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

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 e ect of the cavity on ablation onset times through experiments and joined ow- eld/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 nosetip con gurations against which the computational technique could be compared. The computational technique included the linking of commercial computational uid 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 ow eld physics of the complex, hypersonic ow problem. vi An experimental parameter study is then undertaken to optimize the forwardfacing 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 con guration in order to investigate the ow physics. The impact of the forwardfacing cavity on the aerodynamic drag is also considered.