Transient thermal blooming of a vertical laser beam

The thermal blooming regimes are identified and analysed for a vertical laser beam under conditions of free convection in an absorbing medium. The characteristic times, velocities, scales of temperature changes, and scaling parameters are determined for all the regimes. The equations of conservation of the medium are obtained and solved numerically in the approximation of paraxial wave optics under strong and moderate convection conditions. A comparison is made with the published experimental results. The reason for the appearance of turbulence at low Reynolds numbers is considered on the basis of these experimental results.