Aerodynamic performance of osculating-cones waveriders at high altitudes.

摘要

The steady-state aerodynamic characteristics of three-dimensional waverider configurations immersed in hypersonic rarefied flows are investigated. Representative geometries are generated using an inverse design procedure, the method of osculating cones, which defines an exit plane shock shape and approximates the flow properties of the compression surface by assuming that each spanwise station along the shock profile lies within a region of locally conical flow. Vehicle surface and flow field properties are predicted using the direct simulation Monte Carlo method, a probabilistic numerical scheme in which simulated molecules are followed through representative collisions with each other and solid surfaces, and subsequent deterministic displacement.; The aerodynamic properties of high- and low-Reynolds number waverider geometries, optimized for maximum lift-to-drag ratio and subject to mission-oriented constraints, are contrasted with results from reference caret and delta wings with similar internal volumes to quantify the relevance and advantage of the waverider concept at high altitudes. The high-Reynolds number waverider, optimized for the continuum regime at M_∞ = 4 and Re_∞ = 250 million, was the focus of recent wind tunnel testing for near on-design and off-design conditions, including low subsonic speeds. The present work extends the previous analyses into the high-altitude regime. The low-Reynolds number waverider, optimized at M_∞ = 20 and Re_∞ = 2.5 million, is studied to determine if optimization potential exists for a high-Mach number waverider at high altitudes. A characteristic length of 5 m is assumed for both waverider configurations, representative of a hypersonic missile concept. The geometries are aerodynamically evaluated over a parametric space consisting of an altitude variation of 95 km to 150 km and an angle of attack range of –5° to 10°. The effect of off-design Mach number on the performance of the high-Reynolds number waverider is also considered.; At M_∞ = 4 in level flight, from 95 km to 105 km, the lift-to-drag ratio of the volume-matched caret wing is superior to that of the osculating-cones waverider optimized for M_∞ = 4 and Re _∞ = 250 million. From 105 km to 150 km, the performance of the osculating-cones waverider is slightly superior to that of caret and delta wings due to the degree of concavity of its lower surface. At off-design conditions, the performance of the three configurations approaches a common free-molecular limit. At M_∞ = 20 in level flight, the lift-to-drag ratio of the osculating-cones waverider optimized for M_∞ = 20 and Re_∞ = 2.5 million is similar to a volume-matched caret wing, due to the caret wing's enhanced lift coefficient. At higher angles of attack, the superior drag characteristics of the osculating-cones waverider produces an increased lift-to-drag ratio over that of the reference configurations from 95 km to 120 km. At higher altitudes, the performance of the three configurations approaches a common free-molecular limit. Maximum lift-to-drag ratio does not exceed unity for the configurations studied over the chosen high-altitude parametric space, which is consistent with previous investigations. Results support the hypothesis that potential for aerodynamic optimization exists at high altitudes for realistic, volume-oriented waverider configurations.