How to identify flow separation region?
 

I wish to know how to identify (or justify) the region where flow separation occur for external flow simulation? Is it base on the calculated pressure distribution when the readings drop to a nearly constant value (because at separation region the surface pressure is relatively lower)? or I can actually see the separation at the contour plot of pressure or streamline plot?

Your response is greatly appreciated.

Thanks Cheng

Re: How to identify flow separation region?
 

Hi Cheng,

There are a couple ways to visualize flow separation. One way is to create "Surface Streamlines" on your airfoil based on either the "conservative" velocity or the wall shear variable. This will give you an oil film effect.

Another is to create a contour plot of the component of wall shear in the direction of your main flow (i.e. the X component if your object is travelling in the X direction). You can manually specify the color range to in the positive or negative range of values, thus identifying where the flow is reversed.

A third method that may work and allows you to identify the 3D separated region is to create an isosurface or isovolume of total pressure. Total pressure will generally be lower in the separated region due to the associated losses. You could similarly plot isosurfaces of flow which has a negative velocity in your streamwise direction, although that may not capture the entire separated region.

Regards, Robin

Re: How to identify flow separation region?(Robin)
 

Thanks a lot Robin. I'll find out which of these works the best in my case.

Regards Cheng