Ablation onset in unsteady hypersonic flow about nose-tips with a forward facing cavity.

摘要

A forward-facing cavity is examined as a means of reducing the severe heating and delaying ablation onset at the nose-tip of a hypersonic vehicle. Whereas previous studies have concentrated on heating rates alone, the present study addresses the effect of the cavity on ablation onset times through experiments and joined flow-field/heat conduction simulations.; A viable experimental technique is developed to study ablation in the Mach 5 blow down wind tunnel at the University of Texas at Austin J. J. Pickle Research Center. This technique is utilized to determine the time to ablation onset for nose-tip configurations against which the computational technique could be compared. The computational technique included the linking of commercial computational fluid dynamic and solid body heat conduction software. Agreement between the experimental and computational ablation onset times is quite good. Thus, a benchmark is achieved in the computational technique for use in determining the flow-field physics of the complex, hypersonic flow problem.; An experimental parameter study is then undertaken to optimize the forward-facing cavity geometry, for a given nose-tip diameter, for the most delayed ablation onset. The parameters of cavity length, lip radius, and diameter are independently optimized. Numerical simulations are conducted for each parametrically optimized configuration in order to investigate the flow physics. The impact of the forward-facing cavity on the aerodynamic drag is also considered.