Parametric Experimental Studies on Supersonic Flow Unsteadiness over a Hemispherical Spiked Body
Devabrata Sahoo, S. K. Karthick, Sudip Das, Jacob Cohen
Abstract
Experimental studies are carried out to investigate the effects of the geometrical parameters with a drag reducing spike on a hemispherical forebody in a supersonic freestream of at 0 deg angle of attack. The spike length (, 1.0, 1.5, 2.0), spike stem diameter (, 0.12, 0.18), and spike tip shapes are varied, and their influence on the time-averaged and time-resolved flowfield is examined. When increases, a significant reduction in drag is achieved at , whereas the variation in has only a minor effect. The intensity of the shock-related unsteadiness is reduced with an increase in from 0.06 to 0.18, whereas changes in have a negligible effect. The effects of spike tip geometry are studied by replacing the sharp spike tip with a hemispherical one having three different base shapes (vertical base, circular base, and elliptical base). A hemispherical spike tip with a vertical base is performing better by reducing and flow unsteadiness. The dominant spatiotemporal mode arising due to the shock-related unsteadiness is represented through modal analysis of time-resolved shadowgraph images, and the findings are consistent with the other measurements.