TRANSIENT THERMAL-BLOOMING OF A VERTICAL LASER-BEAM

The thermal blooming regimes are identified and analysed for a vertica l laser beam under conditions of free convection in an absorbing mediu m. The characteristic times, velocities, scales of temperature changes , and scaling parameters are determined for all the regimes. The equat ions of conservation of the medium are obtained and solved numerically in the approximation of paraxial wave optics under strong and moderat e convection conditions. A comparison is made with the published exper imental results. The reason for the appearance of turbulence at low Re ynolds numbers is considered on the basis of these experimental result s.