Measurements in highly dissipative regions of hypersonic flows. Part I. Hot-wire measurements in low Reynolds number hypersonic flows. Part II. The near wake of a blunt body at hypersonic speeds

• Main Author: Dewey, Clarence Forbes
• Format: Others
• Published: 1963
• Online Access: https://thesis.library.caltech.edu/5097/1/Dewey_cf_1963.pdf; https://thesis.library.caltech.edu/5097/2/Dewey_cf_1963_Fig_24.pdf; Dewey, Clarence Forbes (1963) Measurements in highly dissipative regions of hypersonic flows. Part I. Hot-wire measurements in low Reynolds number hypersonic flows. Part II. The near wake of a blunt body at hypersonic speeds. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/XG0Q-ZA42. https://resolver.caltech.edu/CaltechETD:etd-12212005-083759 <https://resolver.caltech.edu/CaltechETD:etd-12212005-083759>

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Part I: Measurements were made of the heat loss and recovery temperature of a fine hot-wire at a nominal Mach number of 5.8. Data were obtained over an eight-fold range of Reynolds numbers in the transitional regime between continuum and free-molecule flow. At high Reynolds numbers, the heat transfer data agree well with the results of Laufer and McClellan, which were obtained at lower Mach numbers. At lower Reynolds numbers, the results indicate a monotonic transition between continuum and free molecule heat transfer laws. The slope of the heat transfer correlation also appears to vary monotonically, with Nu [...] at high Reynolds numbers and Nu ~ Re for Re< < 1. Data on the wire recovery temperature (corresponding to zero net heat transfer) were obtained for free-stream Knudsen numbers between 0.4 and 3.0. Comparison with previous supersonic data suggests that for Mach numbers greater than about two the normalized variation of recovery temperature in the transitional regime is a unique function of the free-stream Knudsen number. The recent data of Vrebalovich (33) suggests that the relation between the normalized recovery temperature and Knudsen number found in this investigation also applies to subsonic and transonic flow. The steady-state hot-wire may be used to obtain two thermodynamic measurements: the rate of heat transfer from the wire and the wire recovery temperature. An illustrative experiment was performed in the wake of a transverse cylinder, using both hot-wire and pressure instruments in a redundant system of measurements. It was shown that good accuracy may be obtained with a hot-wire even when the Reynolds number based on wire diameter is small. Part II: A theoretical model of the near wake is derived following the ideas of Chapman. This model is based on the postulates of mass conservation in the base flow region, thin viscous shear layers, and a recompression process which is independent of Reynolds number. The analysis, which includes the effects of initial shear layer thickness and base flow temperature, shows that the characteristics of the near wake (base pressure, shear layer angle, etc.) are independent of Reynolds number, and that the shear layer and initial wake thicknesses are proportional to Re[...]. A series of experiments are presented which show that the postulate of thin shear layers is invalid for Reynolds numbers less than about [...]. At higher Reynolds numbers, the theory is qualitatively incorrect if the Mach number [...] external to the shear layer is large. Detailed measurements with a steady-state hot-wire in the near wake of a two-dimensional circular cylinder indicate that the compression process at the neck is not isentropic, and that the maximum pressure rise occurs downstream of the stagnation point formed by the merging shear layers. Comparison between the experimental and theoretical results points out the importance of the base flow temperature and the initial shear layer profile in determining the observable characteristics of the near wake.