k-e model limits

fateme · September 9, 2009, 10:25

Hi

I'm trying to implement the k-e model in my code. The problem is I don't know what is the limiting value for k and e. In some problems the min values I use (ie:kmin=10^-6 & emin=10^-5) yield to correct answers but when the geometry is very unregular my model becomes unstable and the viscosity grows. I would rather not put an upper limit for k although I know this is conventional. Do you think I can do that or am I obliged to implement a max bound for k or viscosity?

Does anyone know of a good refrence that has discussed about the limiting values of k and e?

Thanks very much.

wooing · September 9, 2009, 14:45

I have the same situations, sometime the ratio of k/e play a big role.In my case, in some regimes, the velocity is very small and also the strain rate.. etc, and K and E are reasonable values (very small). But the eddy viscosity have a big value due to K**2/E.
Can anyone give some suggestions?

September 9, 2009, 10:25	k-e model limits	#1
fateme New Member fateme chegini Join Date: Jul 2009 Posts: 6 Rep Power: 17	Hi I'm trying to implement the k-e model in my code. The problem is I don't know what is the limiting value for k and e. In some problems the min values I use (ie:kmin=10^-6 & emin=10^-5) yield to correct answers but when the geometry is very unregular my model becomes unstable and the viscosity grows. I would rather not put an upper limit for k although I know this is conventional. Do you think I can do that or am I obliged to implement a max bound for k or viscosity? Does anyone know of a good refrence that has discussed about the limiting values of k and e? Thanks very much.

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September 9, 2009, 14:45		#2
wooing New Member Join Date: Apr 2009 Posts: 5 Rep Power: 17	I have the same situations, sometime the ratio of k/e play a big role.In my case, in some regimes, the velocity is very small and also the strain rate.. etc, and K and E are reasonable values (very small). But the eddy viscosity have a big value due to K**2/E. Can anyone give some suggestions?