81 / 2019-09-30 16:10:28

DSMC Simulation of Periodically Patterned Radiometric Pumps

Direct Simulation Monte Carlo, Rarefied Gas, Numerical Simulation.

With the aid of direct simulation Monte Carlo (DSMC), a detailed investigation is reported considering the fluid and thermal characteristics of rarefied gas flow with regard to various arrangements for radiometric pumps featuring vane and ratchet structures. For the same, we consider three geometries of radiometric pumps consisting of channels with their bottom or top surfaces periodically patterned with different structures. The structures in the design of the first geometry are assumed to be on the bottom wall and consist of a simple vane. The second and third geometries contain either a channel with double isosceles triangular fins on its lowermost surface or a zigzag channel with double isosceles triangular fins on both walls. The temperature is kept steady on the horizontal walls of the channel; thus, radiometric flow is produced by subjecting the adjacent sides of the vane/ratchet to constant but unequal temperatures. The DSMC simulations are performed at a Knudsen number based on the vane/ratchet height of around one. The dominant mechanism in the production of radiometric force is clarified for the examined configurations. Our results demonstrate that at the investigated Knudsen number the zigzag channel experiences maximum induced velocity with a parabolic velocity profile, whereas its net radiometric force vanishes. In the case of all other configurations, the flow pattern resembles a Couette flow in the open section of the channel situated above the vane/ratchet. For binary mixtures, we demonstrate that the arrangement with the double isosceles teeth embedded just on the bottom wall performs a measurable gas separation with a linear species variation along the pump height.