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Troubles in solution convergence of rotational flow

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Old   May 19, 2019, 06:01
Default Troubles in solution convergence of rotational flow
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Ahmed Alhusseny
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Hi,
I have a channel rotating about an axis parallel to channel but far from it with distance H. The channel walls are heated, and hence, centrifugal buoyancy is expected to play an important role along with Coriolis forces in the development of flow and temperature fields. I set a Rotating reference frame with using Coupled Flow and Energy solvers along with ideal gas to address the change in the air density. However, I have problems in getting the solution converged. Thus, I tried to switch to the Implicit Unsteady solver with timestep 1.e-3, but with no benefit even with reducing the Courant number value to very low levels! This problem is equal for laminar and turbulent flow regimes, i.e. Re=1000 and 10,000, respectively. can anyone help in figuring out this problem?
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Old   May 20, 2019, 04:05
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Steve
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when your solution have a problem? just started?
try to control I.C and relaxation factor..
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Old   May 20, 2019, 06:44
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I have tried different proposals. First, I used the segregated solve along with ideal gas for incompressible flow, but the residuals start to go up after a slight reduction at the beginning of the solution. I even tried to use a ramp for each of the velocity, pressure, and energy equations, but it didn't make that benefit! Then, I tried to switch the solution to coupled flow and energy, however, the solution diverges few time steps after the beginning!
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Old   May 20, 2019, 19:39
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Why do you use ideal gas for incompressible flow?? anyway.. i think it is not the reason of diverged..

if your B.C is reasonable...

try to find where is the problem in your domain..

do you use MRF method? you can try to fixmesh problem and control rotating speed.
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