UNSTRUCTURED SPECTRAL ELEMENT METHODS FOR SIMULATION OF TURBULENT FLOWS

In this paper we present a spectral element-fourier algorithm for simu lating incompressible turbulent flows in complex geometries using unst ructured quadrilateral meshes. To this end, we compare two different i nterface formulations for extending the conforming spectral element me thod in order to allow for surgical mesh refinement and still retain s pectral accuracy: the Zanolli iterative procedure and variational patc hing based on auxiliary ''mortar'' functions. We present an interpreta tion of the original mortar element method as a patching scheme and de velop direct and iterative solution techniques that make the method ef ficient for simulations of turbulent flows. The properties of the new method are analyzed in detail by studying the eigenspectra of the adve ction and diffusion operators. We then present numerical results that illustrate the flexibility as well as the exponential Convergence of t he new algorithm for nonconforming discretizations. We conclude with s imulation studies of the turbulent cylinder wake at Re = 1000 (externa l flow) and turbulent flow over riblets at Re = 3280 (internal flow). (C) 1995 Academic Press, Inc.