[FreeFlyer]

Hi there,

I'm currently writing a thesis about the development of a propeller design for an aircraft. To evaluate my design I did a recalculation with Ansys CFX 20R1. Now, analysing the result with CFX-Post, I want to know where flow separation takes place on the blade's surface. Apparently you normally use the skin friction coefficient C_f as an indicator. The problem is that I can't find it in even though Ansys lists it in its CFX-Post manual in the variable list. As a workaround I defined the expression for the skin friction coefficient: "Wall Shear/(o.5*Density*Velocity^2)", and plotted it over the blade's surface. But the result was all positive even though I know from plotting streamlines and vectors that there is flow separation happening and so the coefficient should be negative.
My next step in troubleshooting was to plot just the Wall Shear - if I understand it correctly it's the parameter which causes the skin friction coefficient to become negative. But also the Wall Shear is all positive.
So I wonder if there's a direct way of plotting the skin friction coefficient or if I could work around it with some formula? If it's just possible using a formula I wonder if I already use the right one and if I did some error? Is my understanding of the variable Wall Shear wrong?

I would be glad for every hint,
Thanks.