Unsteady Separation

A numerical method is presented for calculating the unsteady laminar flow over a circular cylinder started impulsively from rest. The governing boundary-layer equations are solved using the method of series truncation and accurate results have been obtained for larger values of time than any other Eulerian coordinate method. The variation of the vorticity, displacement thickness and displacement velocity are presented. These results. in general, confirm the presence of a singularity at a given time. The value of this time agrees with the Lagrangian coordinate method of Van Dommelen and Shen but does not agree with those of Wang, Telionis and Tsahalis. Further, the results tend to support the structure of the singularity as proposed by van Dommelen and Shen.