Numerical analysis of pressure oscillations over axisymmetric spiked blunt bodies at Mach 6.80

Mehta, R. C.

doi:10.1007/s001930200127

Cited by 35 publications

(20 citation statements)

References 12 publications

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“…However, Crawford [11] indicated signs of foreshock "waviness" in his experiments. Later, in their numerical reproduction of Crawford's experiments, Yamauchi et al [12] and Mehta [14] reported flow instabilities. Yamauchi et al [12] recorded a periodic variation of the drag coefficient, which was claimed to be caused by the unsteady vortices inside the recirculation zone.…”

mentioning

confidence: 97%

“…Yamauchi et al [12] recorded a periodic variation of the drag coefficient, which was claimed to be caused by the unsteady vortices inside the recirculation zone. On the other hand, Mehta [14] recorded periodic pressure variation on both spike and body surfaces, which was argued to indicate self-sustained flow oscillations. Nevertheless, no comprehensive investigation on the occurrence of flow instability around hemisphere cylindrical bodies, its cause, mechanism, and the associated range of model designs has been conducted so far.…”

mentioning

confidence: 98%

“…All models were equipped with pointed spikes with lengths ranging up to L=D 4. The experimental investigation by Crawford was reproduced numerically by a number of researchers, for example, Yamauchi et al [12], Mehta [13,14], and Asif et al [15]. Holden [5] measured the heat transfer to spiked hemisphere cylindrical models in turbulent hypersonic (M 1 10, 15) flow conditions.…”

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confidence: 98%

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Drag Reduction Using Aerodisks for Hypersonic Hemispherical Bodies

Ahmed

Qin

2010

Journal of Spacecraft and Rockets

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The main challenge facing the designers of hypersonic vehicles is the significantly high levels of pressure drag and aerodynamic heating. Although blunt noses are preferred for better heat distribution, they introduce substantial drag to the vehicle. Spikes and aerodisks proved to be efficient drag and heating reduction devices. However, for some flow conditions and model designs, the flow around spiked bodies can be unstable, which deteriorates their effectiveness. In the present study, a numerical investigation was conducted on a hemispherical body equipped with a spike of variable length and a hemispherical aerodisk of variable size in laminar hypersonic freestream conditions. A mechanism is proposed to explain the drag reduction and the cause of flow instability based on the shape of an effective body. In addition, the dependence of drag reduction on the spike's detailed design was investigated. For the models investigated in this work, an optimum aerodisk size produced the minimum drag and this optimum size was found to be inversely proportional to the spike length. Nomenclature b = arc length of half a semicircle, m C D = drag coefficient D = main body diameter, m d = aerodisk diameter, m L = spike length, m M = Mach number P = pressure, Pa q = dynamic pressure, Pa Re = Reynolds number S = surface area, m 2 s = distance along the surface, m T = temperature, K V = flow velocity, m=s = inclination of separation shock wave = specific heat ratio = efficiency of compression = inclination of the dividing streamline = dynamic viscosity, kg=m s = density, kg=m 3 Subscripts d = value inside the recirculation zone inf, 1 = freestream value o = total, stagnation value p = peak value r = reattachment value ref, = reference value

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confidence: 98%

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Drag Reduction Using Aerodisks for Hypersonic Hemispherical Bodies

Ahmed

Qin

2010

Journal of Spacecraft and Rockets

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“…. (8) the three different spike configurations. The comparisons of the drag on each of the spiked blunt body configuration (the conical, the hemispherical-disk and the flat-face) can be observed.…”

Section: Pressure Dragmentioning

confidence: 99%

“…The prime concern has been with regard to drag characteristics where effects due to spike length, spike head geometry, forward body geometry and relative spike diameter have been explored. Most of the experimental studies on spiked bodies are carried out to get effects on aerodynamic heating (3)(4)(5) and the surface pressure distributions (6)(7)(8) at supersonic and hypersonic Mach numbers (9)(10)(11)(12) . Kubota (13) has experimentally investigated the overall characteristics of the spiked blunt body configuration at hypersonic Mach numbers.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of the flow field over conical, disc and flat spiked body at Mach 6

Mehta¹

2010

Aeronaut. j.

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NOMENCLATURE C f skin friction coefficient C p specific heat at constant pressure D diameter of the blunt body, m e specific energy, J/kg F, G inviscid flux vectors H source vector M Mach number Pr Prandtl number p static pressure, Pa q heat flux, W/m 2 R radius of the blunt body, m R, S viscous vectors T temperature, K t time, s u, v velocity components, ms -1 W conservative variables in vector form x, r coordinate directions, m γ ratio of specific heats μ molecular viscosity, kg/m.s ρ density, kg/m 3 σ normal stress, N/m 2 τ shear stress, N/m 2 ABSTRACTA forward facing spike attached to a hemispherical body significantly changes its flow field and influences aerodynamic drag and wall heat flux in a high speed flow. The dynamic pressure in the recirculation area is highly reduced and this leads to the decrease in the aerodynamic drag and heat load on the surface. Consequently, the geometry, that is, the length and shape of the spike, has to be simulated in order to obtain a large conical recirculation region in front of the blunt body to get beneficial drag reduction. It is, therefore, a potential candidate for aerodynamic drag reduction for a future high speed vehicle. Axisymmetric compressible laminar Navier-Stokes equations are solved using a finite volume discretisation in conjunction with a multistage Runge-Kutta time stepping scheme. The effect of the spike length and shape, and the spike nose configuration on the reduction of drag is numerically evaluated at Mach 6 at a zero angle-of-attack. The computed density contours agree well with the schlieren images. Additional modification to the tip of the spike to get different types of flow field such as the formation of a shock wave, separation area and reattachment point are examined. The spike geometries include the conical spike, the flat-disk spike and the hemispherical disk spike of different length to diameter ratios attached to the blunt body.

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