Visualization of Vortex at Aero-Spike Root Using Hydraulic Analogy

Flow field around a cylindrical body with hemispherical nose, with and without spike was simulated in a water flow channel using water colour dyes at Froude number 6, utilizing Hydraulic analogy, equivalent to Mach 6 in gas flow, in a first-of-its-kind study. The prime focus in this work is on visualizing the formation of vortices near the stagnation area of the forebody, otherwise difficult in hypersonic wind tunnel experiments, together with observing key features distinctive to the water channel flow visualization technique. The effect of spike-nose configurations on the base region and flow field was also studied, together with discussion about observed peculiar flow features including the hydraulic jump. Two vortices of opposite family were observed on either side of the spike, with the largest for hemispherical-nose spike, closely corroborating with results from wind tunnel experiments and numerical simulations.