The data were obtained using the optical-surface indicator technique of visualizing the flow; its accuracy and reproducibility are discussed. The protuberances are immersed in the boundary layer on the wall of a supersonic wind tunnel. The relative importance of various non-dimensional groups is evaluated. The variation of primary separation distance is presented as a function of obstacle dimensions, Mach number, and Reynolds number, the last being the least significant. These results do not support some scaling laws found in the literature. An alternative correlation is proposed which applies to both small and large cylindrical protuberances. (Author).
The results of an experimental study of separation distances ahead of right circular cylinders mounted perpendicular to a flat plate are presented. The tests were conducted in a supersonic wind tunnel at a nominal test Mach number of 4.8. Turbulent boundary layer conditions existed at the cylinder mounting position. All tests were for single cylinder configurations. The cylinders tested ranged in length from 1/16 in to 1 1/2 in. and in diameter from 3/16 in. to 1 1/2 in. Experimental data were used to determine an empirical correlation between boundary layer separation distance and cylinder length. Comparison of results with other data sources showed the correlation in close agreement with previously observed boundary layer separation phenomena.
The report presents a numerical study of attached interacting supersonic turbulent boundary layers over a two-dimensional protuberance. Results are presented in terms of surface pressure, heat transfer and skin-friction distributions. These results indicate a strong effect of the size of the protuberance, Mach number, but a weak effect of Reynolds number and the ratio of wall-to-recovery temperature. The peak heating rates from a set of test cases compare well to a semi-empirical prediction method. In contradistinction to the laminar case, the turbulent recovery zone downstream of the protuberance is very short. (Author).
Detailed surface heat transfer data, oil flow, and schlieren photographs are presented for high speed flow separation ahead of finite span, forward facing steps on flat plates. Step spans were varied from three to ten times as large as the step height, and the step heights are three to four times larger than the undisturbed turbulent boundary layer thickness. Reynolds numbers, based on plate length, were approximately 15 million for both Mach 4.75 and Mach 5.04 local undisturbed flows over the flat plate surface. For these test conditions, the maximum extent of separation ahead of the step is approximately 4.4 times as large as the step height independent of step span, and peak heating rates were measured that are more than six to eight times larger than the undisturbed flow heating rates. Peak heating on the plate surface occurs slightly upstream and approximately 1/2 step height inboard of the outboard sides of the steps; the increase in peak heat transfer coefficients over the undisturbed flow values decreases with increasing step span. In addition to presenting the detailed surface heat transfer data, a plausible theoretical analysis is presented for calculating the region of turbulent boundary layer separation ahead of these finite span steps.
It was on a proposal of the late Professor Maurice Roy, member of the French Academy of Sciences, that in 1982, the General Assembly of the International Union of Theoretical and Applied Mechanics decided to sponsor a symposium on Turbulent Shear-Layer/Shock-Wave Interactions. This sympo sium might be arranged in Paris -or in its immediate vicinity-during the year 1985. Upon request of Professor Robert Legendre, member of the French Academy of Sciences, the organization of the symposium might be provided by the Office National d'Etudes et de Recherches Aerospatiales (ONERA). The request was very favorably received by Monsieur l'Ingenieur General Andre Auriol, then General Director of ONERA. The subject of interactions between shock-waves and turbulent dissipative layers is of considerable importance for many practical devices and has a wide range of engineering applications. Such phenomena occur almost inevitably in any transonic or supersonic flow and the subject has given rise to an important research effort since the advent of high speed fluid mechanics, more than forty years ago. However, with the coming of age of modern computers and the development of new sophisticated measurement techniques, considerable progress has been made in the field over the past fifteen years. The aim of the symposium was to provide an updated status of the research effort devoted to shear layer/shock-wave interactions and to present the most significant results obtained recently.
To the designer of modern high-speed aerospace vehicles, separation of the boundary layer before macroscopic surface features is an important problem. A typical feature of interest is a compression corner, or ramp. To aid in the development of comprehensive theories concerning boundary layer separation before a compression corner, a series of experimental investigations were conducted for the adiabatic flow of a supersonic compressible gas over a compression corner. Tests were conducted at free-stream Mach Numbers of 2.00 to 4.00 in increments of 0.50, at flat plate Reynolds Numbers of 0.75 x 10 to the 7th and 1.5 x 10 to the 7th, and for compression angles of 10.3 deg, 20.1 deg, 30.5 deg, and 39.9 deg. Static pressure surveys of the flow ahead of and over the compression corner were made. These measurements were supplemented by high-speed schlieren photographs and shadowgraphs. The separation of the turbulent compressible boundary layer was found to have strong dependence on both the Mach Number and the Reynolds Number. For Mach Numbers less than 3.00, the separation distance ahead of the compression corner decreased with increasing Mach Number. For Mach Numbers of 3.50 and 4.00, the separation distance increased with Mach Number. At all Mach Numbers, an increase in Reynolds Number increased the separation distance. The Reynolds Number influence was greater at the higher Reynolds Numbers. Unsteadiness in the separation geometry occurred for separation distances greater than six or eight boundary layer thicknesses. The separation was found to result from a free interaction of the flow phenomena involved. (Author).
A wall-mounted semi-cylindrical model fitted with a single wrap- around in (WAF) has been investigated numerically and experimentally, with the objective of characterizing the mean and turbulent flowfield near a WAF in a supersonic flowfield. Numerical and experimental results are used to determine the nature of the flowfield and quantify the effects of fin curvature on the character of the flow near WAFs. This research has been motivated by the need to identify possible sources of a high-speed rolling moment reversal observed in sub-scale flight tests. Detailed mean flow and turbulence measurements were obtained in the AFIT Mach 3 wind tunnel using conventional probes and cross-wire hot-film anemometry at a series of stations upstream of and aft of the fin shock/boundary layer interaction. Hot-film anemometry results showed the turbulence intensity and Reynolds shear stress in the fuselage boundary layer to be far greater on the concave side of the fin than on the convex side. Mean flow was also obtained in the AFIT Mach 5 wind tunnel using conventional pressure probes. Numerical results were also obtained at the test conditions employing the algebraic eddy viscosity model of Baldwin and Lomax. Correlation with experimental data suggests that the calculations have captured the flow physics involved in this complicated flowfield. The calculations, corroborated by experimental results, indicate that a vortex exists in the fin/body juncture region on the convex side of the fin. This feature is not captured by the oft- used inviscid methods, and can greatly influence the pressure loading on the fin near the root.
