Application of Particle Image Velocimetry to a Small-Scale de Laval Nozzle

Abstract

The application of particle image velocimetry (PIV) to a Mach 1.4 de Laval expansion nozzle is described. Velocity measurements are taken inside and outside the nozzle and are compared to schlieren data. The PIV technique is shown to resolve a normal shock inside the nozzle and underexpanded shock cell structures outside the nozzle in the open jet with a maximum spatial resolution of 0.54 mm, which is higher than has previously been achieved. A Reynolds-averaged computational fluid dynamics (CFD) simulation is also described and used to provide a priori data for a PIV optimization method previously published by the authors. The instantaneous PIV measurement of the steady normal shock, inside the nozzle, is shown to achieve reasonable agreement with the CFD prediction within experimental limits. Problems encountered at the recording stage with respect to seeding contamination of the viewing area are also highlighted, and a solution using an alternative seeding method is described