Particle Impaction in Axially Symmetric Supersonic Flow

Abstract

The results of computations to predict the particle collection efficiency in axially symmetric supersonic flow are presented. In particular, a supersonic gas impinging on a truncated circular cylinder aligned parallel to the freestream has been analyzed. Inviscid solutions are obtained by a slight variant to MacCormack's time-dependent finite difference method. In imposing outflow boundary conditions of fixed Mach number, linear extrapolation of remaining gas properties, and a reflection technique on the cylinder walls, reasonable agreement is demonstrated for the shock detachment distance and stagnation pressure loss. It is demonstrated that the capture efficiency is influenced by particle inertia, departure from Stokes drag, and gas compressibility. By defining an effective Stokes number in terms of the particle stopping distance downstream of the shock that includes the effects of non-Stokesian drag and slip flow, and rescaling the Stokes number with the shock detachment distance, the collection efficiency is shown to be correlated with a single universal curve.