Problem with turbulent models

mech5190 · April 27, 2009, 10:49

I have made a model of hydrofoil and i try to run Fluent. I use SIMPLE algorithm and my problem is that run right only with allmaras turbulent model. Why dont it run with other turbulent model?? Must i change something (example: under relaxation factors?? and how??) . I note that i have use boundary layer with first line 3e-06 lenght, in Gambit.

vishyaroon · April 27, 2009, 14:18

Can you be more specific as to what problems you have with the other models? Is it a problem with running or with the results you get?

As a side note, for external flows SA turbulence model works well as compared to other turbulence models.

mech5190 · April 27, 2009, 15:44

yes, i will explain you. With other turbulent model i dont take a logical results. I don have issue for no conergence but for results.
For example i run my model with allmara and after 300-400 iterations with SIMPLE and default under relaxation factors, i take a good results (right distribution of pressures) and convergence. However, when i put k-w turbulent model, i dont take something logical (sparse eddies)...

Maybe, must i change the under relaxation factors for using k-w??

vishyaroon · April 27, 2009, 16:02

Is your flow encountering massive separation? If not the pressure should not be as sensitive to your turbulence model. Has the solution converged with the k-omega model?

mech5190 · April 27, 2009, 16:06

have you msn?? for we talk more easy?

April 27, 2009, 10:49	Problem with turbulent models	#1
mech5190 New Member Kostas Join Date: Mar 2009 Posts: 23 Rep Power: 17	I have made a model of hydrofoil and i try to run Fluent. I use SIMPLE algorithm and my problem is that run right only with allmaras turbulent model. Why dont it run with other turbulent model?? Must i change something (example: under relaxation factors?? and how??) . I note that i have use boundary layer with first line 3e-06 lenght, in Gambit.

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April 27, 2009, 14:18		#2
vishyaroon Senior Member Aroon Join Date: Apr 2009 Location: Racine WI Posts: 148 Rep Power: 17	Can you be more specific as to what problems you have with the other models? Is it a problem with running or with the results you get? As a side note, for external flows SA turbulence model works well as compared to other turbulence models.

April 27, 2009, 15:44		#3
mech5190 New Member Kostas Join Date: Mar 2009 Posts: 23 Rep Power: 17	yes, i will explain you. With other turbulent model i dont take a logical results. I don have issue for no conergence but for results. For example i run my model with allmara and after 300-400 iterations with SIMPLE and default under relaxation factors, i take a good results (right distribution of pressures) and convergence. However, when i put k-w turbulent model, i dont take something logical (sparse eddies)... Maybe, must i change the under relaxation factors for using k-w??

April 27, 2009, 16:02		#4
vishyaroon Senior Member Aroon Join Date: Apr 2009 Location: Racine WI Posts: 148 Rep Power: 17	Is your flow encountering massive separation? If not the pressure should not be as sensitive to your turbulence model. Has the solution converged with the k-omega model?

April 27, 2009, 16:06		#5
mech5190 New Member Kostas Join Date: Mar 2009 Posts: 23 Rep Power: 17	have you msn?? for we talk more easy?