The influence of the optical window for output radiation on the flow characteristics insupersonic CO laser

A characteristic static pressure of active medium in supersonic CO-laser is 50 Torr. Lasers of this type have an optical window for output radiation, which divides the laser medium from outer atmosphere and is closed using a special optical material, or a gas-dynamic valve.

A typical flight height of an aircraft with an airborne laser is 10 km. At this height, the atmospheric pressure is sufficiently small (200-230 Torr) to use a laser, in which an optical window for output radiation does not require a special optical material, or a gas-dynamic valve to close it.

In practice, it is important to understand the effect of outboard airgetting into the gas-dynamic laser path through the optical resonator window on the gas-dynamic flow characteristics in the gas-discharge chamber and in the resonator region of CO-laser.

The paper presents simulation results for the basic gas-dynamic parameters of a steady gas flow in the gas-dynamic path of supersonic CO-laser with regard to an air flow through its optical window. The simulation was performed for optical windows of different structures.

Three modified structures of optical window are shown:

- air enters directly from atmosphere;

- air enters through a «comb»;

- «gas window» is used for ground starting.

2D simulations were carried out. The Navier-Stokes equation system was solved. A standard k-e model with the transport equations for kinetic energy of turbulent motion and its dissipation rate equations was used to calculate the turbulent Reynolds stresses.