To excite optical vortices using high-power millimeter waves, we use a miter bend with a spiral phase mirror. Through numerical simulations, we demonstrate that vortex beams can be successfully excited by employing a spiral phase mirror that appropriately accounts for the phase difference between the input and output modes. The simulations also reveal the generation of higher-order modes caused by diffraction inherent to the miter bend structure and unintended reflections arising from the singularity at the optical axis of the spiral phase mirror. Additionally, we propose a method to estimate the topological charge, which corresponds to the vorticity, from real-valued data. The simulation results confirm that vortex beams are successfully excited as the dominant mode.

This study investigates the prediction accuracy of the Smagorinsky model in low Reynolds number periodic unsteady anisotropic turbulence. This model is required to decrease the value of the model constant with decreasing Reynolds number under low Reynolds number conditions, as seen in wall turbulence. The turbulent kinetic energy results predicted using the Smagorinsky model obtained in this study are compared with those obtained using the Vreman and coherent structure models. A large-eddy simulation based on the fourth-order central difference method is used in this study. Here, the model constants of each model are calibrated using turbulent fields under a high Reynolds number condition. Values of turbulent kinetic energy are presented by using not only time series results but also periodic averaged results. For the turbulence fields analysed in this study, the results obtained from the Smagorinsky model predictions agree with those obtained from the Vreman and coherent structure models under the low Reynolds number conditions.