Numerical study on the influence of Helmholtz resonators on gas mixing performance

Helmholtz Resonators are extensively used in various engineering applications to control acoustic phenomena, but their impact on gas mixing has not been studied yet. In this research, numerical flow simulations within a channel in the presence of Helmholtz resonators were conducted to model the gas mixing process inside the channel and investigate the effect of increasing the number of resonators on the mixing process. The Fluent 2022R2 was utilized for solving the unsteady Reynolds-averaged Navier-Stokes equations. The fluid was considered compressible, and the K‒ε turbulence model was used to model turbulence. To validate the numerical results, a test rig was prepared to measure the frequency and pressure oscillation amplitude inside the resonator, and the numerical results were compared with the experimental results. The numerical results revealed the significant role of Helmholtz resonators in enhancing gas mixing. Vortex shedding at the cavity edge and generating positive and negative pressure waves in opposite cavities led to oscillatory flow in the channel and the mixing of two gases. Increasing the resonators to three pairs resulted in even greater gas mixing enhancement so that the difference between the maximum and minimum temperatures of the two gases at the outlet decreased by 87% compared to that at the inlet. These findings provide deeper insights into the underlying mechanisms on gas mixing and offer insights for designing and optimizing mixing systems in various industrial processes.