Motion Of Rarefied Gas Research Articles

Effects of Soft Interaction and Non-isothermal Boundary Upon Long-Time Dynamics of Rarefied Gas

In the paper, assuming that the motion of rarefied gases in a bounded domain is governed by the angular cutoff Boltzmann equation with diffuse reflection boundary, we study the effects of both soft intermolecular interaction and non-isothermal wall temperature upon the long-time dynamics of solutions to the corresponding initial boundary value problem. Specifically, we are devoted to proving the existence and dynamical stability of stationary solutions whenever the boundary temperature has suitably small variations around a positive constant. For the proof of existence, we introduce a new mild formulation of solutions to the steady boundary-value problem along the speeded backward bicharacteristic, and develop the uniform estimates on approximate solutions in both \(L^2\) and \(L^\infty \). Such mild formulation proves to be useful for treating the steady problem with soft potentials even over unbounded domains. In showing the dynamical stability, a new point is that we can obtain the sub-exponential time-decay rate in \(L^\infty \) without losing any velocity weight, which is actually quite different from the classical results, such as those in Caflisch (Commun Math Phys 74:97–109, 1980) and Strain and Guo (Arch Ration Mech Anal 187:287–339, 2008), for the torus domain and essentially due to the diffuse reflection boundary and the boundedness of the domain.

Effects of carbon fiber gas pressure, temperature and deposition distance on thermo fluids phenomena in vacuum deposition machine

A numerical analysis method (DSMC, Direct Simulation Monte Carlo)[1] was developed to simulate the molecular motion of rarefied gases. In the present paper, numerical approaches by the DSMC method have been carried out. By the computation model of CC-40F carbon coater, the cylindrical deposition machine has axial symmetry; the flows inside the vacuum chamber were analyzed. The substrates were put on the bottom and the fiber near the ceiling in the computational domain. In the computational model, air and carbon molecules are working ones. The effects of the air gas pressure variation in the chamber, the effects of the deposition distance variation and the surface temperature variation of the carbon fiber on thermo fluids phenomena are discussed and visualized. Changing the number density of carbon and air, the temperature of the carbon and the velocity of the carbon in the chamber are discussed. With changing the surface temperature of the carbon fiber, qualitative assay of experiment and simulation result is in similar trend very well. The DSMC method is a forceful tool for the study of rarefied gas flow in vacuum deposition machine.