High power laser optical systems often require gas flow in the optical train to control effects such as thermal blooming. The gas flow itself is a source of optical degradation for the laser beam. A series of experimental investigations have been performed for scale simulations of a typical optical train. These included water table simulations for flow field visualization and a gas flow simulation for assessment of optical degradation. Optical and flow turbulence effects for the type of gas used and the method of flow injection have been ascertained. It was determined that substantial optical degradation can be caused by the flow and a number of qualitatively desirable flow implementations were identified.