inital turbulence values for unsteady species transport

-pilou · June 10, 2019, 08:22

Hi,

I'm currently facing an issue in a problem involving bith turbulence and species transport. The case is unsteady RANS.

We're simulating the injection of gas B in a volume that is initialy completely filled with gas A and completely still.

I initialized for as usual for turbulence intensity and dissipation with low values since the inital state is still but the problem is that turbulent diffusion is proportional to turbulent viscosity that is proportional to the ratio between those two values and it leads to a huge overestimation of diffusion.

What would be a good initial guess for turbulence parameters for this case ?

Best regards

LuckyTran · June 10, 2019, 23:14

For unsteady flows it's no longer an initial guess but an initial condition.

What you can do is freeze the flow and solve for the turbulence and use this as your initial condition.

June 10, 2019, 08:22	inital turbulence values for unsteady species transport	#1
-pilou New Member Join Date: Jun 2019 Posts: 1 Rep Power: 0	Hi, I'm currently facing an issue in a problem involving bith turbulence and species transport. The case is unsteady RANS. We're simulating the injection of gas B in a volume that is initialy completely filled with gas A and completely still. I initialized for as usual for turbulence intensity and dissipation with low values since the inital state is still but the problem is that turbulent diffusion is proportional to turbulent viscosity that is proportional to the ratio between those two values and it leads to a huge overestimation of diffusion. What would be a good initial guess for turbulence parameters for this case ? Best regards

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June 10, 2019, 23:14		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 66	For unsteady flows it's no longer an initial guess but an initial condition. What you can do is freeze the flow and solve for the turbulence and use this as your initial condition.