Determination of three-dimensional flow separation using measured pressure distribution

Measured pressure distributions are used to determine the vortex-type, three-dimensional flow separation by the streamline method. The line of separation is determined approximately by the loci of colliding streamlines at the edge of the boundary layer. A prolate spheroid at various flow conditions is considered as a test case. Numerical results are compared with limiting streamline patterns of the same experiment from which the pressure data are taken. Good agreement is found, particularly in the turbulent, high-incidence case where both primary and secondary separations are detected. The results suggest that the onset of a vortex-type separation requires that not only the wall limiting streamlines converge but also those at the edge of the boundary layer collide. The appearance of the former does not warrant a flow separation that creates a vortex flow.