain where the inlet is at the bottom front of the tank and the bottom. The outlet is at the bottom back end of the tank.
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Your model is not going to be very useful without considering the baffles and their damping. There are a lot of studies of flow in and out of a moon pool in the open literature. In general this is a very difficult problem. If the moon pool has doors, then they offer some damping at the opening. If there are slotted baffles or perforated baffles or changes in cross section those are all important to the actual motions. The pressure in the space above the moon pool is also a critical concern. If it's open to the sky, there's no problem. If it's and enclosed space, the oscillating pressure can be very dangerous to people working in there. In general moon pools that open into enclosed spaces need large vents to the weather deck to keep the pressure from damaging people eardrums, making them sick and in extreme cases causing "the bends." Remember that you need well rounded structural corners to remove bending stress concentrations on the hull girder and to meet IACS rules. Good Luck.
I am conducting transient state simulations on wave forces on a vertical cylinder in Star CCM, while trying validate my results using ANSYS AQWA. I was wondering if anyone knew any differences and similarities between the two softwares? Thanks in advance
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Can you using the ANSYS AQWA. It is the best for your problem.
I am modeling a double pipe heat exchanger in Star-CCM+ and I have some issues with meshing. Since there are two pipes I created two regions for the model and I tried to mesh each region with its own mesh setup. However, Star-CCM+ doesn't let me assign a mesh to certain region. It automatically selected both regions. I'm wondering if this is possible to assign different meshes to different regions. If it is can someone helpe me with this? Much appreciated if someone can help.
Hi! I am working on the design of liquid cooling BTMS for a electric racing car. When I simulate the thermal behavior of the cooling plate.The streamline always show half of what it should be.It confused me a lot. So,what is the problem with the streamline?
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Just need to change the maximum propagation of the streamline.
I am doing a simulation of a forced air cooling of the battery pack with an inlet temperature of 30 °C. When I changed the intake air volume of the forced cooling fan from 30 CFM to 120 CFM in STARCCM+, in the simulation of 120 CFM, the temperature suddenly jumped from 30°C to 48°C, but quickly fell back to 34°C. This is caused by the unreasonable setting of boundary conditions, or whether the increase in the amount of intake air does cause a sudden increase in temperature rise？
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Try to achieve less than 0.8 of skewness in your mesh, it should help for the convergence of the energy. You can also create an inflation in the surfaces in contact with the air to improve the mesh in the boundary layer. Use the standart k-epsilon model for the energy to be sure if the air is in turbulent or laminar flow.
The relaxation factor can speed up the calculation. In a passive air cooling simulation of the battery pack, I used the default parameter value (0.99) afforded by STAR-CCM+, but the temperature of battery pack is always rising and cannot be stabilized. But when I changed the parameter to 0.5, the temperature curve became stable. As shown in Figure 1 and Figure 2, the relaxation factor is changed in 970s, the oscillation of the residual is also reduced. The temperature is also balanced. According to the experience of your research, what range of relaxation factor can make the simulation get better results? Thank you!
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If the simulation converges, the relaxation factor should not affect the solution. As you say, it can affect how fast convergence happens. However, too high relaxation factors may destabilize the simulation, which will lead to wrong results. So "the relaxation factor does not affect results" only counts when the relaxation factor is low enough to lead to a converged solution.
Hello, i'am trying to run a simulation to obtain the drag of a boat running on the surface of water. I set up the simulation as fine as I know. Concerning this kind of simulation, the prism layer is very important since they allows me to evaluate aspects like pressure, which is the main component of the drag of a boat. I read how the Boundaries Layer is analyse in star ccm, so I know the interval's value of Y+ and the different treatment that star ccm+ use. The difficulty for me is to settle the value that I want for y+ What I read, is that we do not know the value before running the simulation... we know at the end of it. okay... and from here it seems to me that we "play" with the options like strechct factor, number of prims layer to obtain the goal value. I also read the "good" practice to have the value that we want. Let's said, I use the good practice for it... since it is just a supposition i may not have can the value that i want at the end... Problem is I'am running simulations (evaluating the drag of boat) which take 6 to 8hrs to converge... so I guess that there is another way to evaluate the values of y+ before running the entire simulation... I have look the help.. but I didn't find it yet. Can you please help me solve this problem?
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Hello, have your resolved your problem? I am sorry to reply you so late, as my work was too busy in the last week. Unfortunately, I cannot open your sim.file because of my older version of STAR-CCM+ (10.04.008). Can you give me the ship geometry in IGES or CCM? So I can import it in my version to do some test.
I am trying to simulate a VOF 5th-Order wave in Star-CCM+. The wave shall be 4.2 m long and 0.094 m high. For this I use a domain which is 5 wave lengths long. The two last wave lengths are used for damping. Despite the dampening zone, there is an overlapping wave, which is getting smaller and smaller starting from the outlet. This wave is visible in the Line Integral Convolution of the velocity (see VelocityZoom.png ) and through the deformation of the water surface in the area of the overlapping (see Wave Cut Profile.png). Is this normal or can i do something better about my damping? I already tried a longer damping zone (3 wave lengths) and a porous region but it showed the similar effect of reflection.
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Check the grid resolution of your simulation. I think the amount of cells are not enough. Use the 2D mesh instead of the 3D one.
If we have to choose between both the cfd packages for convection and radiation simulation, which one will be better?
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I agree that is quite difficult to give a definite answer. Formally, at the same accuracy order, on the same grid, at the same numerical precision any consistent and stable method should converge to the same solution. That can be observed in specific simple test-cases. In the real word of CFD there are so many additional issues that one should focus the comparison between codes only for a specific flow problem to have some useful assessment. Some years ago we did something about such comparison of codes for a specific problem.
Which cell size has to be selected for calculation of courant number? If I consider the smallest cell height in my hexahedral mesh for achieving courant number 0.8, I end up having my time step of size 1.2668e-5 which is extremely small. Is it a correct approach to use base size instead of smallest cell size?
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The Courant number is by definition a local variable therefore, depending on the velocity field and mesh size, you have a field of the cfl variable. The numerical stability constraint must be based on the most critical value. Do not forget that in presence of explicit scheme for both advection and diffusion, you have to consider also the diffusive constraint.
I am doing air-water VOF simulation with pressure and velocity fields initialized from well converged single phase solution. After few iterations star-ccm throws a message in output window saying "breaking out of time step. Time solution is in an inconsistent state". But it comes out of the time-step only after finishing all inner iterations. Why does it occur and what is the importance of this warning? Is there a way to handle this? Thank you
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I do not know Star CCM+ very well. But if you initialize velocity and pressure fields from a single phase flow calculation for a VOF simulation of at least two fluids of different density, than your pressure field is at least inconsistent with respect to the hydrodynamic pressure in your fluid(s). In dependence on how your configuration looks like, this can cause divergence right away... I could imagine, that CCM+ might claim about this. But not sure. Regards, Th. Frank.
Hi everyone... I have been trying to simulate ship movement in Head Waves in Star CCM+ v8.06 using overset mesh. In order to capture the wave height correctly, around 40 cells have to be provided and when I initialize, overset mesh shows error..!! So I removed volumetric refinement and then tried, It initialized..!! What I understand is that if the refinement goes less than maximum cell size in the overset mesh (Global Value) it is not getting initialized... But I can not avoid the volumetric refinement since it is essential for wave simulation. Anyone experienced same issue..? Someone can tell me how to resolve this issue..?
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Hi Dear Hariharan. It is very important that height of the refinement should be refined as well as other directions and have some space for the free-surface. It is recommended to not use Over-set mesh, DFBI models could help you. Check the motion specs in the tools node.
Hello, Im trying to simulate a U-shaped thermosyphon with an outer copper casing. In short I have done the following. 1. Three part geometry, of outer copper tube, inner water and air. The inner geometry is divided into two since I want to initialise both regions differently, with air and water. 2. Used the Eulerian multiphase VOF model with multi-component liquid - water as phase 1. Phase 2 was a multi-component gas with air and water vapor. 3. I enable the evaporation/condensation model and link h20 water with that of vapor. 4. I initialise the air region of the geometry with 1.0 mass fraction of air and 0.0 of the others and similarly for the water region. However I get the error that sum of mass fractions is zero. I dont know why this is happening. If I put random non-zero values, the simulation runs but crashes immediately with AMG solver non-convergence. Any tips ? Thank you.
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I have not experience in heat transfer and phase change simulation, but I think this link can be helpful. If you upload error I maybe can help. Best Regards
Hello Guys, i have a little experience in star ccm+ modelisation. So now i have to modelize Panning hull in star ccm, to determine the drag,pression and trim.... My problem is to design a good "mesh" so i can have results that can be good enough. Here, i saw a lot of publications about that, but i can't find none explicite about how to chose a suitable high of cells.... Another question is the type of cells: What is the best between the polyhedral and the trimmed mesh? (i often use the Trimmed mesh). Thank in advance for your answers.
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KCS model is in Tutorial Guide in motion you can see find that. for validate a prism layer you can validation with empirical results or Y+ range or VOF scheme. for total thickness, use the bondary layer formolation is better. Best Regards
Hi everyone, I am trying to simulate turning circle and zig-zag maneuvering tests for a mariner class vessel using Star CCM+ (hull, rudder, and propeller come into the picture) using a set of overset meshes. I have made a few attempts and not yet succeeded. I would like to know if anyone in the community has done it or attempted it. If yes, kindly give me some suggestions. Thank you. Following links will be helpful.
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For simulate this, if surge ignored, you can use morphing mesh But it is very slow. for Zig Zag motion you need to define 2 DFBI, one for body and one for rudders, and then in angular velocity for rudders, you can define Sin field functions. attention if your surge velocity assigns to DFBI, in second DFBI you need also to define translation velocity as well as first DFBI. Best Regards
Hello Guys, i'am trying the simulate a boat advancing in head wave. I realise all the steps until where i have to indicate the wave lenght or the period of the wave. Usually i just indicate the wave lenght, but i want to know how Star ccm+ evaluate the lenght of wave when you indicate the period. I ask that beacause when i try with the data : T=5.5s and the depth d=100m, it give me the wave lenht of 227.8m; problem is , when i use the formula indicate in the tutorials, i mean the relation of dispersion, i never find the same result. What is the problem , since Star have indicated theorically how to calculate it.
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In addition you can see this article or star tutorial in VOF Waves Formulation subject.
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My transient simulation showed sudden divergence from iteration number 247880. Residuals reached to the scale of 1e+141 in next 500 iterations. I identified the problem and I want to fix it. Is there a way to delete/undo the solution of those last 500 iterations and apply the fix so that I can avoid re-running the solution from iteration 1 which would take almost 60hrs of computation time. Thank you in advance, PS: Solution history was not created
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It's not possible to go back to an arbitrary iteration. Otherwise StarCCM+ would need to save the data of all gridpoints for every iteration. This would create huge files. If you want to avoid such a problem I recommend the autosave feature. This lets you save your simulation every x-steps (lets say 100 for example) in a new file. That's the easiest solution to avoid such problems in the future.
Hi every body I saw in cfd book and cfd references " the cfl (Courant) number should below than 1' but in official star-ccm+ suggested bigger cfl for outer current to active HRIC scheme. whats your suggestions. Thanks in advance.
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To understand the role (numerical but also physical) of the CFL number, you can consider the 1D case CFL=u*Delta_t/h. Just rewrite u=dx/dt so that you can write CFL=(dx/dt)/(h/Delta_t). This way you see that the number is the rate between the exact slope of the characteristic line and the slope of the discrete approximation. When CFL<=1 you have that the information travels using only data contained in the step size h. This has relevance for the explicit methods for hyperbolic equations, the numerical stability depending on this parameter. Rarely implicit scheme are used for hyperbolic equations. Generally, in a 3D code the CFL number depends on the local values of the veloctiy components (or sound velocity for compressible flow), it is used to be less than 1 for accurate transient simulation and greater than 1 when the description of transient is not necessary. Automatic selection fo the time step is possible in Star CCM+ as you can see here
Hi Friends I am using star ccm. I need to draw helical pipe. Is it possible to draw helical structure in star ccm ? If yes , how?
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thanks for your guidance.
I have very limited knowledge about the STAR-CCM software. For my project I need to make a complex nozzle profile and simulate it in STAR-CCM. But I don't know how to do it. Please help me with some source regarding same.
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hi I suggest you to see star tutorial and star help. in star tutorial usually you can see examples for your subject. best regards
Hello Guys.. I'am trying to modelize a boat moving in the waves. (I mean the waves moving around the boat..) So, like i have seen in the tutorials i divide the boat in 2 symmetrical parts and then i mesh it,using the Overset mesh option. I run the simulation and then i got errors like "The recevor can't find cells from the donor" or vice versa... I know that the Overlap and the Overset parts have to have the same order of height cells..so i guess that the problem is not coming from that option. I tried to verify what's going wrong and i found that at the mid plan, my mesh got a bunch of holes like you can see in the pictures and i don't know why. I tried the simulate the entire boat, the simulation run fine and i didn't get anymore hole at that same plan, but you can guess it needs MORE time to get the results. So , can you please help with that?
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in star tutorials they mesh region node by node. star has direct mesh methods and can import mesh from other meshing programs. i think they aren't mesh in star and import mesh from other program or mesh node by node. if in simulation mesh use curvature control and surface control you can decrease number of cells and decrease time run. do refining free surface similar than KCS example. for increase accuracy use hyperbolic tangent prism layer mesh. then without reducing accuracy you can decrease mesh in far from body. other trick is use field function meshes. i still newcomer in this trick.
In Volume of fluid method which is the interface reconstruction scheme used in STAR CCM+? Where I can get the details of such schemes? Thanks in advance...
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star Certain the schemes under vof with CFL_l and CFL_u automatically.
I have to simulate flow of coolant through different channels having different cross sections such rectangular, circular to predict the heat transfer rate and pressure drop. I have to perform this using star ccm+. It is the first time I am using it and can't find any tutorials regarding heat transfer. Anyone with prior experience please help me out
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hi Hamit Can answer is major and nice. but i can add something: you can find some good advice's for this kind of problem in star tutorial. in report's nod ,commonly results function had listed but if your required result isn't there, you can define it in expression report. if you wanna result in certain nod or line or part or reign you must define it first. for that you can define it in geometry>>part or in derived part or in tools>>shapes. beast rigard
I am studying external aerodynamics on Ground vehicles. And I am using Star CCM+ for my simulation. To achieve better drag and lift results, I got to know that Y+ plays an important role. So how can I specify the first wall distance in Star CCM+? I tried to change the number of prism layers, prism layer stretching, Prism layer total thickness. But I didn't find any improvement.
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hi Rusheendra Nani in star ccm you needn't Calculate first Layer Height. because in star in scenes nod in scalars you can plot y+ . if you wanna y+ on some line you can define line in derived parts and then create report y+ on this line. if you wanna change first layer height gonna in meshes nod in prism layer nod change distribution mod to wall thickness. other guys give good advice's for y+ range. best regards
Hi I have used STAR-CCM+ version 12 for simulation displacement and deformation of the barge. I have defined motion as DFBI Morphing, and I have used directed mesh for define solid mesh. when I want to run my simulation I get the following warning. How can i solve it?
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What is the basic difference between Star ccm+, openFoam and ansys?
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Dear all, thanks for your recommendations. I have decided to use OpenFoam mostly and sometimes Star ccm+. I will update you all on my results.
Hi all, I am trying to model a thermosyphon (which is a heat transfer device based on evaporation and condensation processes) using Star-CCM+. The details were taken from this publication I have attached the mesh I have used and the screen shots of models in Star. The problem I am facing is, phase change does not happen even after 40 seconds of run. Anybody who has experience on this, please do comment. Thanks in advance.
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Using STAR CCM+ it is possible to set an asymptotic stopping criteria. Is it also possible to do this using ANSYS Fluent? If yes, then how? Thanks
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Yes, it is possible to set such criteria. You can do it following different ways: - Define your parameter using Solution/Monitors/Report File/New in the main tree. Then activate the corresponding convergence condition in Solving/Reports/Convergence. See Users' Guide for more details. - Define your parameter every iteration (time step) in a DEFINE_EXECUTE_AT_END UDF (User Defined Function), test its value and stop the simulation if convergence is satisfied. See Fluent Customization Manual for more details. Regards
I have tried to validate the acoustic pressure and unsteady RANS pressure in near field using FW-H equation in Star CCM+ for open water marine propeller . I have solved the FW-H equation both impermeable surface and permeable surface approach. However, two different approaches give different results in terms of acoustic pressure as expected. In addition, the acoustic pressure is higher than dynamic pressure in near field. Does anyone handle this problem? What is the meaning of the hydrodynamic pressure exactly to compare the acoustic pressure?
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Placement of permeable surface is very critical and it is recommended that it should be placed in the region of uniform flow/no flow. it ensures that permeable surface records mostly only acoustic pressure. But before applying this approach following points needs to be validated to ensure basic requirement of FWH approach. Mesh resolution should be sufficient enough to capture acoustic signals of highest frequency of interest. URANS is not appropriate as by definition/formulation it gives time avg. quantities which doesn't have acoustic component. Therefore one should use DES/LES to resolve acoustic pressure. Once above two points are taken care off then it comes resolving time domain. It should have sufficient resolution so that it captures acoustic signal with fair accuracy.
I need to design a simulation, where model is stationary and the mesh is moving. Please share any tutorials and ideas Thank you
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Hi Manigandan, The best tutorial for your work is Ansys fluent User guide. Regards
Hi, I am going to simulate a 2D aeroacoustics simulation in Fluent using a DES model on a stator. Actually, the simulation should be performed on a complete 3D rotor-stator setup but due to some limitations, I don't have access to the rotor geometry and computing power. A simplified model of my setup is shown in the attached picture. I have been searching for parameters that I can extract from the DES simulations. These are the following parameters that I can think of: 1)A common parameter is the FFT of pressure data recorded in the wake region of the blade. Using FFT, I want to see if I can see tonal noise peaks or broadband peaks. Based on these observations I can characterize the sound sources such as vortex shedding or just random turbulence. 2) Another parameter that I have come across is the sound pressure which can be calculated by subtracting the instantaneous pressure from the average pressure. How this can be done in Fluent, I am not sure. 3) The other is " divergence of velocity" or dilatation contours. I found it in this article I am not able to understand what's the significance of this parameter. 4) Another quantity that can be visualized is the normalized Q-criterion, but this will be good to see the turbulence sources and not aeroacoustics as such. 5) Also, I was wondering if one can actually extract the noise from a pressure signal at a point so that you can hear it. I came across this in the STAR-CCM+'s user guide some time ago and they say that it can be done. The guide mentioned that that one needs to perform inverse FFT of the signal. Perhaps, people with experience in aeroacoustics can suggest me any additional parameters that can be used. Although the near-field region sound is of interest and not far-field, I am open to using the FW-H model if it provides additional insights.
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Dear Ishan Nande, Here are my suggestions: 1) a 2d simulation of turbulence might be questioned by many people 2) If you extract the pressure signals from the wake this will not be purely noise, but noise+flow. To talk about pure acoustics you need to study it out of the flow, in the far-field. 3) a calculation of the Overall Sound Pressure Level (OASPL) is based on a value of the Root Mean Square (RMS) of pressure fluctuations p'rms [Pa] (referenced to the treshhold of human hearing 2*10^-5 Pa): OASPL dB = 10 log (p'rms^2/p'ref^2) dB. The Sound Pressure Level is a frequency dependent parameter. To get it you need to make a DFFT of p'(t) [Pa] first and transfer the result to the logarithmic scale and get power spectrum of the signal (exact formulas to do that you can get from Matlab examples). As a result you get SPL(f). If you integrate SPL(f) you should get OASPL dB (valuable check). 4) FW-H model is designed for MOVING (e.g. rotating) surfaces in open space... I hope it was usefull. Oskar S.
So I ran a simulation to generate waves in a flume. I need a very accurate detail of what is happening at the air-water interface. The results shows too many velocity vectors and stream lines at the interface since it is very finely meshed. Is it possible to keep the meshing as such and reduce no.of vectors shown in the solution ?
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in vector scene and increase geometric spacing: if you put 10, you want to draw 1 vector on 10 vectors in displayer vector, open glyph (+)
Dear All I want to Run my STAR-CD Model with Subroutine codes. But when I click on Run button, I face with this comment: (The Picture is attached) "PNP: ***ERROR*** Cannot find required tool "dumpbin" for dumping object file symbols. PNP: ==> This binary utility is normally installed with your C/Fortran compilers." Also I have Visual Studio 2012. Can anyone help me?
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Dumpbin is a tool that resides somewhere in the Visual Studio directories. You can search for it with c: cd \ dir dumpbin.exe /s Then you should set the appropriate environment variable of your tool (perhaps PATH) to the directory of dumpbin.exe A dirty hack would be to copy dumpbin.exe into the binary directory of your software. Dumpbin is used to inspect DLLs for function entry points. In DLLs, functions are renamed such that the name contains the types of the expected parameters. Regards, Joachim
Hi We are simulating injection of air bubble in flowing water (to reduce frictional resistance) by using STAR CCM. We are facing difficulties in formation of air bubble in simulation. It has 3D Geometry Does anyone know setting of formation of air bubble in water in STAR CCM?
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We need more information regarding your case, I guess. Despite the fact that the position of the bubble inlet (bulk flow or close to wall or bottom) is very important, I can imagine three general scenarios: 1) Low fluid velocity and large gas flow rate: large bubble cavity can be generated. My recommendation: VoF Model. 2) High fluid velocity and low gas flow rate: bubbles get immediately disrupted near the inlet and possibly break up further through shear forces. My recommendation: Lagrange Particle Tracking (maybe combined with a proper bubble break-up model). 3) High fluid velocity and high gas flow rate: bubbles can coalesce and breakup as well. My recommendation: Euler-Euler Model or Mixed VoF-Euler-Euler Model like in the Solver multiphaseEulerFoam in the OpenFOAM software Unfortunately, I never worked with Star-CCM+.
Hi, I'm a fresh graduate and have been asked to do some CFD validation for some of the ships. I've been running my simulation for about 3 days with a 12 Core Intel Computer (Lack of funds to get more processors) and my results have been fluctuating rather showing a smooth sine curve. I'm really new to CFD and I basically self taught myself but I'm having a hard time to interpret the residual to ensure that my simulation is converging or that I have doing it all wrong. Details of the simulation is as below; Model: All y+ Wall Treatment Mesh:Prism Layer Mesher Eulerian Multiphase Surface Remesher Exact Wall Distance Trimmer Gradients Gravity Implicit Unsteady K-Omega Turbulence Multiphase Equation of State Multiphase Interaction Multiphase Mixture RANS Segregated Flow 3D SST (Menter) K-Omega VOF Waves VOF No. cells =776154 Time step = 0.035s No. inner iteration = 20 I've attached my generated mesh, residual monitor, Total Resistance Residual. Any help is much appreciated. Daniel
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Mojtaba First, you should note that the Value of time step is very critical for obtaining a converged solution. The current value is too large. It is better to decrease it to 0.001 or even 0.0005. Furthermore, based on the provided resistant plot, it is clear that you should change the distribution over and around the hull surface. Generally, 700,000 cells are sufficient for such hull you have considered. However, you should redistribute the mesh in a way that hull surface, boundary layer and free surface are discretize, correctly. Based on my previous experience, I believe that you can obtain a converged solution, Only by changing the mesh distribution (not increasing the cells) and adjusting the time step. Best, Abbas
Hello all when I was simulating the foil alone(open water condition ) which undergoes both translation and rotation. I have noticed that the foil is slowly moving in the X direction(where x direction motion is restricted). Actually, I have confused why it is happening. At the start of the simulation both the lab and managed coordinates are at the same point. After iterating it seems there is slight change in the position of managed coordinates while the lab coordinate is at the same location. Thus it causes the foil to move out of the overlap region and causes an error. Here I am attaching the images. could anyone help me in figuring this problem? Thanks in advance.
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Dear Gianluca Thank you for your reply I will try with this and let you know.
I am simulating a two-phase flow nozzle of water and air with STAR CCM+ from cd-adapco. Validating against a dozen of experimental data, different grids provided agreement and disagreements in some case where none of the girds was found to be able of predicting all the cases at the same time accurately. So I was wondering is there any specific refinement or more importantly a type of grid of (structured /non-structured girds) are more suitable?
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Hello, I have decided to update this post by attaching my research and conclusion on the proper grid generation for VOF method. Thank you all for your helpful comments. Hope this post helps anyone facing similar problems.
I am working on a simulation of a square cavity which has different elements inside on star ccm+. I had problems for meshing the model due to self-intersections. I'm using an automated mesh to solve it but where the surfaces of the different parts are touching each other, it damages the geometry. I don't know how to solve this problem. If you have any idea.
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If possible please send the current picture of the mesh after motion and the various parameters which you have used.
Hi Everyone, For simulating particle distribution inside an office room I am using DPM model in ansys fluent. But DPM will only give particle trajectories not mass concentration. I learned that using PSI-C method we can get the particle mass concentration. I am using one way coupling for particle. Could anyone help me with this. Thanks
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Dear Mithresh, I attached one article describing how the PSI-C linked with DPM. Hope it helpful.
I recently finished an MSc project on cavitation over a 3d hydrofoil. While running a DES simulation for cavitation on NACA 0015 in Star-ccm+, I observed vapours near the outlet developing after the bubble diminished from the trailing edge. The pic attached shows the volume fraction of vapour at 100ms. The vapours downstream start developing at 90ms, would be great if you could shed some light as I am still an amateur, could this be flashing or cavitation inception in the vortices developed?. The conditions are at σ = 1, inlet velocity 6m/s and outlet pressure 20.9 kPa. Thank you.
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The structure close to the trailing edge could be physical, but the rest are spurious. Looks a bit like it could be in proximity to a mesh coarsening if you have a refinement wedge around the foil?
Anybody knows a model for double diffusion convection using star ccm+ ? or even with other software package. The only difference in double diffusion natural convection from normal natural convection is that of one additional concentration energy equation. Although I have codes but I wanna try it using a software package also.
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You can try FLUENT, which allows computation of natural convection by temperature and concentration driving force separately. I have done both. Good luck! KK
Hi, The turbulence model that i am using is Realizable K-epsilon. I know that for unsteady condition, the residuals should be below 10E-3. All my residuals look OK except for Tdr and Tke. Does it affect the convergence of the solution? If they are normalized, can i just ignore them? Thanks for the reply and help!
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You can ignore them, but if you want converge them with the residuals below 10E-3 run your program by initialize the latest results. Good luck.
Hello there, I am a fresher to Star CCM+. Right now I am working on drag investigation of ground vehicles. I am doing simulations which I learned from youtube tutorials. I am posting the procedure that I have done and the results. Please have a look and any suggestions will be greatly helpful. vehicle body - (Mini van) l*b*h= 4.9*2.2*2, Frontal area - 1.74 mt^2 (half body simulation) Wind tunnel- 10mts front to body, 30mts back to body, width 10mts, height 8mts Mesh- (1.19 Million cells) Surface remesher, Trimmed cell mesher, Prism layer mesher Default controls:- Base size- 36 mm, Prism layers- 4, Surface curvature- 55 points, Max cell size- 1mt Custom Surface controls:- 1. Ground- Prism layers disabled, 2. Wind tunnel - target & min size- 1mt 3. Vehicle body surface size- 15mm, prism layers- 6, wake refinement Physics models- Steady, 3D, Segregated flow, Gas, Constant density, RANS, Turbulent, K-omega, SST (Mentor) K-omega, All Y+ wall Treatment. Simulation conditions- Rotating tires with Slipping ground, Inlet velocity- 30ms, Tire rotations- 88.12 rad/s, Results- (2100 iterations @ 8 hrs) Cd- 0.27, Cl- 0.17 I'm confused with the results that for such a larger body, the Cd is 0.27. I have posted the Residuals, Reports plot pictures. Please have a look and and correct me.
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Hello, I will suggest to you k-epsilon if you are not interested to investigate the vortex behing the car. if you are interested, you have to choose k-omega, as it has be already suggested. You can find interested facts in the paper " Mesh Optimization for Ground Vehicle Aerodynamics". Here the link:www.issres.net/journal/index.php/cfdl/article/viewFile/63/43
Hi, I want to use a function for turbulent constant Cmu, however, field function is not be chosen for turbulent constants. Is there any way to do it in star-ccm+?
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Hi Jinsoo, I dont know what star-ccm+ means, a software package? Anyhow, I know a way to derive a relation for Cmu in dependence on the Reynolds number. But it is not for free, it needs some work, first of all reading the attached paper which is valid for Re = \infty. The next step then is a paper just in print where we further derived that theory for finite Re and even non-Newtonian fluids. But first the most elementary thing needs to be done: Reading the attachment.
Using OpenFOAM or Star CCM+
I would like to to run lifeboat dropping into the sea analyses in regular waves. If there is anyone with experience on STAR-CCM+ here who is familiar to this kind of simulations, i would really appreciate the help. Thank you.
If i need to creat a new user field , i have to invoke a wall y+. Is the value of wall y+ i invoked cell value or face value? I need to creat a new wall function by user field function to change every cell parameter. I don't know whether i can access my goal. Whether is the user field function not enougn and have to use user code? Appreciates！
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Using 'Field functions' you can get all the stored field data, both at cell centers and boundary faces. If you are only interested in Cell center values, then activate the option in user function , 'Ignore Boundary Values'. Hope it helps
In Star CCM+-tool-field function -Virtual heat transfer coefficient, I modified the reference turbulent prandtl number to 0.01 because I think it is the wall Prandtl number and I need to modify it,but it doesn't work. It seems like this modification does work on the simulation result. Then i noticed the local heat transfer coefficient. It's items are gray, I can't change any parameters here. The phenomenon just like, maybe the local heat transfer can work but i can't change any parameter here, and the virtual heat transfer coefficient doesn't work because the modification of the parameter cannot affect the result of the simulation. What' s the difference between the Local Heat Transfer Coefficient and the Virtual Heat Transfer Coefficient in Star CCM+ field function? And if i hope my modification of the virtual heat transfer coefficient can work on the result ,how should i do? If you knows the answer, please contact me as soon as possiple. Appreciates!
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The "virtual local heat transfer coefficient" is an approximation made in post-processing. This value can be computed even when your simulation does not include fluid energy. It requires you to specify, in advance, the Prandtl number, Turbulent Prandtl number and the fluid specific heat. It then uses these parameters in combination with the flow properties to compute the heat transfer coefficient *without solving the energy equation*. The 'local heat transfer coefficient' does require solving of the energy equation and is the method used internally by the energy model in the code to calculate local surface heat flux. It should be noted that the reference temperature is calculated locally on a cell-wise basis (using values from the first near-wall cell), in order to determine the temperature gradient at the wall and therefore the heat flux at the boundary. You can use the function 'heat transfer coefficient' to specify your own global reference temperature (eg freestream) and this will give a more useful indication of where heat is being transferred across a boundary.
If I want to simulate flow in a cylinder, but am taking only a quarter segment (because of symmetry), do I still specify the entire mass flow rate (assuming that is what I want to specify for inlet) or do I specify only a quarter of the total? I've simulated using periodic BC's before, but never while specifying mass flow so I wanted to be sure.
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Abhinav, you have to specify the amount which corresponds with your area. So quarter symmetry - means 1/4 of your mass flow rate, half symmetry - 1/2 of your mass flow rate. Btw if it is a simple cylinder than you better use wedge geometry or even 2D with axisymmetry. Victor.
I know how to set turbulent prantl number in Star CCM+,but i have no idea to set the wall prandtl number. If use FLUENT, we can set like this:modle-viscous model-mocel constant-wall prandtl number. If use OpenFOAM,it is more easier: 0 file- kappat file If you have any idea ,please contact me as soon as possible. Appreciate you!
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Hello Ying, giving the ratio between momentum diffusivity and thermal diffusivity (conductivity) the Prandtl number is defined not only at the wall but throughout your flow field, and can be used in CFD for computing the thermal conductivity from the values of viscosity and specific heat. You can create a user defined field function for the thermal conductivity, which is defined as <Your value for the Prandtl number> * ${DynamicViscosity} * ${SpecificHeat} and set it as an input for your thermal conductivity at the physics continua level. Regards, Christian
I am trying to see, if we can couple Bulk liquid Eulerian model with DPM model, so that it can show the transition region of bulk liquid to droplet transition in studying the internal nozzle flow dynamics. Star CD seems to have the ELSA model inbuilt in their codes.Does anyone know, whether we can implement this in FLUENT?
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Hi Mas Fawzi, STAR- CD has ELSA model, since it is a commercial code we cannot access the source codes.
Hi everyone.. My structure is an FPSO which is having a cylindrical part with a bottom opening (turret).What I want to do is to raise the water surface inside the cylinder w.r.t to the mean water level outside the structure so that the water surface inside the cylinder should produce a decaying sine shaped curve due to gravity and buoyancy effects.I have attached an image.Please check it. Can anybody help me on this? Any Star CCM+ experts? Thanks in advance.
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Hi Hariharan what you have done seems correct to me. There might be several issues that you need to pay attention to I assume that you have wave. 1) Time step size and mesh size are very important for simulation concerned with wave. It is recommend to use second order time solver and make sure the maximun CFL in the region that you are interested in is small than 0.5. 2) you may get elevation that is not of perfect sine shape which is correct since moonpool motion is not a piston motion. There is spatial variation due to pressure distribution effect. Hope you can solve this soon, otherwise I can have a look at your case if you can send me you sim file. Best Regards Saishuai
For radiator and pump simulations, which gives better results: Fluent or Star-CCM+?
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Hi, There is lot of difference in Star CCM+ simulations and Ansys Fluent simulations. But sometimes there is no difference at all! It depends upon how meshing is done and what sorts of boundary conditions are provided while solving. But still if I want to differentiate between 2 giants in CFD industry, then fluent has more user friendliness while modeling the problem whereas star CCM+ do not provide that much readiness as the media spoke person of CD-Adapco say that 'user need to know an exact problem so we just provide open environment to the user so he/she can model whichever the way user want' most of the time Star CCM+ works with Simpson's 1/3rd rule or 3/8th rule while solving the calculus part of model so the computational cost is more(sometimes you need supercomputer or core cluster computer is must) and solving time is more but results are more accurate without making assumptions. But Ansys uses statistical iterative methods (like Newton-Raphson Iterative method, or In-Situ Adaptive integral Tabulations (ISAT)) which takes less computing cost (you can use laptop or personal computer also) and also less time but results are less accurate and sometimes assumptions. Star CCM+ uses polyhedral mesh with problem adaptive hybrid cell convergence so that you don't need to waste time on meshing, but in Ansys meshing is more of kind of open environment so you need to define all sorts of meshing functions like problem and specific cell inflation, cell size etc. otherwise the final solutions may get wrong results. In the end the user needs to decide what sort of problem he or she needs to model. I have attached small comparison based article which is not regarding to your research but it may give some directions to your research. I would suggest you to use Star-CCM+ for pump simulations as the Voith Hydro in Pennsylvania uses Star CCM+ for there Turbomachinery related problems
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Comparison_between_CFD_Analysis_and_Experimenta
l_Data.pdf
Who has already used this model and for what problems?
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The information may be useful for your research An accurate description of the atmospheric boundary layer (ABL) is a prerequisite for computational fluid dynamics (CFD) wind studies. This includes taking into account the thermal stability of the atmosphere, which can be stable, neutral or unstable, depending on the nature of the surface fluxes of momentum and heat. The surface fluxes and vertical profiles of wind velocity and temperature are described by Monin–Obukhov similarity theory. The implementation of this thermally stratified atmosphere into CFD has been examined in this study by using Reynolds-averaged Navier–Stokes (RANS) turbulence models, and the commercial code STAR-CCM+. REF.1. CFD investigation of the atmospheric boundary layer under different thermal stability conditions
I have a spray model that I validated on STAR CD. This code is getting pretty old and in my lab, we want to go to STAR CCM+. I imported my mesh, put in place the parameters as in STAR CD to make validations between the two codes. However, the simulations always diverge. I checked my model item per item 6 or 7 times, tried several things (reduce time step by 5, increase inner iterations, decrease relaxation factors). I got some improvements by changing the initial conditions on the turbulence but it ended diverging as well. Is it normal to have such differences between two codes? Difference on conditions needed for the model to converge, like time step etc? Is it possible that the mesh of the first code is not adapted at all for the second one? To be clear, I understand that the differences between the two codes will bring differents sensitivity to mesh and other parameters but I would expect them to be able to run the same model, was I wrong? Thank you for your help.
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Hi, Since last time, I got some new and forgot to update my post... So today, I am able to run a simulation with a quality equal to my STAR-CD simulation but I still have to check results in details (I got to stop this activity during 6 months...). So basically, I left the mesh from STAR-CD in a corner and started with a new mesh made in STAR-CCM+ which allowed me to have a simulation running but still with "bad" convergence. I said "bad" because in reality, it is not. Indeed, in STAR-CCM+, we all got convergence problems in my lab but for different types of application. And finally, someone became aware that STAR-CCM+ was not using the classical idea of residuals we usually use. By default, it uses normalized residuals which makes impossible to reach residuals of 1e-4 or 1e-6. So turning off this normalization, it seems it solves the problem for now. When I finish my current test, I will try to use the same simulation with the STAR-CD mesh and see what happen... I will keep this thread updated!
I am simulating a multiphase flow using STAR-CCM+. I was running some tests solving the problem on one processor and I obtained residuals around 1e-5. I ran the exact same case on a cluster on 16 processors and I was able to obtain residuals of about 1e-9 for the same number of iterations. I am really surprised by the difference which is quiet significant. Does anyone have a clue about the source of this discrepancy? Could it be the MPI? PS: An other guy in my lab just had the same thing happening with a completely different application.
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I would not rule out the possibility that the difference is caused by the difference in discrete equation system between the sequential and parallel case. I do not have any idea, how parallelisation has been implemented in STAR-CCM. However, if the parallelisation involves domain decomposition, the implicit coupling between the domains is broken in parallel case and the equation system changes at the domain boundaries. Depending on the problem, the convergence characteristics may be very sensitive to the boundary conditions.
Source: https://www.researchgate.net/topic/STAR-CCM
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