RADIATION DOMINANT INTERACTION IN GASDYNAMICS.
MASSACHUSETTS INST OF TECH CAMBRIDGE AEROPHYSICS LAB
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The problem of an interaction between a dominant radiation field and a flow field is investigated. It is shown that the time scale for such an unsteady interaction may be very short in comparison with a characteristic flow time. Consequently, to the lowest order, the physical picture is that of a radiative cooling process with the flow remaining unchanged. Expansion in powers of Boltzmann number is then possible to systematically include higher order effects. Results were obtained for a specific example consisting of an instantaneous addition of energy within a finite region of one-dimensional symmetry i.e. planar, cylindrical and spherical geometries. For simplicity the gas is assumed inviscid, perfect and in local thermodynamic equilibrium, and the radiation field is governed by the differential approximation version of the exact formulation. A numerical scheme was developed for treatment of the radiation field in order to avoid time-consuming iterations. Results indicate a negligible upstream heating level, moderate nongrey but large curvature and optical thickness effects. Depending on the local balance between emission and absorption, the shock wave can be either accelerated or decelerated. Comparison between the differential approximation and exact formulation for a planar, grey case is made. Excellent agreement between the present work and a laser experiment indicates the possible energy coupling inferred. Author
- Fluid Mechanics