CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   drag coefficients on ellipse (http://www.cfd-online.com/Forums/fluent/117509-drag-coefficients-ellipse.html)

MachZero May 9, 2013 13:41

drag coefficients on ellipse
 
Hello all,

I am working to simulate a wind tunnel experiment that has taken place with the target of predicting lift, drag, and moments. The goal here is to use angles of attack from 0-90 for a wide range of Re. As a baseline for comparison to literature, I am using a 2:1 ellipse at 0 degrees AoA from 10-90 mph.

When I use k-omega SST in the high Re range (where turbulent BL's are expected), I get Cd values which are honestly pretty reasonable. They are near the lower limit for what Hoerner says is possible. When I use SST at low Re, where I expect laminar BLs, I get a value that is far too low, and one that is on par with turbulent BL's. When I use laminar settings at Low Re, I get values near the upper limit or Hoerner's, which is good! But there is no blending between the two. I get that it is the difference between a laminar and turbulent separation bubble, but I do not know how to proceed since I either get the maximum or minimum Cd values (i.e. it is either fully turbulent or fully laminar).

I know this is not the first time someone has come across this. Does anyone have any ideas? I am using Fluent, would one of their transition models be best suited?


All times are GMT -4. The time now is 19:35.