Investigation of Gas Diffusion by using Bout++ Fluid Simulation: Role of Density Gradient

Abstract

The present work simulate gas diffusion by fluid simulation and examine 1-D situation using BOUT++. We have extended the BOUT++ code to solve the gas diffusion fluid equations, added a simple neutral fluid model, created a mesh generator, and collected a set of complex test problems for diffusion codes. Progressing stepwise, firstly, the gas diffusion equation in 1-D,  2-D, and 3-D has been solved with the help of simulation and then added the convective term to the diffusion equation for its solution. The simulations showed that the convective term has a significant effect on the process of diffusion. Also, the diffusion coefficient that depends on the type of gas shows its influence on the diffusion process. For uncovering the role of density gradient, the initial density profile is taken to be Gaussian and then the results are compared with the case of superGaussian density profile. In the case of super-Gaussian density profile, the gas diffusion takes place at a much faster rate. The study puts a light on the basic diffusion process, playing role in the concept of particle acceleration and the study of Tokamaks for its application in nuclear fusion.