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Drag and lift forces on a rotating sphere in a linear shear flow

Published online by Cambridge University Press:  10 April 1999

RYOICHI KUROSE  and
SATORU KOMORI
RYOICHI KUROSE
Affiliation:
Department of Mechanical Engineering, Kyoto University, Kyoto 606-8501, Japan Present address: Yokosuka Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), Yokosuka, Kanagawa 240-0196, Japan.
SATORU KOMORI
Affiliation:
Department of Mechanical Engineering, Kyoto University, Kyoto 606-8501, Japan
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Abstract

The drag and lift forces acting on a rotating rigid sphere in a homogeneous linear shear flow are numerically studied by means of a three-dimensional numerical simulation. The effects of both the fluid shear and rotational speed of the sphere on the drag and lift forces are estimated for particle Reynolds numbers of 1[les ]Rep[les ]500.

The results show that the drag forces both on a stationary sphere in a linear shear flow and on a rotating sphere in a uniform unsheared flow increase with increasing the fluid shear and rotational speed. The lift force on a stationary sphere in a linear shear flow acts from the low-fluid-velocity side to the high-fluid-velocity side for low particle Reynolds numbers of Rep<60, whereas it acts from the high-velocity side to the low-velocity side for high particle Reynolds numbers of Rep>60. The change of the direction of the lift force can be explained well by considering the contributions of pressure and viscous forces to the total lift in terms of flow separation. The predicted direction of the lift force for high particle Reynolds numbers is also examined through a visualization experiment of an iron particle falling in a linear shear flow of a glycerin solution. On the other hand, the lift force on a rotating sphere in a uniform unsheared flow acts in the same direction independent of particle Reynolds numbers. Approximate expressions for the drag and lift coefficients for a rotating sphere in a linear shear flow are proposed over the wide range of 1[les ]Rep[les ]500.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 384 , 10 April 1999 , pp. 183 - 206
Copyright
© 1999 Cambridge University Press

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