Shear layer control in a free-vortex aerodynamic window

摘要

A boundary-controlled aerodynamic window positioned adjacent the exit aperture of a gas laser is transparent to the laser beam emitted from the cavity of the laser. The boundary-controlled aerodynamic window is formed by a high velocity gas flow directed by a duct across the exit aperture for the laser beam isolating the low pressure region of the cavity from the high pressure of the atmosphere. The exit aperture is enlarged and an auxiliary gas flow injected along the sidewall of the duct adjacent the exit aperture to expand the thickness of the boundary layer. In a second embodiment, particulate matter is fixedly attached to the sidewall of the duct to increase the roughness of the wall surface. A third embodiment uses a plurality of nozzles, each injecting gas with a predetermined velocity.