Flow Behavior in a Curved Converging Diverging Duct Employed in a Dye Laser

Abstract

In this paper the flow behavior in a converging diverging curve duct used in a high stability dye laser pumped by Copper Vapour Laser(CVL) is presented at different angular positions. The flow duct is formed by two eccentric cylinders of finite height. The channel aspect ratio and effective curvature ratio varies from 1 to 50, and 1 to 81, respectively, along the flow path. The flow behaviors at different sections of test duct are studied numerically and experimentally using a dye solvent mixture of 70 % glycol and 30 % ethanol. It is shown that the average values and variation of eddy sizes gradually reduces along the flow path till CVL pump position and then gradually increases. A non linear CFD turbulence model is used to get enhanced numerical results for accelerating curved flow. The numerically estimated average values of turbulent kinetic energy and its dissipation rate at different angular positions are compared with the intensity variation of He Ne laser passing through the flow. The flow field tends to become more stable at higher Reynolds number and at lowest hydraulic diameter (CVL pump position). The average variation of flow and temperature inhomogeneities in boundary layer at CVL pump position reduces with the increase in flow rate. The variation in dye laser band width and wave length is correlated with flow and temperature induced inhomogeneities for different flow speed.