Surface measurements on sharp flat plates and wedges in low-density hypersonic flow.

Abstract

Abstract : Measurements of surface pressure, skin friction, and heat transfer are presented for sharp flat plates at zero angle of attack and at large and small wedge angles in a hypersonic flow. These data largely span the transition from continuum to near-free-molecule flow. The magnitude of slip velocity and energy jump at the surface are inferred from the data. The inferred slip velocity compares favorably with independent measurements by other investigators of slip velocity obtained with pitot probes. The data are compared with relevant theories ranging from the continuum to the free-molecule flow regimes and are used to check the validity of Reynolds analogy. The flat plate data at zero angle of attack are in good agreement with continuum theory when the appropriate Chapman-Rubesin constant is used, and the data are in reasonable agreement with available theories in the viscous layer regime. Heat transfer data are presented which completely define the transition to the free-molecule limit. The data obtained at large wedge angles agree reasonably with viscous shock layer theory which spans the transition from continuum to near-free-molecule flow. Discrepancies appear to be traceable to assumptions in the theory regarding Prandtl number, the Chapman-Rubesin constant, and boundary-layer displacement effects. Data obtained at small wedge angles compare favorably with theory in the continuum limit. Low-density departures of pressure from continuum theory are predicted reasonably by a momentum integral theory. (Author)