Steady and Transient Analysis of Flows Exhibiting Strong Viscous/InviscidInteraction (Composite RNS Procedures)

摘要

The Reduced Navier-Stokes (RNS) formulation for viscous-inviscid interactingflows with significant upstream or 'elliptic' effects has been applied for transient flows in inlets and steady two and three dimensional flows over cone-cylinder flare, afterbody and channel configurations. The solution technique allows for shock-boundary layer interaction and for regions of axial and secondary flow recirculation. It has been demonstrated that for laminar flows there exists a critical Reynolds number above which the solution exhibits a breakdown. This behavior, which occurs in the region of recirculation and can be correlated with the transition location, is grid dependent and can be missed with insufficiently refined grids or when artificial viscosity is introduced. The pressure-split RNS procedure is a special form of flux-vector splitting that has very favorable properties for sharp shock-shock and shock-boundary layer interaction. A sparse matrix direct solver procedure has been applied for both two dimensional transient flows, and for three dimensional steady flows. A domain decomposition multigrid procedure has further developed for viscous interacting flows, where significant grid stretching is required in discrete flow regions.