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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Computation of the shock-wave boundary layer interaction with flow separation

The boundary layer concept is used to describe the flow near the wall. The external flow is approximated by a pressure displacement relationship (tangent wedge in linearized supersonic flow). The boundary layer equations are solved in finite difference form and the question of the presence and unicity of the solution is considered for the direct problem (assumed pressure) or converse problem (assumed displacement thickness, friction ratio). The coupling algorithm presented implicitly processes the downstream boundary condition necessary to correctly define the interacting boundary layer problem. The algorithm uses a Newton linearization technique to provide a fast convergence.

Ardonceau, P.↗
NASA NTRS1992

Experimental studies of hypersonic shock-wave boundary-layer interactions

Two classes of shock-wave boundary-layer interactions were studied experimentally in a shock tunnel in which a low Reynolds number, turbulent flow at Mach 8 was developed on a cold, flat test surface. The two classes of interactions were: (1) a swept interaction generated by a wedge ('fin') mounted perpendicularly on the flat plate; and (2) a two-dimensional, unseparated interaction induced by a shock impinging near an expansion corner. The swept interaction, with wedge angles of 5-20 degrees, was separated and there was also indication that the strongest interactions prossessed secondary separation zones. The interaction spread out extensively from the inviscid shock location although no indication of quasi-conical symmetry was evident. The surface pressure from the upstream influence to the inviscid shock was relatively low compared to the inviscid downstream value but it rose rapidly past the inviscid shock location. However, the surface pressure did not reach the downstream inviscid value and reasons were proposed for this anomalous behavior compared to strongly separated, supersonic interactions. The second class of interactions involved weak shocks impinging near small expansion corners. As a prelude to studying this interaction, a hypersonic similarity parameter was identified for the pure, expansion corner flow. The expansion corner severely damped out surface pressure fluctuations. When a shock impinged upstream of the corner, no significant changes to the surface pressure were found as compared to the case when the shock impinged on a flat plate. But, when the shock impinged downstream of the corner, a close coupling existed between the two wave systems, unlike the supersonic case. This close coupling modified the upstream influence. Regardless of whether the shock impinged ahead or behind the corner, the downstream region was affected by the close coupling between the shock and the expansion. Not only was the mean pressure distribution modified but the unsteadiness in the surface pressure was reduced compared to the flat-plate case.

Lu, Frank K.↗
NASA NTRS1990

A study of the unsteadiness of crossing shock wave turbulent boundary layer interactions

The unsteadiness of crossing shock wave turbulent boundary layer interactions at a nominal Mach number of 3 was examined by measuring wall pressure fluctuations using multiple, high frequency response, pressure transducers. The unsteadiness in the initial part of the interaction for all the interactions is similar to that of single fin interaction as studied by Tran and Bogdonoff (1987). However, for stronger interactions, flow downstream of the inviscid shock crossing position has a significant unsteady characteristic. In this unsteady region of the interaction, mean surface pressure rises significantly over the value obtained from the inviscid shock approximation. The energy spectrum of the fluctuating pressure signal shows a significant increase in the energy level at the higher frequencies.

Poddar, K.↗
NASA NTRS1989

Prediction of secondary separation in shock wave boundary-layer interactions

A complex three-dimensional shock-wave/turbulent boundary layer interaction at Mach 4 has been investigated experimentally and computationally, using two turbulence models with substantial refinement. With the use of a fine grid model, secondary flow separation was successfully computed, and grid changes did not improve agreement with experiment for the extent of upstream influence. The use of a non-isotropic turbulence model gave a slight improvement in upstream influence, but the size of the interaction was still significantly less than in the experiment.

Horstman, C. C.↗
NASA NTRS1991

An exploratory study of a three-dimensional shock wave turbulent boundary layer interaction in a corner

Three-dimensional shock wave turbulent boundary layer interactions in a corner have been studied at M about 3. The first phase, detailed mean wall static pressure distributions, has shown the interaction of a two-dimensional flow on one wall with the three-dimensional flow generated by a fin. Major three-dimensional effects on both flows were observed, extending from the interaction of the initial region of the three-dimensional flow and the corner. A large part of the resulting corner flow has little resemblance to either the two-dimensional or three-dimensional interacting flows.

Bogdonoff, S. M.↗
NASA NTRS1976

The structure of shock wave-boundary layer interactions in transonic flow

The structure of transonic shock wave-boundary layer interactions is studied using asymptotic analyses, for an oblique shock impinging on a flat plate boundary layer. Solutions for unseparated laminar and turbulent boundary layers are reviewed, and incipient separation of a turbulent boundary layer is considered.

Adamson, T. C., Jr.↗
NASA NTRS1989

Inception length to a fully-developed fin-generated shock wave boundary-layer interaction

An experimental study of fin-generated shock wave turbulent boundary-layer interactions confirmed previous observations that, sufficiently far from the fin apex, such interactions become conical. The inception length to conical symmetry was found to increase weakly with Mach number for Mach numbers from 2.5 to 4 and fin angles from 4 to 22 deg. For the range of interactions examined, the inception length was found to depend primarily upon the inviscid shock angle, this angle ranging from 21 to 40 deg. The behavior of the inception length with shock angle can be broadly divided into two categories. For 'weak' interactions with shock angles less than about 35 deg, the inception length decreased as the shock angle increased. For 'strong' interactions with shock angles greater than about 35 deg, the inception region was small and was approximately constant at three boundary-layer thicknesses in length. In the latter, strong interaction case, the inception length was an order of magnitude smaller than that found in the weakest interactions examined, to the extent that strong interactions were practically fully-developed from the apex.

Lu, Frank K.↗
NASA NTRSDate not supplied

Summary of Shock Wave Turbulent Boundary Layer Interaction Experiments In a Circular Test Section

A series of experiments were performed at Mach 2.5 in a 17 cm diameter circular test section to characterize an impinging/reflected shock wave turbulent boundary layer interaction generated by a cone-cylinder centerbody. The cone-cylinder centerbody generates a conical shock wave that interacts with the naturally occurring boundary layer developing on the test section wall. Three different cone angles were used in the experiment to study unseparated, incipiently separated, and separated interactions. When the cone-cylinder centerbody is positioned on the centerline, a flowfield which is two-dimensional in the mean is generated. Three dimensional interactions were also created by offsetting the cone-cylinder centerbody from the test section centerline. The results are intended to provide benchmark quality datasets for computational fluid dynamics (CFD) validation without the pitfalls inherent in rectangular configurations where corner effects prohibit a truly two-dimensional flow in the mean. The experimental measurements included surface flow visualization, wall static pressure, flowfield Pitot tube pressure, constant-voltage anemometry (CVA) normal hot-wire, and particle image velocimetry (PIV) measurements. The hot-wire measurements were used to calculate mean mass flux and total temperature profiles, mass flux and total temperature turbulence intensities, and the mass flux-total temperature correlation. The PIV measurements provide three-dimensional mean velocity measurements. Agreement between the pressure, hot-wire, and PIV measurements is established in the undisturbed upstream flowfield.

Supersonic↗
NASA NTRSDate not supplied

Summary of Shock Wave Turbulent Boundary Layer Interaction Experiments in a Circular Test Section

A series of experiments were performed at Mach 2.5 in a 17 cm diameter circular test section to characterize an impinging/reflected shock wave turbulent boundary layer interaction generated by a cone-cylinder centerbody. The cone-cylinder centerbody generates a conical shock wave that interacts with the naturally occurring boundary layer developing on the test section wall. Three different cone angles were used in the experiment to study unseparated, incipiently separated, and separated interactions. When the cone-cylinder centerbody is positioned on the centerline, a flowfield which is two-dimensional in the mean is generated. Three dimensional interactions were also created by offsetting the cone-cylinder centerbody from the test section centerline. The results are intended to provide benchmark quality datasets for computational fluid dynamics (CFD) validation without the pitfalls inherent in rectangular configurations where corner effects prohibit a truly two-dimensional flow in the mean. The experimental measurements included surface flow visualization, wall static pressure, flowfield Pitot tube pressure, constant-voltage anemometry (CVA) normal hot-wire, and particle image velocimetry (PIV) measurements. The hot-wire measurements were used to calculate mean mass flux and total temperature profiles, mass flux and total temperature turbulence intensities, and the mass flux-total temperature correlation. The PIV measurements provide three-dimensional mean velocity measurements. Agreement between the pressure, hot-wire, and PIV measurements is established in the undisturbed upstream flowfield.

compressible flow↗
NASA NTRS1973

Three-dimensional separation for interaction of shock waves with turbulent boundary layers

For the interaction of shock waves with turbulent boundary layers, obtained experimental three-dimensional separation results and correlations with earlier two-dimensional and three-dimensional data are presented. It is shown that separation occurs much earlier for turbulent three-dimensional than for two-dimensional flow at hypersonic speeds.

Goldberg, T. J.↗
NASA NTRS1991

Shock wave-boundary layer interactions in rarefied gas flows

A numerical study is presented, using the direct simulation Monte Carlo (DSMC) method, of shock wave-boundary layer interactions in low density supersonic flows. Test cases include two-dimensional, axially-symmetric and three-dimensional flows. The effective displacement angle of the boundary layer is calculated for representative flat plate, wedge, and cone flows. The maximum pressure, shear stress, and heat transfer in the shock formation region is determined in each case. The two-dimensional reflection of an oblique shock wave from a flat plate is studied, as is the three-dimensional interaction of such a wave with a sidewall boundary layer.

Bird, G. A.↗
NASA NTRS1994

Heat-transfer measurements and computations of swept-shock-wave boundary-layer interactions

An experimental and computational research program providing new knowledge of the heat transfer in swept-shock-wave/boundary-layer interactions is described. An equilibrium turbulent boundary layer on a flat plate is subjected to impingement by a swept planar shock wave generated by a sharp fin. Five different interactions with fin angles ranging from 10 to 20 deg at freestream Mach numbers of 3 and 4 produce a variety of interaction strengths ranging from weak to very strong. A foil heater generates a uniform heat flux over the flat plate surface, and miniature thin-film-resistance sensors are used to measure the local surface temperature. The heat convection equation is then solved for the heat transfer distribution within an interaction, yielding an uncertainty of about +/- 10%. These data are compared with numerical Navier-Stokes solutions that employ a k-epsilon turbulence model. A simple peak heat transfer correlation for fin interactions is suggested.

Lee, Y.↗