Fluid flow in an axisymmetric, Sudden-Expansion Geometry

Abstract

This chapter deals with fluid flow in a Sudden Expansion Geometry for moderately high Reynolds number. Fluid flow in sudden expansion geometries, with or without solid particles, is an important technological process for many industrial and scientific applications, especially for combustion processes. For such geometries, even with moderately high values of the Reynolds number, the separated boundary-layer becomes unstable, and the flow exhibits repeated vortex formation and shedding at the corner point near the sudden expansion. The formation and persistence of large scale coherent vortex structures within turbulent wake-like regions give rise to turbulent behavior. The full time dependent Navier-Stokes equations are solved in this geometry. To resolve all the prevailing excited scales of the fluid flow, a fine staggered grid is used. The fine mesh and small time steps necessitate computation on scalable parallel machines. The chapter discusses the performance of parallel implementation and computations. It concludes that the performance of the parallel computations of the fluid flow for the present application is very encouraging as seen from the speedup curve, although millions of floating point operations per second (Mflops) and per processor performance is well below the optimal.