Journal of Fluid Mechanics

Papers

Origins of radiometric forces on a circular vane with a temperature gradient

NATHANIEL SELDENa1, CEDRICK NGALANDEa1, NATALIA GIMELSHEINa2, SERGEY GIMELSHEINa2 c1 and ANDREW KETSDEVERa3

a1 University of Southern California, Los Angeles, CA 90089, USA

a2 ERC Incorporated, Edwards AFB, CA 93528, USA

a3 University of Colorado at Colorado Springs, Colorado Springs, CO 80933, USA

Abstract

Radiometric force on a 0.12 m circular vane is studied experimentally and numerically over a wide range of pressures that cover the flow regimes from near free molecular to near continuum. In the experiment, the vane is resistively heated to about 419 K on one side and 394 K on the other side, and immersed in a rarefied argon gas. The radiometric force is then measured on a nano-Newton thrust stand in a 3 m vacuum chamber and compared with the present numerical predictions and analytical predictions proposed by various authors. The computational modelling is conducted with a kinetic approach based on the solution of ellipsoidal statistical Bhatnagar–Gross–Krook (ES-BGK) equation. Numerical modelling showed the importance of regions with elevated pressure observed near the edges of the vane for the radiometric force production. A simple empirical expression is proposed for the radiometric force as a function of pressure that is found to be in good agreement with the experimental data. The shear force on the lateral side of the vane was found to decrease the total radiometric force.

(Received March 24 2009)

(Revised April 30 2009)

Correspondence:

c1 Email address for correspondence: gimelshe@usc.edu

Metrics