Published online by Cambridge University Press: 20 April 2006
A new two-parameter integral method is presented which is applicable to unsteady two-dimensional laminar boundary layers whether they are separated or not. The governing equations consist of three moments of the boundary-layer equation, and the assumed velocity profiles are those of unsteady trailing-edge flow and Falkner-Skan flow with slip. The governing equation system being hyperbolic, the spontaneous generation of a singularity associated with unsteady separation is confirmed as the focusing of characteristics. The obtained results of the boundary-layer quantities as well as the generation of separation singularity are in good agreement with those of exact methods (e.g. van Dommelen & Shen 1980) for starting flows of cylinders.