Estimation of Thermophoresis Acting on a Particle in Rarefied Gas by Use of DSMC Method. 2nd Report. Effect of the Position and Thermal Conductivity of the Particle in a Finite Space.

Abstract

Thermophoretic force acting on a particle in a finite space is numerically estimated from the point of view of the position and thermal conductivity of the particle. Simulations are performed by Direct Simulation Monte Carlo Method in which the force is calculated from momentum transports of molecules on the particle surface provided that particle Knudsen number is in the free-molecule region. It is confirmed that the thermophoretic force becomes higher toward lower temperature region in the intermediate region of space Knudsen number 0.01<KnH<10. The profiles of the force are nonlinear in the slip region 0.01<KnHl0.1but are linear in the transition region 0.1<KnHl10. The force gradient becomes small as KnH increases and the force is almost constant in the free-molecule region. The effect of the particle conductivity on the force becomes larger as KnHincreases but the effect is very small compared with a radiation effect.