

Article
Force on a spinning sphere moving in a rarefied gas
Authors: 
Borg, K., Söderholm, L. H. S., Essén, H. 
Document Type: 
Article 
Pubstate: 
Published 
Journal: 
Phys. Fluids 
Volume: 
15
73641 
Year: 
2003 
AbstractWe calculate the force acting on a spinning sphere moving in a rarefied gas. It is found to have one transversal contribution of opposite direction compared to the socalled Magnus force normally exerted on a sphere by a dense gas. It is given by \[\vecF=\alpha_\xi \frac\pi R^3\rho\,\vecomega\times\vecv,\] where $\alpha_$ is the accommodation coefficient of tangential momentum, $R$ the radius, and $\rho$ the density of the surrounding gas. $\vecomega$ is the angular velocity and $\vecv$ is the velocity of the center of the sphere relative to the gas. The dimensionless factor $\xi$ is close to unity, but depends on $\omega$ and $\kappa$, the heat conductivity of the body. One contribution is found to be a correction to the linear damping force. Another is a force that is parallel to $\vecomega$.

