Investigation of Transition Within the Channels of a Gas-Cooled Laser Amplifier Head Using RANS Simulations*

In an effort to improve the thermal management of high-average power, high-intensity lasers, this study focuses on simulating the gas flow through multiple thin channels. In particular, the current approach for cooling such laser systems makes use of passing helium gas through an array of closely-spaced, thin vanes, where each vane contains a thin slab of gain medium. Since the role of turbulence is crucial to both the thermal management of the gain material and to the optical quality of the laser, it is imperative that the state of the flow within these channels is properly understood. In the absence of experimental data, the current work utilizes RANS turbulence and transition models to obtain flow solutions. Initial results indicate that the flow remains laminar further downstream than expected, and beyond typical critical Reynolds numbers. With this in mind, special emphasis is placed on studying flow features relating to relaminarization, where comparisons are made with classical transition metrics of boundary layers. Results of this study, in addition to the possibility of comparisons to experimental and LES data, give insight into the direction for optimal thermal management of similarly designed gas-cooled laser systems.