Search NASA⌕ Search

Engineering topics

Bertin, J. J.

Publications and source records attributed to Bertin, J. J..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Shuttle orbiter boundary layer transition at flight and wind tunnel conditions

Hypersonic boundary layer transition data obtained on the windward centerline of the Shuttle orbiter during entry for the first five flights are presented and analyzed. Because the orbiter surface is composed of a large number of thermal protection tiles, the transition data include the effects of distributed roughness arising from tile misalignment and gaps. These data are used as a benchmark for assessing and improving the accuracy of boundary layer transition predictions based on correlations of wind tunnel data taken on both aerodynamically rough and smooth orbiter surfaces. By comparing these two data bases, the relative importance of tunnel free stream noise and surface roughness on orbiter boundary layer transition correlation parameters can be assessed. This assessment indicates that accurate predications of transition times can be made for the orbiter at hypersonic flight conditions by using roughness dominated wind tunnel data. Specifically, times of transition onset and completion is accurately predicted using a correlation based on critical and effective values of a roughness Reynolds number previously derived from wind tunnel data.

Goodrich, W. D.↗
NASA NTRS1983

Shuttle Orbiter boundary-layer transition - A comparison of flight and wind tunnel data

Hypersonic boundary-layer transition data obtained on the windward centerline of the Shuttle Orbiter during entry for the first four flights are presented and analyzed. Because the Orbiter surface is composed of a large number of thermal protection tiles, the transition data include the effects of distributed roughness arising from tile misalignment and gaps. These data are used as a benchmark for assessing and improving the accuracy of boundary-layer transition predictions based on correlations of wind tunnel data taken on both aerodynamically rough and smooth Orbiter surfaces. By comparing these two data bases, the relative importance of tunnel free-stream noise and surface roughness on Orbiter boundary-layer transition correlation parameters can be assessed. This assessment indicates that accurate predictions of transition times can be made for the Orbiter at hypersonic flight conditions by using roughness dominated wind tunnel data. Specifically, times of transition onset and completion can be accurately predicted using a correlation based on critical and effective values of a roughness Reynolds number previously derived from wind tunnel data.

Goodrich, W. D.↗
NASA NTRS1981

Comparison of correlations of Shuttle boundary-layer transition due to distributed roughness

The transition criteria for the windward surface of the Shuttle Orbiter, which is composed of a large number of thermal protection tiles, must include the effect of distributed roughness arising from joints and possible tile misalignments. Theoretical flow-field parameters and heat-transfer distributions were used to analyze boundary-layer transition data. Data were obtained for Mach numbers from 8 to 12 over a Reynolds number range from 1.8 million to 17.6 million with surface temperatures from 0.114 to 0.435 T sub t. The transition correlations were approximately the same both for the misaligned-tile models and for the grit-roughened model. The incipient value Re sub K, tr was 15, the critical value was 85, the effective value was 190.

Bertin, J. J.↗
NASA NTRS1980

Aerodynamic heating for gaps in laminar and transitional boundary layers

The presence of gaps, slots, and/or steps in a surface may significantly perturb a supersonic boundary layer. The paper discusses heat-transfer distributions for a variety of gap configurations which were obtained by placing instrumented inserts in a flat-plate structural carrier. The data were obtained in a 3.50 foot hypersonic wind tunnel at a freestream Mach number of 5.10 over a range of Reynolds number from 2,570,000 to 8,110,000. The variables of the test program included the freestream Reynolds number and the gap configuration, e.g., width, depth, step height, number, and orientation.

Bertin, J. J.↗
NASA NTRS1980

Variable-grid-size transformation for solving nonsimilar laminar and turbulent boundary-layers

A numerical code has been developed to calculate nonsimilar boundary-layers (either laminar, transitional, or turbulent). The formulation of the equations of motion employs two transformations for the y-coordinate which provide a dense spacing of points near the wall and, therefore, can provide engineering solutions using relatively few points in the y-direction. The turbulent viscosity is correlated in terms of a length scale, which is in turn a function of the physical y-coordinate and of the mean-flow velocity gradient at that point. The boundary-layer solutions computed using the present code are compared with theoretical solutions presented by other investigators and with data from the literature. Comparisons with the data indicate that the theoretical solutions provide suitable values for the pitot-pressure profiles and the displacement thickness. Significant differences exist in the one comparison between the theoretical and the experimental heat-transfer rates for hypersonic flow past a flat plate.

Bertin, J. J.↗
NASA NTRS1978

The effect of the transport property models on the shuttle boundary layer

Theoretical solutions for the nonsimilar, laminar boundary-layer were computed for four points along the shuttle entry trajectory. Since the boundary layer is that region of the flow field where the effects of viscosity and of thermal conductivity are most important, numerical solutions for the boundary layer were generated using different models for the transport properties. These solutions indicate that the displacement thickness and the heat-transfer rates are very sensitive to changes in the models for thermal conductivity and for specific heat. Thus, the solutions are sensitive to the assumed transport-property model.

Bertin, J. J.↗
NASA NTRS1978

Effect of step and/or gap tile misalignment on shuttle transition

The effect of tile misalignment, simulating both step type and gap type misalignment was determined on transition locations in the plane of symmetry of the shuttle orbiter. Data were obtained in a closed circuit hypersonic tunnel with a 50-in. diameter test section providing a Mach number of 8 over a range of pressure levels from 345,000 N/sq m (50 psi) to 620 million N/sq m (900 psi). The stagnation temperature is sufficient to avoid air liquefaction in the test section.

Bertin, J. J.↗
NASA NTRS1978

The analysis of a nonsimilar laminar boundary layer

A computer code is described which yields accurate solutions for a broad range of laminar, nonsimilar boundary layers, providing the inviscid flow field is known. The boundary layer may be subject to mass injection for perfect-gas, nonreacting flows. If no mass injection is present, the code can be used with either perfect-gas or real-gas thermodynamic models. Solutions, ranging from two-dimensional similarity solutions to solutions for the boundary layer on the Space Shuttle Orbiter during reentry conditions, have been obtained with the code. Comparisons of these solutions, and others, with solutions presented in the literature; and with solutions obtained from other codes, demonstrate the accuracy of the present code.

Stalmach, D. D.↗
NASA NTRS1977

Effect of surface cooling and roughness on transition for the Shuttle Orbiter

An analysis of roughness-induced boundary-layer transition examines the sensitivity of the Orbiter boundary-layer transition criteria to surface cooling, to surface roughness, and to the assumed flow-field model. The experimental data were obtained using a 0.0175-scale Orbiter with surface roughness represented by misaligned heat-shield tiles for surface temperatures from 0.12 stagnation temperature (a value typical of entry conditions) to 0.42 stagnation temperature (a value typical of continuous-flow wind-tunnels). Tile misalignment had only a slight effect on the heat transfer and on the trasition locations for wall temperature = 0.42 stagnation temperature. Cooling the boundary layer caused the tile-induced disturbances to increase significantly, promoting premature transition. Correlation of the effects of the misalignment height and of surface cooling in promoting transition are presented and predictions are made for typical Orbiter entry conditions.

Bertin, J. J.↗
NASA NTRS1977

Effects of surface cooling and of roughness on the heating (including transition) to the windward plane-of-symmetry of the shuttle orbiter

The theoretical heat-transfer distributions are compared with experimental heat-transfer distributions obtained in Tunnel B at AEDC using a 0.0175 scale model of the space shuttle orbiter configuration for which the first 80% of the windward surface was roughened by a simulated tile misalignment. The theoretical solutions indicate that thinning the boundary layer by surface cooling increased the nondimensionalized value of the local heat-transfer coefficient. Tile misalignment did not significantly affect the heat-transfer rate in regions where the boundary layer was either laminar or turbulent.

Bertin, J. J.↗
NASA NTRS1976

Engineering flowfields and heating rates for highly swept wing leading edges

An engineering flow model is developed (and verified experimentally) which describes the flowfield that arises when a supersonic stream encounters a wedge/cylinder configuration whose angles are such that the flow includes only weak shock waves. A numerical code using the perfect gas relations is used to describe the flow in the plane of symmetry inboard of the shock interaction region. Theoretical surface-pressure and heat-transfer distributions are computed for freestream velocities ranging from 1167 to 7610 m/sec. Nondimensionalization of the heat-transfer rates in terms of local flow parameters produced a correlation of Stanton number as a function of the local Reynolds number, which is independent of the freestream flow conditions and of the surface temperature.

Bertin, J. J.↗
NASA NTRS1976

Effects of surface temperature and Reynolds number on heat transfer to the Shuttle Orbiter leeward fuselage

Heat-transfer data obtained at hypersonic shock tunnel conditions and three-dimensional flow field computations were used to study the influence of surface temperature and Reynolds number on the heating experienced by the leeward fuselage area of the Space Shuttle Orbiter configuration. The basic results of this study indicate that systematic variations in the average total enthalpy within a boundary layer (as obtained through controlled nonadiabatic processes) has an influence on the heat transfer to downstream areas which can be correlated; even in three-dimensional separated flow areas. Specifically, the average separated-flow Stanton number for the fuselage leeward surface is shown to be moderately dependent on the windward-wall to free-stream total temperature ratio.

Bertin, J. J.↗
NASA NTRS1976

Hypersonic heat-transfer and transition correlations for a roughened shuttle orbiter

The effect of roughness on the heat transfer distributions and the transition criteria for the windward pitch plane of the shuttle orbiter at an angle of attack of 30 deg was studied using data obtained in hypersonic wind tunnels. The heat transfer distributions and the transition locations for the roughened models were compared with the corresponding data for smooth models. The data were correlated using theoretical solutions for a nonsimilar, laminar boundary layer subject to two different flow field models for the orbiter.

Bertin, J. J.↗
NASA NTRS1975

Experimental investigation of supersonic flow past double-wedge configurations

Viscous-inviscid interactions characteristic of those which occur when the fuselage-generated shock wave interacts with the wing-generated shock wave of a shuttle orbiter were studied experimentally. Surface-pressure measurements and schlieren photographs were obtained to define the flowfield generated when a Mach 4.97 stream encounters a double-wedge configuration. The deflection angles for the two wedge surfaces were such that the shock interaction pattern was either a Type-V pattern or a Type-VI pattern, as defined by Edney. The correlation between the present data and the theoretical solution for the Type-VI solution is satisfactory. The correlation between the measured Type-V shock-interaction pattern and the theoretical solution is satisfactory up to the interaction region. Downstream of the interaction the Type-V data depend primarily on the shape of the leading-edge shock wave.

Bertin, J. J.↗
NASA NTRS1975

The effect of surface temperature and Reynolds number on the leeward heat-transfer for a shuttle orbiter

The effect of windward surface temperature on the heat transfer to the leeward surface of the shuttle orbiter was investigated. Heat-transfer distributions, surface-pressure distributions, and schlieren photographs were obtained for an 0.01-scale model of the 37-0 shuttle orbiter at angles-of-attack of 30 deg and of 40 deg. Similar data were obtained for a fuselage-only configuration at angles-of-attack of 30 deg and of 90 deg. Data were obtained for various Mach numbers, Reynolds numbers, and surface temperatures.

Bertin, J. J.↗
NASA NTRS1974

Analysis of high-velocity and real-gas effects on the shock-interference pattern for delta-wing orbiters

Numerical solutions have been generated to study the two-dimensional flow field which results when supersonic flow encounters double-wedge configurations whose angles are such that a Type VI pattern occurs. Two numerical codes were developed: one which used the perfect-gas relations (including the ability to vary gamma to 'simulate' real-gas effects) and a second which incorporated a Mollier table to define equilibrium air properties. Theoretical surface-pressure and heat-transfer distributions in the interaction perturbed region along the simulated 'wing-leading edge' were obtained for velocities from 1167 m/sec to 7610 m/sec.

Bertin, J. J.↗