Aerothermodynamic Assessment of Spiked Configuration for Drag Reduction at Hypersonic Speeds

Aerothermodynamic analysis was performed for blunt-body configurations with spikes mounted to determine drag reduction effectiveness. In-house perfect gas and chemical nonequilibrium solvers were utilized. The analysis revealed that flow separation and associated shock restructuring are responsible for drag reduction. Two vortices occurred in the separation zone for shorter spikes, whereas three vortices occurred for longer-spike simulations. The downstream shift of upstream influence location on the spike and upstream shift of flow reattachment location as well as the shock impingement point on the body surface were determined for high-enthalpy freestream conditions. These alterations in the flow field and the related reduction in separation bubble size led to a reduction of the effectiveness of the spike in reducing the drag force. About 13%-16% reduction in the effectiveness was found for the 4.0-MJ/kg case and sharp-spike mounting. The reduction of effectiveness was lower for longer spikes. These real gas effects were responsible for an increase in wave drag and friction drag for high-enthalpy flow over a spiked configuration. Therefore it is recommended to account for the real gas effects when considering a spike as a drag-reducing device. (c) 2020 American Society of Civil Engineers.