FLSPRY, the Program for the Analysis of a Laser Beam Focused Within an Aerosol Spray (FLSPRY) was developed for theoretical analysis of the propagation of a laser pulse optically focused within an aerosol spray. FLSPRY can be applied, for example, to analyze laser ignition arrangements where a focused laser pulse would be used to ignite a liquid aerosol fuel spray. Laser light scattering and absorption of the individual aerosol droplets are evaluated using electromagnetic Lorenz-Mie theory. Initially, beam propagation is being modeled using a simple modified paraxial theory, which would limit applications to relatively "optically thin" sprays.
To keep from limiting the application of the program to "optically thin" sprays, a Monte Carlo analysis of the laser beam has been adapted to FLSPRY. The Monte Carlo analysis follows individual "light packets" through a dense spray of defined thickness and composition. The spray is assumed to be monodispersed and homogeneous, and the light packets enter along the same axis with perpendicular incidence. The Monte Carlo algorithm was modified to account for the spatial variation of intensity and the variable angle of incidence at the illuminated side of the spray. An appropriately weighted Monte Carlo decision is used to determine the position of incidence for each light packet. After a large number of attempts, a Gaussian intensity profile will be generated.
Input parameters to FLSPRY include the liquid volume fraction, average droplet size, droplet size distribution, laser wavelength, laser pulse energy, laser pulse duration, lens focal length, beam diameter incident on the lens, and the choice of aerosol liquid and surrounding gaseous medium. Other inputs include Monte Carlo analysis indicator, radius (cm) for Monte Carlo analysis, location of Monte Carlo analysis (cm) relative to the lens, number of Monte Carlo attempts, and random number generator seed for Monte Carlo analysis. Also necessary for Monte Carlo analysis are the xmax, xmin, ymax, and ymin thicknesses of the spray (cm). The output of the computer program includes, as a function of spatial position along the laser propagation axis within the spray, the laser pulse intensity and energy, the overall volumetric absorption of laser energy by the aerosol liquid and by the gaseous medium, and the overall average temperature rise of the aerosol liquid and of the gaseous medium.
FLYSPRY carries the NASA case number LEW-16065. It was originally released as part of the COSMIC collection.