Ablation Onset in Unsteady Hypersonic Flow About Nose Tip with Cavity

Silton, Sidra I.; Goldstein, David

doi:10.2514/2.6540

Cited by 20 publications

(25 citation statements)

References 7 publications

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“…Ablation in the context of hypersonic flow around vehicles and test bodies has been discussed recently by, for example, Kuntz et al (2001) (numerical calculations) and Silton and Goldstein (2000) (experimental and numerical results). The experimental results of the latter show irregular ablation (cf.…”

Section: Model Calculationsmentioning

confidence: 99%

High-Resolution Simulations of the Impacts of Asteroids into the Venusian Atmosphere II: 3D Models

Korycansky¹,

Zahnle

Low

2002

Icarus

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We compare high-resolution 2D and 3D numerical hydrocode simulations of asteroids striking the atmosphere of Venus. Our focus is on aerobraking and its effect on the size of impact craters. We consider impacts both by spheres and by the real asteroid 4769 Castalia, a severely nonspherical body in a Venus-crossing orbit. We compute mass and momentum fluxes as functions of altitude as global measures of the asteroid's progress. We find that, on average, the 2D and 3D simulations are in broad agreement over how quickly an asteroid slows down, but that the scatter about the average is much larger for the 2D models than for the 3D models. The 2D models appear to be rather strongly susceptible to the "butterfly effect," in which tiny changes in initial conditions (e.g., 0.05% change in the impact velocity) produce quite different chaotic evolutions. By contrast, the global properties of the 3D models appear more reproducible despite seemingly large differences in initial conditions. We argue that this difference between 2D and 3D models has its root in the greater geometrical constraints present in any 2D model, and in particular in the global conservation of enstrophy in 2D that forces energy to pool in large-scale structures. It is the interaction of these artificial large-scale structures that causes slightly different 2D models to diverge so greatly. These constraints do not apply in 3D and large scale structures are not observed to form. A one-parameter modified pancake model reproduces the expected crater diameters of the 3D Castalias reasonably well. c 2002 Elsevier Science (USA)

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Section: Model Calculationsmentioning

confidence: 99%

High-Resolution Simulations of the Impacts of Asteroids into the Venusian Atmosphere II: 3D Models

Korycansky¹,

Zahnle

Low

2002

Icarus

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“…However, since the focus of this work was on the stagnation region and the sonic line occurs upstream of the conical region of the projectile (i.e. the conical region does not effect the stagnation region), the projectile nose was modelled as a sphere-cylinder (Yuceil 1995 ;Engblom 1996;Silton & Goldstein 2000). Thus, the basic model geometry was a hemispherically-blunted cylinder with a streamwise cylindrical nose cavity (figure 1).…”

Section: Modelsmentioning

confidence: 99%

“…The mould was filled with distilled water and chopped fibreglass threads (see Silton & Goldstein 2000). A brass spindle was placed in the mould to extract the ice model from the mould as well as provide a base with which to attach the model to the sting adapter.…”

Section: Modelsmentioning

confidence: 99%

Use of an axial nose-tip cavity for delaying ablation onset in hypersonic flow

Silton

Goldstein

2005

J. Fluid Mech.

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A forward-facing cavity is examined as a means of reducing the severe heating and delaying ablation onset at the nose-tip of a hypersonic vehicle. Whereas previous studies have concentrated on the nature of flow-induced Hartmann-whistle oscillations or on heating rates alone, the present study addresses the effect of the cavity on ablation onset times through experiments and coupled flow field/heat conduction simulation. Using our previously developed experimental technique, a parametric study is undertaken to optimize the forward-facing cavity geometry for the most delayed ablation onset. The geometric parameters of cavity length, lip radius and diameter are independently optimized for a given nose-tip diameter. Then using benchmarked linked flow field/heat conduction simulations, numerical simulations are conducted for each parametrically optimized configuration in order to investigate the flow physics.

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“…The flow within the cavity would be oscillating (unsteady movement of shock within the cavity). If an appropriate cavity configuration is chosen, the mean surface heat-flux would be reduced because lots of heat would be taken away by the process of 'swallow' and 'spitting' caused by the oscillations [12,13].…”

Section: Introductionmentioning

confidence: 99%

Aerothermal Shape Optimization of Hypersonic Vehicle Leading Edge by Using Genetic Algorithm

Cui

Shouchao

2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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To minimize the peak heat-flux of hypersonic blunt leading-edge, the Mini-Max optimization model is introduced for the first time for aerothermodynamics optimization. The surface heat-flux is obtained by resolving Navier-Stokes equations, and only the frozen flow is considered. The computational fluid dynamics (CFD) based Genetic Algorithm is used as the optimizer. A novel 2-D profile of leading-edge is obtained and the peak heat-flux is significantly reduced. Compared to the commonly used circular leading-edge, there is a large area of high temperature, high pressure in the front part of leading-edge, together with greater shock stand-off distance. The thickness of thermal boundary layer is increased about 40% at the stagnation point, the peak heat-flux is decreased about 20% and the heat-flux distribution is little changed in the vicinity of stagnation point. The robustness analysis shows that the favorable performance of the optimal 2-D profile is universally effective, i.e., it can effectively decrease the peak heat-flux by about 20% for various wall temperatures, Mach numbers, flight altitudes and thicknesses of the leading-edge as compared with the corresponding case of circular leading-edge. Although the reduction scope of peak heat-flux decreases with the change of angle-of-attack, but the peak heat-flux can still be decreased by more than 4% when the angle-of-attack is not greater than 15°. Several axisymmetric cases are also investigated in this paper, and the circular cone is taken as the benchmark, the peak heat-flux around an axisymmetric blunt cone, which is generated by the corresponding optimal 2-D profile, is also reduced by about 25%. Similarly, the distribution of heat-flux around the stagnation point is almost unchanged. NomenclatureC p = pressure coefficient D = thickness of the leading-edge/nose-tip H = flight altitude h 0 = total enthalpy h w = wall enthalpy h ∞ = enthalpy of the free-stream flow Ma ∞ = flight Mach number P = pressure Q = heat-flux Q 0 = heat-flux of the stagnation point Q max = peak heat-flux Q(x) = heat-flux along the leading-edge R 0= curvature radius at the stagnation point T = temperature T w = wall temperature V ∞ = velocity of the free-stream flow α = angle-of-attack θ = the induced angle with respect to the x-axis φ = angle between a tangent to the surface and the free-stream direction ρ ∞ = density of the free-stream flow ∆y n = grid thickness for the first layer near the wall 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition

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Ablation Onset in Unsteady Hypersonic Flow About Nose Tip with Cavity

Cited by 20 publications

References 7 publications

High-Resolution Simulations of the Impacts of Asteroids into the Venusian Atmosphere II: 3D Models

High-Resolution Simulations of the Impacts of Asteroids into the Venusian Atmosphere II: 3D Models

Use of an axial nose-tip cavity for delaying ablation onset in hypersonic flow

Aerothermal Shape Optimization of Hypersonic Vehicle Leading Edge by Using Genetic Algorithm

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