CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   TVR (Turbulence viscosity ratio) and reversed flow (http://www.cfd-online.com/Forums/fluent/75509-tvr-turbulence-viscosity-ratio-reversed-flow.html)

Deside April 27, 2010 17:12

TVR (Turbulence viscosity ratio) and reversed flow
 
Hi All,

Can you kindly shed some light on my dilemma. I am having a multiphase transient simulation with velocity inlet BC and Pressure Outlet BC. After a few iterations, i got the messege: turbulent viscosity limited to viscocity ratio of 100 000 in.....cells. This message only lasts for a few iterarions and it dissapears for good. My simulation runs until it converges and as i am trying to simulate some specified time, i am continuing my simulation and after some time i get the message: Reversed flow in...cells...on pressure outlet but my simulation is converging with this message coming up.

My question is: Could this undermine the fidelity of my results.

Please kindly assist. Thanks, Deside!!!! :)

nstar April 27, 2010 23:17

Both are fine.
The turbulent viscosity limit warning is normally showing in beginning iterations and will be gone after certain steps. However, if this warning persists, it normally indicates an improper boundary condition setting or very bad cells somewhere.
The reverse flow warning is nothing bad. It tells you that there is working fluid flowing from a virtual outside domain back to your simulation domain through the pressure outlet boundary. You need to be careful when the reverse flow does not physically sound. For example, if you problem is water jet flow into ambient, the reverse flow can only be air while fluent assumes the reverse flow is water. this creates some inaccuracy.

Quote:

Originally Posted by Deside (Post 256551)
Hi All,

Can you kindly shed some light on my dilemma. I am having a multiphase transient simulation with velocity inlet BC and Pressure Outlet BC. After a few iterations, i got the messege: turbulent viscosity limited to viscocity ratio of 100 000 in.....cells. This message only lasts for a few iterarions and it dissapears for good. My simulation runs until it converges and as i am trying to simulate some specified time, i am continuing my simulation and after some time i get the message: Reversed flow in...cells...on pressure outlet but my simulation is converging with this message coming up.

My question is: Could this undermine the fidelity of my results.

Please kindly assist. Thanks, Deside!!!! :)


Deside April 28, 2010 04:04

Thanks astar for the responds. In my case this BC is air at atmosperic pressure which is far from the calculation domain of interest so i think the reverse flow is air as well which i think i have to be comfortable with.


All times are GMT -4. The time now is 10:42.