Modeling of Radiometric Force Actuation using the DSMC and ES/BGK Approaches

Radiometric Force Actuation (RFA) refers to a non-equilibrium phenomenon when a total force is exerted on an object submerged into a gas under the conditions of temperature inequality between the object and the gas container walls. The thermal stresses in the gas generate a flow which results in a force which has a maximum in rarefied regime. The flow is called ``radiometric'' because it is similar to the gas flow that rotates the vanes of Crookes' radiometer. This gas flow phenomenon combined with modern low heat-conductivity materials can be exploited to create microactuators driven by radiant or resistive heating. Two kinetic methods - the direct simulation Monte Carlo, a stochastic approach, and the discrete-ordinate solution of ES/BGK equation, a deterministic approach, are applied for analysis of the radiometric flow generated by an non-uniformly heated plate. The dependence of the radiometric force on the Knudsen number is examined as well as the effects of the non-uniform temperature distribution across the plate.