TURBULENT MIXING IN THE BASE FLOW REGION
XEROX ELECTRO-OPTICAL SYSTEMS PASADENA CA
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An exploratory study is made in connection with the problem of predicting properties of the turbulent base flow region of a body at hypersonic speeds. An attempt is made to calculate the gross features of the base flow using a non-similar mixing model including the ChapmanKorst recompression condition. The expression for the eddy viscosity is based on a model which allows the turbulent equations to be transformed into incompressible laminar form. The empirical factor in the eddy viscosity expression is evaluated from data obtained from the near field in the linear growth region of jets exhausting into a quiescent region. The same expression for the eddy viscosity is then used in an attempt to estimate the growth of non-similar turbulent mixing layer using both turbulent and laminar initial profiles. The correlation of turbulent jet mixing data for speeds up to Mach 3 shows that the eddy viscosity is a very strong function of Mach number or of density ratio across the jet, since the data are for adiabatic flow. If the eddy viscosity dependence on density ratio persists for density ratios typical of re-entry conditions, then it is found that at these conditions the growth rate of the turbulent shear layer is orders of magnitude slower approaching the rate of growth of the laminar mixing layer under the same conditions.
- Fluid Mechanics