Hypersonic laminar computations of separated flows with account of real gas effects

Oswald, Jay; Demargne, A. A. J.; Bousquet, Jean-Marc

doi:10.2514/6.1995-2271

Cited by 3 publications

(4 citation statements)

References 2 publications

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“…Internal mechanisms are not necessarily negligible, but they either act in the same direction or are weaker than the external mechanism. The decrease in L sep found by Brenner et al 42 and by Oswald et al 43 for equilibrium hyperboloid-flare flow, with nondissociated free stream, is not so easily explained by external mechanisms. Though an axisymmetric configuration, the hyperboloid flare has flow-deflection angles similar to the geometry in Fig.…”

Section: Relation To Previous Resultsmentioning

confidence: 59%

“…45 When there is negligible dissociation upstream of reattachment ͑see Furumoto et al 45 or Grasso and Leone 17 ͒, the decrease in L sep may be due to lower pressure in region 3 caused by dissociation behind the reattachment shock. An explanation is not so obvious for the results of Oswald et al, 43 Brenner et al, 42 or Kordulla et al, 44 all of whom compared frozen flow to equilibrium flow on the hyperboloid flare. To complicate matters, the comparison by Oswald et al 43 was between an equilibrium flight condition at M ϱ ϭ25 and a perfect-gas wind tunnel condition at M ϱ ϭ10.…”

Section: Real-gas Effectsmentioning

confidence: 59%

“…An explanation is not so obvious for the results of Oswald et al, 43 Brenner et al, 42 or Kordulla et al, 44 all of whom compared frozen flow to equilibrium flow on the hyperboloid flare. To complicate matters, the comparison by Oswald et al 43 was between an equilibrium flight condition at M ϱ ϭ25 and a perfect-gas wind tunnel condition at M ϱ ϭ10. In these studies, dissociation occurs in region 1 due to the bow shock, which increases M 1 but also results in higher p 3 than for frozen flow.…”

Section: Real-gas Effectsmentioning

confidence: 59%

“…The result that separation length decreases for reacting flows relative to frozen flows was found in a number of computational studies on compression-corner flows, 17 axisymmetric hyperboloid-flare flows, [42][43][44] and shockimpingement flows. 45 When there is negligible dissociation upstream of reattachment ͑see Furumoto et al 45 or Grasso and Leone 17 ͒, the decrease in L sep may be due to lower pressure in region 3 caused by dissociation behind the reattachment shock.…”

Section: Real-gas Effectsmentioning

confidence: 93%

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Separation length in high-enthalpy shock/boundary-layer interaction

Davis

Sturtevant

2000

Physics of Fluids

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Experiments were performed in the T5 Hypervelocity Shock Tunnel to investigate nonequilibrium real-gas effects on separation length using a double-wedge geometry and nitrogen test gas. Local external flow conditions were estimated by computing the inviscid nonequilibrium flow field. A new scaling parameter was developed to approximately account for wall temperature effects on separation length for a laminar nonreacting boundary layer and arbitrary viscosity law. A classification was introduced to divide mechanisms for real-gas effects into those acting internal and external to viscous regions of the flow. Internal mechanisms were further subdivided into those arising upstream and downstream of separation. Analysis based on the ideal dissociating gas model and a scaling law for separation length of a nonreacting boundary layer showed that external mechanisms due to dissociation may decrease separation length at low incidence but depend on the free-stream dissociation at high incidence. A limited numerical study of reacting boundary layers showed that internal mechanisms due to recombination occurring in the boundary layer upstream of separation cause a slight decrease in separation length relative to a nonreacting boundary layer with the same external conditions. Correlations were obtained of experimentally measured separation length using local external flow parameters computed for reacting flow, which scales out external mechanisms but not internal mechanisms. These showed the importance of the new scaling parameter in high-enthalpy flows, a linear relationship between separation length and reattachment pressure ratio, and a Reynolds-number effect for transitional interactions. A significant increase in scaled separation length was observed in the experimental data at high enthalpy. The increase was attributed to an internal mechanism arising from recombination in the free-shear layer downstream of separation, perhaps altering its velocity profile. This real-gas effect depends on the combined presence of free-stream dissociation and a cold wall.

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Section: Relation To Previous Resultsmentioning

confidence: 59%