Effects of vibrational relaxation of multi-atomic molecules on stagnation heat transfer

Abstract

The flow and temperature fields of multi-atomic gas near the stagnation of a cylinder are theoretically studied, taking molecular vibrational relaxation into account, and putting importance on heat transfer performances. Based on the continuum equations, the velocity and temperature jumps of translational, rotational and vibrational degrees are considered as the boundary conditions and effects of the vibrational relaxation for subsonic flow are discussed. The total heat transferred to the surface is the sum of heats due to the translational-rotational temperature and the vibrational temperature. The ratio of the heats depends much on the ratio of the flow characteristic time to the relaxation time of molecule, and consequently the total heat is much influenced by this ratio of the characteristic times. The effect of the flow-relaxation time on heat transfer is more remarkable in the vibrational nonequilibrium than in the thermal equilibrium main flow. Even in a continuum flow of Knudsen number of about 10 −4, the effect of vibrational relaxation on stagnation heat transfer is still appreciable.