CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   Turbulence models and boundary layer (http://www.cfd-online.com/Forums/fluent/40116-turbulence-models-boundary-layer.html)

Stanislav Kraev March 14, 2006 02:42

Turbulence models and boundary layer
 
Hi

FLUENT documentation says that for standard wall functions you should create model with Yplus in the range 30-60. How can I estimate the error for my case if Yplus is much smaller? I realized that there are a lot of areas with Yplus about 1-5. Is the result totally incorrect? And what should I do if there are a wide range of velocities in my model (0.1-5 m/s in stagnation zones and up to 40 m/s in other zones)? What turbulence model should I use? I don't think that I should greately coarse mesh in stagnation zones because I will get very big cells and geometry features will not catched. Am I right?

Thanks a lot for any help.

Razvan March 14, 2006 06:55

Re: Turbulence models and boundary layer
 
Use Enhanced Wall Treatment (EWT), it is supposed to minimise error when y+ is around 11, and extends validity of wall functions to all range of possible y+ values. BUT this is advisable to do only if mean y+ is towards 1, not 30. In your case, it is better to make a y+ adaption to get it to 1 (you say that coarsening the grid would be inappropriate), or remake the grid near the body. Then simply choose a low-Re model (like S-A or k-w [with "transitional flow" option activated]), or a high-Re model with EWT (k-e or RSM).

Razvan


All times are GMT -4. The time now is 02:44.