3-DIMENSIONAL MODELING OF PROCESSES IN THE FAST-AXIAL-FLOW CO2-LASER

The previously developed three temperature approximation for the analy sis of the processes in the industrial fast-axial-flow CO2 laser is ap plied to the general three-dimensional (3D) modelling of the compressi ble flow in the laser cavity. The 3D geometrical representation and th e compressible flow formulation allowed us to describe the realistic f low pattern and the distribution of the laser parameters. Our model pr edicts the development of the velocity profile along the laser from on e which is near parabolic due to turbulent jet impingement, to one whi ch is representative of a turbulent pipe flow. The translational tempe rature, T, the vibrational temperature of the symmetric stretch mode O f CO2, T1, (almost equal to the vibrational temperature of the double degenerate bending mode of CO2, T2), the vibrational temperature of th e asymmetric stretch mode of CO2, T3, and the vibrational temperature of N2, T4, are shown to increase along the laser axis except under the inlet openings, with T reaching about 360 K, T1 almost-equal-to T2 re aching about 400 K, and T3 and T4 reaching about 3000 K. The values of T and flow velocities away from the inlet openings coincide within th e accuracy of about 10% to those predicted by the 2D model. The averag e values of T3 and T4 (about 2500 K) seem to be in better agreement wi th experimental observations than those predicted by the 2D model. The predicted population inversion reaches its maximum value of about 5 X 10(20) m-3 inside the recirculation zones between the inlet openings. We believe that our approach to the modelling of the processes in the CO2 laser may have a wide range of scientific and industrial applicat ions far beyond the particular type of laser discussed in this paper.