Drag prediction of ellipse
 

I am trying to make some drag and lift measurements for an ellipse at various angles of attack ranging from 0 degrees to 90 degrees. Obviously there is a very large separated region behind the ellipse for several angles of attack. Drag measuremts agree with the experiment conducted quite well for 0,15, and 30 degrees but then start to veer off pretty significantly after that. I did notice that by the time I get to 90 degrees it is almost double the experiment. I am using kw-sst for this setup. Is there something I could be missing? The values are almost exactly double for higher aoa. Any help would be appreciated.