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Experimental studies are carried out to investigate the effects of thegeometrical parameters with a drag reducing spike on a hemispherical forebodyin a supersonic freestream of $M_\infty=2.0$ at $0^{\circ}$ angle of attack.The spike length $(l/D=0.5,1.0,1.5,2.0)$, spike stem diameter$(d/D=0.06,0.12,0.18)$, and spike tip shapes are varied and their influence onthe time-averaged, and time-resolved flow field are examined. When $l/D$increases, a significant reduction in drag ($c_d$) is achieved at $l/D=1.5$,whereas the variation in $d/D$ has only a minor effect. The intensity of theshock-related unsteadiness is reduced with an increase in {$d/D$ from $0.06$ to$0.18$}, whereas changes in $l/D$ have a negligible effect. The effects ofspike tip geometry are studied by replacing the sharp spike tip with ahemispherical one having three different base shapes (vertical base, circularbase, and elliptical base). Hemispherical spike tip with a vertical base isperforming better by reducing $c_d$ and flow unsteadiness. The dominantSpatio-temporal mode arising due to the shock-related unsteadiness isrepresented through modal analysis of time-resolved shadowgraph images and thefindings are consistent with the other measurements.

Parametric experimental studies on the shock related unsteadiness in a hemispherical spiked body at supersonic flow