Numerical study of 2D and 3D flowfields in a high‐power pulsed chemical laser

High‐power chemical lasers operating in high repetitive rate show a decrease of the output energy laser beam. In such lasers, the characteristic time which depends on the laser output is short in comparison with those related to the flow. Consequently, shock waves, acoustic waves and thermal perturbations, induced by the strong electric energy deposition and remaining in the laser cavity between two pulses, may explain the decrease of output energy of the laser beam. For a better understanding of the flowfields, a numerical approach is carried out using flux corrected transport algorithms (FCT methods) associated with a Riemann solver on the computational domain boundaries. Under two‐dimensional assumptions, the inviscid flow in the convergent‐divergent laser cavity is computed to describe the creation and propagation of the wave system and the hot gas column in both single and multidischarge operating modes. Distortions of the contact surfaces are put into evidence through the study of flowfield instabilities. Finally, the limitations of the two‐dimensional modelization become apparent. The numerical resolution is extended to a 3D case in order to take into account the optical direction. This allows to study the influence of shock waves travelling between optics and being generated by a side effect developing at the electrodes. These waves have an effect of long duration on the flowfield and lead to a high residual perturbation level.