Mesoscale Hydrodynamic Fluctuations in Nonequilibrium Gas Mixtures Across a Transpiration Membrane

Various separation technologies involve the transport of gas mixtures across species-selective membranes. At mesoscopic length scales, where the gas mean free path is much larger than the membrane pore size, the long-ranged hydrodynamical fluctuations that are thermally intrinsic in the transporting gas can get significantly modified. In this talk, I will describe our investigations into the spatial structure of hydrodynamical fluctuations in gas mixtures that are driven by concentration gradients across a transpiration membrane. To simulate thermal fluctuations in mesoscale gas mixtures, we utilize a fluctuating hydrodynamics framework, which extends the deterministic compressible Navier-Stokes equations by incorporating stochastic fluxes. The transpiration membrane is modeled using a Langevin equation implementation of the fluxes crossing the interface with a given transmission probability. The role of species-dependent transmission probability and concentration gradient on non-equilibrium hydrodynamical fluctuations will be described.