Investigation of flow asymmetry around axi-symmetric spiked blunt bodies in hypersonic speeds

Abstract

The assumption that a zero-incidence flow around bodies of revolution is axisymmetric has been broadly adopted by many researchers, even for cases where the flow around such bodies becomes unstable. In this study, the validity of this assumption is revisited using CFD simulation. As a case study, the simulations of both stable and unstable hypersonic flows around spiked blunt bodies in 2D axisymmetric and full 3D computational domains are compared. It is found that, for the stable flow cases, the main flow features are apparently axisymmetric and the assumption is generally acceptable. However, some degree of asymmetry can be observed inside the shear layer in the separated region, causing small variation in the drag coefficient. For the unstable flow cases, the asymmetry of the flow features is much more significant. More importantly, the assumption that the flow is axisymmetric is found to overestimate the level of flow unsteadiness. The amplitude of temporal drag variation as predicted by the axisymmetric solution is higher than that predicted by the full 3D solution.

Review of wave drag reduction techniques: Advances in active, passive, and hybrid flow control

“…For unsteady flows, unsteadiness is more significant in the lateral oscillation of the shear layer in addition to a rotating wave inside the recirculation regions. 79,89,90…”

Forebody shock control devices for drag and aero-heating reduction: A comprehensive survey with a practical perspective

“…This is explained based on the level of energy of the dividing streamline [31]. In addition to lateral axisymmetric periodic motion in both modes, asymmetric circulatory periodic motion of the flow inside the shear layer was also reported [32,[41][42][43]. Pulsation mode is commonly associated with relatively short spikes (in the order of forebody diameter); the frequency of pulsating flow monotonically decreases by increasing the spike length [44].…”

“…They examined drag and aeroheating to a hemispherical forebody model equipped with various spike and aerodisk designs at Mach 6 and different incidence angles. The research group of Qin contributed with a number of numerical simulation studies on spiked bodies [30,31,42,52,60,69,87]. Drag and aeroheating reduction capabilities of a spike-aerodisk of different designs attached to a hemispherical model in a Mach 6 laminar freestream were investigated in [30,31].…”

“…Drag and aeroheating reduction objectives were found competing and the features of Pareto designs were addressed. In [42], Ahmed and Qin revisited and assessed the axisymmetry of the flow around a symmetric spiked forebody exposed to zeroincidence freestream. They concluded that a stable flow around a spiked forebody conveys a degree of asymmetry.…”

Dynamic Aerothermal Analysis of a Cone-Cylinder Flight Body

“…Zheng and Qiu [20] performed the uncertainties in aerodynamic force and heating characteristics of the wing of a hypersonic vehicle accounting for uncertain-but-bounded geometric parameters. Ahmed and Qin [21][22][23][24][25] explored extensive research on a spiked blunt body. They investigated the air-flow over the conical, disk, and flat spiked bodies and analyzed the flow asymmetry around axisymmetric spiked blunt bodies at hypersonic regimes.…”