Chemically Reacting Viscous Flow Program for Multi-Component Gas Mixtures.

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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“…Viscosity was estimated using the curve fits of Blottner 79 and mixing rule of Wilke. 80 For the high-enthalpy case in Fig.…”

Section: Single-wedge Computationsmentioning

confidence: 99%

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

Davis

Sturtevant

2000

Physics of Fluids

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“…The two models considering chemistry use the Blottner model to calculate the viscosity and thermal conductivity of each species [9]:…”

Section: Governing Equationsmentioning

confidence: 99%

Chemical nonequilibrium effects in the wake of an obstacle in hypersonic boundary-layer flows

Birrer

Stemmer

2012

Progress in Flight Physics

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Various complex §ow features occur in reentry scenarios. This paper aims to investigate the in §uence of chemical nonequilibrium e¨ects on the wake of a cuboid obstacle, sized about half the boundary layer thickness, in hypersonic boundary layer §ows. The geometry here was chosen according to NASA HyBoLT experiment as explained in [1], where the basic shape is a wedge with a half angle of 6 • . The freestream §ow was chosen to have atmospheric conditions at an altitude of 42.5 km and a Mach number of 8.5. Simulations were obtained with 3 di¨erent gas models, a caloric one, one assuming chemical equilibrium, and the last considering chemical nonequilibrium. Two-dimensional (2D) direct numerical simulation (DNS) was used over the whole domain to extract in §ow pro¦les for three-dimensional (3D) DNS of a reduced domain.

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“…The semi-empirical formula of Blottner et al [27] and curve fits provided by Gupta et al [28] are used to obtain the energy transport properties. Unfortunately, for flows with bulk phenomena such as turbulent mixing, a general multi-component approach for transport properties is not available.…”

Section: Numerical Simulationsmentioning

confidence: 99%

Scaled-Up Nonequilibrium Air Plasmas

Kruger

Laux

Machala

et al. 2004

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Chemically Reacting Viscous Flow Program for Multi-Component Gas Mixtures.

Cited by 426 publications

References 4 publications

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

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

Chemical nonequilibrium effects in the wake of an obstacle in hypersonic boundary-layer flows

Scaled-Up Nonequilibrium Air Plasmas

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