An alternative way would be to calculate the deflection angle at which the boundary layer subjected to the inviscid pressure field separates. A rough calculation has been tried that gives the separation angle as a function of ⁠ h / r ⁠ and the Reynolds number: The results are reported on the image, e.g., 54° calculated instead of 60° measured for ⁠ h / r ⁠ = 0.25. More experiments and a more accurate boundary layer calculation would be desirable.