Weakly compressible fluid model to study thermal effects on laser propagating in closed tube

The iso-pressure approximation model used in laser propagation in gas medium and its disadvantage under complex border conditions were analyzed. The weakly compressible fluid model based on the Mach uniform method introduced by Peter Wesseling was developed. Using the weakly compressible fluid model and scalar wave equation, a numerical study was carried out for the gas thermal effects on laser propagating in a closed tube full-filled with air. The far-field beam shape at different time were obtained and compared with the experimental ones. The weakly compressible fluid model could be well adapted problems with complex border conditions, which proves that it is more flexible than the compressible fluid model or the iso-pressure approximate model．