Unsteady boundary layers and separation

A method was developed to solve numerically the unsteady, two-dimensional, incompressible, boundary-layer equations with arbitrary pressure gradients, capable of integrating through the point of zero skin friction into partially reversed flow. The properties of the boundary layer flow and separation in unsteady flows are studied in detail. The path of zero skin friction and separation singularity with respect to time was determined. Comparison of the numerical results with existing analytical, numerical and experimental results was made whenever possible. It is shown that the point of zero skin friction should not be a downstream limit of the boundary layer calculation in unsteady flow. Most of the features of separation predicted by the Sears-Telionis model of unsteady separation are found to be present. Certain characteristic properties of unsteady viscous flow, like vorticity diffusion, steady streaming, etc., are also studied in detail.