Modelling of Compressible Fluid Flow of Binary Gas Mixtures in Acoustic Resonance Systems Using OpenFOAM

In this work, the oscillatory flow of a homogeneous binary gas mixture was simulated in a computational domain consisting of a quarter-wavelength standing-wave acoustic resonator. The set of flow governing equations are the unsteady compressible Navier-Stokes equation, the unsteady continuity equation, the unsteady energy equation, and the state equation for ideal gases. Thermophysical properties of a Ar-Xe mixture were considered for the calculations of viscous and thermal acoustic attenuation effects in the boundary layer region. Simulations were carried out with the open-source CFD package OpenFOAM, using its standard solver for compressible unsteady flow rhoPimpleFoam. The standing-wave oscillatory flow was achieved by the implementation of a time-dependent sinusoidal pressure boundary condition, acting as the resonator's acoustic source. Simulation results have shown that pressure and velocity field values are in good agreement with the analytical approximations for an acoustic quarter wavelength resonance channel. Additionally, thermal effects on the boundary layer region are explained by analyzing the heat transfer process occurring within a whole acoustic cycle. This model methodology demonstrates that CFD analysis of flow and heat transport processes in acoustic systems can be used as a predictive tool of the performance of devices where thermal effects are important, and gas mixtures are generally used as the working fluid.