Aeroheating Uncertainties in Uranus and Saturn Entries by the Monte Carlo Method

Palmer, Grant; Prabhu, Dinesh K.; Cruden, Brett A.

doi:10.2514/1.a32768

Cited by 32 publications

(63 citation statements)

References 36 publications

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“…Quasi-steady state (QSS) rates are not implemented for H in NEQAIR so that simulations were conducted with Boltzmann distributed state populations. Comparisons to stagnation line results produced through DPLR and NEQAIR reported in our previous work [2] are also given here (Section IV.B), subject to the same limitations in NEQAIR's capability. …”

Section: B Computationalmentioning

confidence: 98%

“…Since the predictions for Saturn probe entry generally have shock stand-off distances between 2-2.5 cm [2], the EAST experiment may be considered to replicate the entire stagnation line. Two relevant points from the uncertainty study were obtained for a velocity of 27.7 km/s and density equivalent pressure of 0.49 Torr and 26.3 km/s and 0.15 Torr.…”

Section: B Comparison To Flight Cfdmentioning

confidence: 99%

“…Given the diffusion coefficients discussed above, it is reasonable to assume that the density is above this limit. Therefore, the radiance observed is only sensitive to the ratio of n 2 /n 1 , or equivalently the effective temperature, T e (1,2) . This effective temperature is shown as a function of pre-shock length in Figure 14.…”

Section: Pre-shock Excitationmentioning

confidence: 99%

“…Recently, using the state-of-the-art simulation tools at NASA Ames Research Center, uncertainties in predictive models for these entries were evaluated through Monte Carlo analysis [2]. For both cases, the uncertainty in convective heating was shown to be relatively low.…”

Section: Introductionmentioning

confidence: 99%

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Shock Radiation Tests for Saturn and Uranus Entry Probes

Cruden

Bogdanoff

2015

45th AIAA Thermophysics Conference

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Section: B Computationalmentioning

confidence: 98%

Section: B Comparison To Flight Cfdmentioning

confidence: 99%

Section: Pre-shock Excitationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Shock Radiation Tests for Saturn and Uranus Entry Probes

Cruden

Bogdanoff

2015

45th AIAA Thermophysics Conference

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“…The test conditions for the 45 o sphere-cone models in air were selected to produce convective heat transfer rates comparable to those likely to be experienced by probes entering the atmospheres of Saturn or Uranus. 33 The test conditions for the 30 o sphere-cone geometry match a condition used in previous experiments concerning boundary-layer transition due to surface roughness on conic frusta. 21 The test conditions for the 45 o sphere-cone models in carbon dioxide were selected to match velocity and ambient pressure for one of the test conditions in air, while giving similar Mach and Reynolds numbers to the test conditions in air.…”

Section: E Test Conditionsmentioning

confidence: 97%

The Effects of Surface Roughness on Turbulent Heat Transfer Measured in Hypersonic Free Flight

Wilder

Prabhu

Reda

2014

52nd Aerospace Sciences Meeting

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Experiments were conducted in the NASA Ames Hypervelocity Free Flight Aerodynamic Facility ballistic range to quantify effects of surface roughness on turbulent convective heat transfer on the frusta of spherically-blunted 30° and 45° cones. Distributed surface roughness was produced by grit-blasting the model surfaces. Each surface was characterized using 3D profilometry measurements obtained by confocal microscopy. Tests were conducted in air and in carbon dioxide at speeds between 2.7 km/s and 3.5 km/s and freestream pressures between 50 Torr and 228 Torr, resulting in stagnation-point heat fluxes between 1200 W/cm 2 and 5400 W/cm 2 . Turbulent heat transfer augmentation factors were determined on the conic frusta as ratios of rough-wall to smooth-wall measurements made at the same test conditions. Laminar and turbulent flow simulations were performed for smooth configurations at the measured test conditions and wall temperatures, from which non-dimensional correlating parameters were calculated. For the conditions tested, augmentation factors as high as 1.8 were measured and were found to correlate well with the smooth-wall roughness Reynolds number, independent of test gas. Nomenclature k � = mean roughness element height k s = sand-grain roughness height q̇ = convective heat transfer rate R N = model nose tip radius Re k = turbulent roughness Reynolds number based on smooth-wall friction velocity, ρ w u τ 0 k � /µ w Re kk = laminar roughness Reynolds number for transition, ρ k u k k � /µ w Re R N = freestream Reynolds number based on model nose radius, ρ ∞ u ∞ R N /µ ∞ s = distance along surface from apex T = temperature u = fluid velocity component parallel to the wall u τ 0 = smooth-wall friction velocity, (τ w 0 /ρ w ) 1/2 V 0 = model velocity at launch V � = average model flight velocity (= speed at mid-range) x, y, z = local surface coordinates used in surface-roughness characterization δ s = smooth-wall sublayer thickness, 11ν w /u τ 0 µ = dynamic viscosity ν = kinematic viscosity, µ/ρ ρ = fluid density σ = standard deviationThis material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. AIAA SciTech 2 American Institute of Aeronautics and Astronautics τ w = surface shear stress Subscripts e = at the boundary-layer edge k = at the mean roughness height N = on the model nose r = on rough surface s = on smooth surface w = at wall conditions 0 = on smooth surface ∞ = at freestream conditions

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