GENETIC ALGORITHM APPROACH AND EXPERIMENTAL CONFIRMATION OF A LASER-BASED DIAGNOSTIC TECHNIQUE FOR THE LOCAL THERMAL TURBULENCE IN A HOT WIND TUNNEL JET

This paper is devoted to a laser-based diagnostic technique described as a method for solving an applied inverse problem in turbulent media using laser beam propagation. This problem consists of extracting local information about temperature ∞uctuations inside a hot turbulent jet of air, from the luminous photodiode trace produced by a laser beam, after having traversed the jet. A genetic algorithm is implemented in order to calculate the optimized laser beam directions corresponding to the whole luminous trace. An approximated ray equation which is proved from the geometrical optics is solved numerically by using those directions and enables to determine the variance of temperature ∞uctuations along the whole path of the laser beam. A good agreement coming from the comparison between the results obtained and the published experimental data proves the validity of the method.