HF chemical laser amplification properties of a uniform, turbulent mixing layer

Abstract

The laser amplification properties of a turbulent chemically reacting stream consisting of hydrogen, fluorine, and the first four vibrational levels of the HF molecules are analyzed. In order not to add to the complexity of the problem, a simple flow configuration consisting of the turbulent mixing layer of uniform mean velocity is considered. The analysis is carried out by the use of the turbulent flow theory developed earlier by one of the present authors. It is shown that this theory can be successfully employed to analyze the complicated chemically reacting flow problems which are coupled with the laser radiation field. The governing equations are hyperbolic and, therefore, the method of characteristics is employed for the solution. Various sums of the chemical and thermal energies and the mass shared among the reaction partners are found to be the properties which propagate along two of the three characteristics. These are invariants except for the dissipative process and the chemical and radiative reactions. Mean laser gain coefficients as well as the other mean quantities pertinent to the amplification properties are evaluated for the infinitely fast pumping reactions and for the finite collisional and radiative deactivation rates. The turbulence is found to affect the laser performance mostly through its effect on the pumping reaction rates which are governed by the turbulent dissipation rate.