查看文章

This paper presents a technique used to accelerate the convergence of unsteady flows to a periodic steady state. The basis of this procedure is to assume the time period of the solution's oscillation and to transform both the solution and residual using a discrete Fourier transform. However, this paper also presents a method which iteratively solves for the time period during the process of calculating a solution. These methods are amenable to parallel processing and convergence acceleration techniques such as multigrid and implicit residual averaging. The accuracy and efficiency of the technique is verified by Euler and Navier-Stokes calculations for a pitching airfoil whose period of oscillation is forced. The capability to identify the natural frequency of oscillation is verified by Navier-Stokes calculations for laminar vortex shedding behind a cylinder where the time period of oscillation is unknown a priori. Results …