AN EXPERIMENTAL STUDY OF HYPERSONIC LOW-DENSITY VISCOUS EFFECTS ON A SHARP FLAT PLATE
CORNELL AERONAUTICAL LAB INC BUFFALO NY
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Heat transfer and pressure data were obtained with sharp flat plate models at zero and large angles of attack in the CAL hypersonic shock tunnel. These high Mach number data Mach 14 to 24 extend from the classical thin boundary layer regime to near-free-molecule conditions and are discussed within the framework of existing theory. The large angle-of-attack results verify viscous shock-layer theory and define the low-density conditions where transport effects at the shock wave first become important. The data obtained at zero angle of attack are compared with theory to define the fluid mechanism that governs the low-density effects. The strong shock-wave approximations, the vorticity interaction, and the shock-wave heating effect are unimportant in this case. For the present experiments, the effects of transport processes at the shock wave are numerically small in comparison with surface slip for the sharp flat plate at zero angle of attack, and it is postulated that surface slip is the dominant low-density effect. The slip boundary conditions are discussed to demonstrate that there is a pressure jump at the surface, analogous to the classical velocity and temperature jump. This effect is evaluated using existing theories and is in qualitative agreement with the experimental data. The slip boundary conditions are examined in light of the present experiments at zero angle of attack, and it is shown that the usual firstorder boundary conditions are inapplicable for the case of a cold wall.
- Fluid Mechanics