Experimental investigation on aerothermal effects of forward-facing cylindrical and parabolic cavity in hypersonic flow. (August 2021)

• Record Type: Journal Article
• Authors: Sudarshan, B.; Jagadeesh, G.; Saravanan, S.
• Is Part Of: Acta astronautica. Volume 185(2021)
• Page Start: 226
• Page End: 235
• Publication Date: 2021-08
• Subjects: Hypersonic flow -- Aero heating -- Forward facing cavity -- Shock standoff distance -- Unsteady heat flux -- Schlieren visualisation -- Cavity flow; Astronautics -- Periodicals; Outer space -- Exploration -- Periodicals; Astronautics; Periodicals; 629.405
• DOI: 10.1016/j.actaastro.2021.04.036
• Languages: English
• ISSNs: 0094-5765

Abstract

Abstract: Thermal protection of hypersonic vehicles is of great concern during ascent and re-entry conditions due to higher aerothermal loads. The passive forward-facing cavity is exhibited a substantial reduction of aero heating effects. The experimental studies on unsteady aspects of the flow considering the cavity geometries and heat transfer effects within the cavity are not abundant. In the present study, we investigated the heat transfer variations and nature of shock around a blunt body with cylindrical and parabolic cavity geometries. Experiments are conducted in hypersonic shock tunnels using air as the test gas for flow enthalpy conditions of 3.2 and 5.4 MJ/kg for a free-stream Mach number of 10.9 and 10.2 respectively. The cavity flow is established by verifying the measured heat flux, pressure, and shock oscillation results. The unsteady heat flux measurements and high-speed schlieren imaging is performed to study the effects. The results reveal that the flow with the parabolic cavity geometry shows a significant increase in the mean shock standoff position of about 14% and 30% compared to the blunt-nosed body, and about 7%–18% compared to the cylindrical cavity geometry, with a reduction of bow shock oscillations. As a result, a substantial reduction of heat flux about 34%–59% on the nose surface is noticed and found it is effective for mitigating the aerodynamic heating at higher flow enthalpy conditions. The flow with a cylindrical cavity geometry indicated the substantial increase in the heat flux due to the shock interaction and the significant heat flux variation in the cavity region is recognized and observed that such effects were not prevalent with the parabolic cavity geometry. Highlights: Aero heating mitigation on blunt nosed surface is studied with different cavities. The shock standoff distance is enhanced in parabolic cavity with lower heat flux. The noticeable shock interaction effect is observed for cylindrical cavity case. High frequency of oscillations and lower base pressure exists in parabolic cavity. As flow enthalpy increases higher mitigation is observed in parabolic cavity case.