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jojoFD April 20, 2021 06:23

Dynamic mesh viscosity ratio limitation problem
 
Hi,

I am simulating a closed tank of air at 200 bar pressure and 293K temperature with a small cylinder moving inside at a velocity 1m/s, using a dynamic mesh (smoothing diffusion and remeshing method).

At 1 atm pressure, my case works fine. But at 200 bar, I get a "turbulent viscosity limited to viscosity ratio of 1.000000e+05 in (a lot of) cells" warning that won't go away for the whole simulation, which is making me doubt the physics of my results. The Reynolds number is about 2e6 so highly turbulent.

I read a lot on the subject so here are a few infos:
- my mesh quality is normally not the problem
- there is no inlet boundary condition values for turbulence to correct as my domain is fully closed
- I use a coupled scheme with second order scheme
- I reduced my under relaxation factors to 0.6, and set a low turbulence intensity (0.01) and viscosity ratio (2) for the initialization as the fluid is starting the simulation fully at rest.
- I am using a k-omega SSt model with TKE outer : 1.176 / inner 1 and SDR inner 2 / outer 1.168.

I really don't know what else to do/change so if you have an idea, that would be awesome :)

Thanks a lot


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