Abstract
' 1 A H E author, in conjunction with Th. von Karman, -*has recently given a new method of approximate integration of the Prandtl boundary layer equations, which was developed in order to treat cases in which separation of a laminar boundary layer might be expected. The method was developed because some doubt was felt as to the accuracy with which the well-known Pohlhausen analysis 2 would describe conditions in the neighborhood of such a separation point. Numerical calculations were carried out for certain cases involving theoretical simplifications, and very considerable discrepancies were found between the results of the new and Pohlhausen methods. The method was also used in developing a theory for the maximum lift coefficient of certain classes of airfoils. This theory gave satisfactory agreement with experiment but no direct experimental check on the boundary layer analysis itself has been given up to the present. Very recently G. B. Schubauer 4 published the results of a detailed experimental investigation carried out at the Bureau of Standards on a laminar boundary layer in which separation occurred. One of the major purposes of Schubauer's research was to test the accuracy of Pohlhausen's method, and accordingly a large series of velocity profiles through the boundary layer was determined experimentally, and compared with the corresponding series of profiles calculated according to the Pohlhausen procedure. The experimental comparison which Pohlhausen himself had carried out with his method (loc. cit.) was in connection with the flow around a circular cylinder, and it was felt that for this case the pressure rise downstream from the point of minimum pressure was perhaps too rapid to furnish a very sensitive test of the accuracy of any theory giving the location and characteristics of the separation region. Schubauer accordingly chose for his experiments an elliptic cylinder of fineness ratio 2.96:1 which was
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