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 rengu October 25, 2007 09:38

hi everybody i would like t

hi everybody

i would like to use a steady-state solver for incompressible,turbulent flow of newtonian fluids.
What solver i have to choose or modify?

best regards

 pnguyen1 October 25, 2007 10:11

It is simpleFoam ! Danh

It is simpleFoam !
Danh

 rengu October 25, 2007 11:27

thanks I would like to use

thanks

I would like to use boundary condition of temperature or heat flux on my walls.
How can i do that?

best regards

Dear FOAMers, I am facing som

Dear FOAMers,
I am facing some difficulties in simulating the steady state, incompressible, turbolent and newtonian flow around a wing, with a Reynolds of about 250000.
After running the case in Fluent, I used the same tetra mesh and the same solver settings also in OF, since I want to compare simpleFoam with Fluent performances for this kind of analysis.
I fixed endTime = 400, since 400 timeStep are enough for Fluent to converge, although a force coefficient values rough esteem can be already seen after 20 iterations. The problem I have is that, even after 400 iteration, OF does not give me a decent value for forceCoefficient: both cd and cl oscillate around a value and cl gives negative values that are not expected.

This is in brief my case set up.
The entire domain is shaped as a half-sphere, the wing is placed somewhere at about 1/3 of the diameter, the mean chord is 0.2539 and the area 0.1225. As said, I have a tetra grid with about 450000 cells. After fluentMeshToFoam, checkMesh gives me an OK for every check, no warning nor "odd values". I applied the following boundary conditions:

- inlet: velocityInet, v (15, 0, 0), p zeroGradient, k = 0.001, epsilon = 0.000616218,
- wall: v (0,0,0), p, k and epsilon zeroGradient,
- symmetry plane for the central plane,
- internalField with the same values as the inlet, a part from p = 0,
Numerical values for k and epsilon are Fluent converged values. There is no outlet, since the domain is half a sphere.

I used realizableKE model, with coefficient standard values. I added wall roughness as explained here and used Ks = 0.0004 m and Cs = 0.5. controlDict is modified only to include forceCoeff calculation, fvScheme and fvSolution are as taken from simpleFoam pitzDaily tutorial.

I tried to run simpleFoam without turbolence for 50 iterations and then turn the turbolence on (as suggested on other threads) with the result that oscillating frequency is a bit lower, but no real improvement in my solution.

At the moment, I really have no idea where the problem with my solver set up can be or if it could be a mesh problem (although it was ok with Fluent). Is there anyone that can help me to understand what is wrong with my case? Or where and how my case set up can be improved?

Thanks a lot.

I noticed that simpleFoam boun

I noticed that simpleFoam bounds epsilon and k value at every time step:

Time = 98

DILUPBiCG: Solving for Ux, Initial residual = 0.000327038, Final residual = 7.4949e-07, No Iterations 5
DILUPBiCG: Solving for Uy, Initial residual = 0.000459395, Final residual = 3.47802e-07, No Iterations 4
DILUPBiCG: Solving for Uz, Initial residual = 0.000990822, Final residual = 3.02104e-07, No Iterations 5
DICPCG: Solving for p, Initial residual = 0.0150655, Final residual = 9.19434e-07, No Iterations 64
DICPCG: Solving for p, Initial residual = 0.00208363, Final residual = 9.62087e-07, No Iterations 46
DICPCG: Solving for p, Initial residual = 0.000381863, Final residual = 9.45239e-07, No Iterations 23
time step continuity errors : sum local = 2.98896e-08, global = -5.78346e-17, cumulative = -7.87968e-16
DILUPBiCG: Solving for epsilon, Initial residual = 0.000210108, Final residual = 2.25794e-07, No Iterations 6
bounding epsilon, min: -0.000375018 max: 26.017 average: 0.0375668
DILUPBiCG: Solving for k, Initial residual = 0.00401514, Final residual = 8.42231e-07, No Iterations 5
bounding k, min: -0.000499552 max: 0.0870239 average: 0.0022416
ExecutionTime = 867.71 s ClockTime = 868 s

Time = 99

DILUPBiCG: Solving for Ux, Initial residual = 0.000326683, Final residual = 7.82376e-07, No Iterations 5
DILUPBiCG: Solving for Uy, Initial residual = 0.00045872, Final residual = 3.02211e-07, No Iterations 4
DILUPBiCG: Solving for Uz, Initial residual = 0.000984986, Final residual = 3.11912e-07, No Iterations 5
DICPCG: Solving for p, Initial residual = 0.0150719, Final residual = 8.5828e-07, No Iterations 65
DICPCG: Solving for p, Initial residual = 0.00208536, Final residual = 9.54952e-07, No Iterations 46
DICPCG: Solving for p, Initial residual = 0.000382316, Final residual = 9.15322e-07, No Iterations 25
time step continuity errors : sum local = 2.90892e-08, global = -1.59763e-17, cumulative = -8.03944e-16
DILUPBiCG: Solving for epsilon, Initial residual = 0.000208569, Final residual = 2.23786e-07, No Iterations 6
bounding epsilon, min: -0.000318775 max: 26.3163 average: 0.0381974
DILUPBiCG: Solving for k, Initial residual = 0.00408402, Final residual = 3.85058e-07, No Iterations 6
bounding k, min: -0.000395934 max: 0.0886006 average: 0.0022516
ExecutionTime = 884.53 s ClockTime = 884 s

Time = 100

DILUPBiCG: Solving for Ux, Initial residual = 0.000326456, Final residual = 7.52399e-07, No Iterations 5
DILUPBiCG: Solving for Uy, Initial residual = 0.000458207, Final residual = 9.26749e-07, No Iterations 3
DILUPBiCG: Solving for Uz, Initial residual = 0.000979169, Final residual = 4.38241e-07, No Iterations 5
DICPCG: Solving for p, Initial residual = 0.0150712, Final residual = 9.37326e-07, No Iterations 65
DICPCG: Solving for p, Initial residual = 0.00208234, Final residual = 9.76389e-07, No Iterations 46
DICPCG: Solving for p, Initial residual = 0.000382391, Final residual = 9.66883e-07, No Iterations 25
time step continuity errors : sum local = 3.08522e-08, global = 4.86743e-17, cumulative = -7.5527e-16
DILUPBiCG: Solving for epsilon, Initial residual = 0.000201526, Final residual = 2.13926e-07, No Iterations 6
bounding epsilon, min: -0.000314675 max: 26.5883 average: 0.0388024
DILUPBiCG: Solving for k, Initial residual = 0.00396182, Final residual = 1.81276e-07, No Iterations 6
bounding k, min: -0.000382426 max: 0.0900658 average: 0.00226091
ExecutionTime = 904.56 s ClockTime = 904 s

I tried to decrease of two order of magnitude k and epsilon initial guess, but nothing changed. I really need your help...