Numerical investigation of aerospike semi-cone angle and a small bump on the spike stem in reducing the aerodynamic drag and heating of spiked blunt-body: New correlations for drag and surface temperature

Abstract

Aerodynamic drag and heat reduction effectivity of the aerospike attached to the blunt-body at various aerospike semi-cone angles (θS), lateral injection from the aerospike stem, and a small bump on the aerospike stem, at different Mach number is numerically investigated. An open-source computational fluid dynamics code, i.e., rhoCentralFoam, a density-based solver in OpenFOAM is employed to solve the governing equations of supersonic turbulent flow. Menter's two-equation turbulence model, i.e., k−ω shear stress transport model is employed for turbulence modeling. A significant reduction in the total drag force (TDf) on the blunt-body is observed with the increase in aerospike θS at a fixed spike length (L)/blunt-body diameter (D) ratio for Mach 2 and 5. With the increase in θS>15° for L/D = 1 and θS>10° for L/D = 2, a significant decrease in the magnitude of coefficient of pressure is observed for Mach 5. Results show a maximum percentage reduction of 23.611% and 61.414% in TDf at L/D = 2 and θS=45° for Mach 2 and 5, respectively. Correlations are developed for the estimation of total drag force on the blunt-body and average surface temperature of the nose at Mach 2 and 5. Lateral injection substantially improves the aerodynamic heat reduction capability of the aerospike owing to the rapid expansion of the injectant in the main flow. An alternate passive technique (a small bump on the spike stem) capable of producing higher aerodynamic drag reduction compared to the active technique (i.e., lateral injection) is proposed. The small bump on the spike facilitates an early initiation of boundary layer separation and leads to the formation of a large recirculation zone ahead of the nose. Results indicate a higher reduction in aerodynamic drag with the increase in bump height (HB) compared to lateral and no injection at Mach 2 and 5. Present results have been validated with the experimental results available in the literature.