Air Flow in a Separating Laminar Boundary Layer

The speed distribution in a laminar boundary layer on the surface of an elliptic cylinder, of major and minor axes 11.78 and 3.98 inches, respectively, has been determined by means of a hot-wire anemometer. The direction of the impinging air stream was parallel to the major axis. Special attention was given to the region of separation and to the exact location of the point of separation. An approximate method, developed by K. Pohlhausen for computing the speed distribution, the thickness of the layer, and the point of separation, is described in detail; and speed-distribution curves calculated by this method are presented for comparison with experiment. Good agreement is obtained along the forward part of the cylinder, but Pohlhausen's method fails shortly before the separation point is reached and consequently cannot be used to locate this point.

The work was carried out at the National Bureau of Standards with the corporation and financial assistance of the National Advisory Committee for Aeronautics.