Investigating fluid dynamics via gas diffusion using Bout++ fluid simulation*

Investigating gas diffusion is crucial to the understanding of fluid dynamics via particle diffusion. The diffusion is realized whenever there exists a gradient in Gibbs free energy or chemical potential of the fluid. In order to study such a dynamics, we simulate gas diffusion utilizing fluid simulation via BOUT++ by developing a mesh generator, and compiling a series of challenging test problems for diffusion codes in addition to a basic neutral fluid model. The gas diffusion fluid equations in one-dimension as well as in two-dimensions are solved with and without convective terms. This shows a significant impact of the convective term in the process of diffusion for different kinds of gases having different diffusion coefficients. The further insight is drawn through different fluid properties by changing the initial density profile of the gases. Starting from the very basic density profile as the Gaussian profile, we develop results by introducing the density gradient in the profile via changing the rising and fall times, and broadening of the peak region. A quick diffusion is obtained for the case of fluid having larger density gradient. The results could be important for the transport and turbulence in various kinds of fluids.