A SPECTRAL TIME DISCRETIZATION FOR FLOWS WITH DOMINANT PERIODICITY

An accurate and efficient treatment of periodic and quasi-periodic flo ws based on the temporal Fourier decomposition of the Navier-Stokes eq uations is suggested. A numerical implementation for a laminar afterbo dy wake in a 2D channel is presented. This implementation is formulate d in primitive variables and uses an ordinary second-order accurate fi nite volume space discretization combined with a standard pressure cor rection procedure. A multistep time marching scheme for numerical and physical transients is developed. For flows with a variable dominant p eriod, a period correction algorithm is used. The transients character izing the instability development are simulated. The numerical results obtained for the afterbody wake confirm the expectations concerning t he efficiency and high time accuracy of the method. Moreover, the meth od provides direct access to quantities difficult to obtain by other m ethods such as the envelope and the angular velocity variation of the unstable mode. (C) 1995 Academic Press, Inc.