Computation of gas flowfields in supersonic particle probes

The results of computations to predict the properties of gas flowfields in supersonic particle probe inlets are presented. In particular, a supersonic gas impinging on a thin walled cylindrical probe aligned parallel to the freestream has been analyzed. Inviscid solutions are obtained by a slight variant to MacCormack's time-dependent finite difference method. Imposing outflow boundary conditions of fixed static pressure at the probe outlet, linear extrapolation of remaining gas properties, and a reflection technique on the probe wall including the tip, reasonable agreement is demonstrated for the shock detachment distance, stagnation pressure loss and gas ingestion rate. With some spacial smoothing and initial conditions characteristic of gas properties back of the shock, the numerical method converged in reasonable computation times, yielding a shock thickness of 2.5 grid spacings with no oscillations near the shock front.