Specific features of application of the surface flow oil film visualization in pulsed supersonic wind tunnels

Various approaches to oil film visualization of the flow on the cylinder surface aligned transversely in a supersonic flow in a pulsed wind tunnel are compared. Two types of fine-particle coloring pigments Al2O3 and TiO2 are considered. Two methods of pigment application are used: sprinkling onto the model surface pre-coated with an oil film and applying a mixture of the pigment and oil onto the model surface. The mass fraction of the pigment in the mixture for oil film visualization is varied from 10 to 20 %. Photographs of the dynamics of variation of the oil film coating on the model surface are presented, which are taken immediately after application, during the experiment, and upon its completion. Based on the results of the present study, recommendations are formulated on using surface flow oil film visualization with due allowance for specific features of application of this method for experiments in pulsed supersonic wind tunnels.