Studies of Flow Topology around Hemisphere at Transonic Speeds Using Time-Resolved Oil Flow Visualization

Abstract

This paper presents the results of the study of surface flow topology over a hemisphere using time-resolved oil flow visualization at a range of Mach numbers between 0.2 and 0.7. Several cameras were used to simultaneously record temporal evolution of oil luminescence on and around the hemisphere. Perspective Transformation Matrix technique was used to reconstruct the spatial distribution of oil luminescence over the “virtual” surface; this approach allows studying oil flow visualization patterns from angles, not directly accessible in the experiment. The separation region downstream of the hemisphere was found to continuously decrease with the increasing Mach number and a formation of a large vortical structure at the separation line near the bottom of the hemisphere was observed at M = 0.7.