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

This investigation presents an approximate nonasymptotic theory for the Lighthill-Stewartson triple-deck model of supersonic laminar boundary-layer interaction. The emphasis of the present study is on supersonic flows in the Reynolds number range 10 4 <Re< 106, where the viscous sublayer is of comparable thickness to the inviscid interaction layer. The two principal simplifications of the lowest-order asymptotic theory, the neglect of the stream-tube divergence in the inviscid interaction layer, and compressibility effects in the sublayer, are examined in detail. Novel features of the theoretical development are the momentum integral treatment of the viscous sublayer and the separation pressure criterion used to determine its effective edge. Numerical solutions are presented for shock and wedge induced separation phenomena for Mach numbers in the range Z^A/oo^lO. The theoretically predicted interaction pressure field is in good agreement with experimental measurement. One of the interesting new results is the gradual shift from the triple-deck to the single-layer description, since the Mach number increases as predicted by the recent asymptotic analysis of Brown, Stewartson, and Williams (see Ref. 7) for hypersonic interactions. The existence of supercritical -subcritical jumps observed in single-layer integral theories for highly cooled wall flows is also examined. Present results indicate that these jumps do not occur if the wall compatibility conditions derived from the boundary-layer equations are satisfied, and the integral averaging is performed across the sublayer alone.

A nonasymptotic triple deck model for supersonic boundary-layer interaction

An analytical methodology based on the Lees-Klineberg moment integral theory for two-dimensional, laminar, hypersonic viscous interaction has been developed to evaluate the aerodynamic control surface effectiveness of hypersonic winged vehicles, such as the Space Shuttle Orbiter, during high-angle-of-attack reentry. A quasi-three-di mensional approach, i.e., a strip analysis of the vehicle planform, is used. Computed incremental aerodynamic coefficients produced by flap/elevon deflections of the Space Shuttle Orbiter correlate very favorably with wind-tunnel test data. Qualitative control effectiveness trends due to the effects of wall cooling, Reynolds number, and finite control surface chord length are discussed.

A Re-entry Control Effectiveness Methodology for the Space Shuttle Orbiter

Heat transfer—a review of 1974 literature

Equation (14) with 9 = 0 can be used to form a convenient algebraic approximation to Osborne's result.2 Equation (15) incorporates a better approximation to Eq. (12) than the one suggested (mainly because of its simplicity) in Ref. 7 and used in Ref. 3. Combination of Eq. (15) with the exact expression for the Sears function gives the asymptotically correct linearized incom- pressible result for all extreme values of k^ and k2. Conclusions

Extension of the Momentum Integral Method to Three-Dimensional Viscous-Inviscid Interactions

The momentum integral method of Klineberg is extended to allow the study of two-dimension al laminar viscous-in viscid interactions over a continuous range of wall cooling ratio. By redefining the Klineberg profile quantities, it is shown that the functions appearing in the governing differential equations become, to a good approximation, independent of wall cooling ratio. A considerable simplification of the method is thus affected and flows under nonisothermal wall conditions can be studied. Experimental comparisons are made for a wide class of body shapes which show that the method provides a good description of the major features of viscousinviscid interactions in both supersonic and hypersonic flow and is superior to other existing methods. In the light of these comparisons, some further improvements to the method are considered.

Momentum Integral Method for Viscous-Inviscid Interactions with Arbitrary Wall Cooling

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Momentum Integral Method for Viscous-Inviscid Interactions with Arbitrary Wall Cooling