The fluid dynamics of continuous wave chemical lasers

The extremely complex species mixing phenomena that occur in flowing, continuous wave, chemical lasers have been investigated using a computer model. The model calculates the dynamics of the various species coupled with finite rate chemical reactions. Studies have been made of several laser designs in which fluorine is admitted into the laser cavity through an array of supersonic nozzles where it mixes and reacts with hydrogen entering from separate orifices. The chemical reactions produce HF in excited vibrational states and release significant amounts of heat. Of particular interest are the effects on mixing of lateral pressure gradients that result from the heat release and the presence of embedded shocks in the flow. The numerical procedure uses finite difference approximations to the full time-dependent Navier-Stokes equations in two space dimensions together with species transport equations and chemical kinetics. Comparisons between the calculational results and chemiluminescence photographs of the flow field show excellent agreement for the spatial distribution of HF in the cavity. The results help to explain experimental observations and suggest new directions for achieving optimum laser efficiency.