Abstract: The early development of the flow of an impulsively started circular cylinder through numerically solving the N-S equations in vorticity and stream function form is studied, using ADI method to solve the vorticity equation and a fast Poisson solver to solve the stream function equation(Re= 3000, 5000, 9500). The a- and B-phenomenon observed by experiments in the flow development were successively simulated. The present method is efficient and the calculated results are in good agreement with experimental data and numerical calculations given by other accurate methods.

Key words: unsteady flow, N-S equation, Numerical calculations, cylinder