E. Radiative Control of Flow Problems in Aerodynamics

Abstract

Thomas:In the preceding four sessions, we have considered the aerodynamic flow problems involved in the pulsating variable stars. We have been particularly interested in the question of radiative control of the flow through radiative control of the internal energy state of the gas. If I abstract the overall discussion thus far, especially the contributions of Whitney and Oke, the argument is that the state of at least the observable regions of the atmosphere is the same as it would be if those regions belonged to a nonpulsating star having the same radiative flux and effective gravity. That is, in the pulsating star, the energy transfer situation finds at each phase some radiative flux, the manner of whose production is irrelevant for the present argument, but to which the internal energy state of the atmosphere adjusts in a time short compared with any time-variation of the flux or the flow-pattern relaxation time. Then, except for the pattern of spectral line-displacements accompanying the motion, the observed spectrum is fixed by this internal energy, which is fixed by the radiative flux. The dynamical effects of the pulsation fix the effective gravity. There is possibly a perturbation on this simple picture in the atmospheric regions where the shock happens to be; and Kraft suggests that in the outer atmospheric regions the variable and non-variable star differ because of the direct and indirect effects of an increased ‘turbulence’ generated by the pulsation.