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Forma, Vol. 25 (No. 1), pp. 15-22, 2010

Onset and Growth of Sand Ripples due to a Steady Viscous Flow in an Annular Channel

Yuki Oshiro and Osamu Sano*

Department of Applied Physics, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
*E-mail address: sano@cc.tuat.ac.jp

(Received May 10, 2010; Accepted July 12, 2010)

Abstract. A layer of glass beads of initially constant thickness confined in an annular channel was exposed to a viscous flow generated by the steady rotation of the upper annular plate. The critical velocity on the formation of ripples and the growth process were elucidated experimentally. Theoretical models were proposed to explain the initial stage of a ripple that reflects three-dimensional growth, the intermediate stage in which the growth of a ripple in the lateral direction is restricted by the side boundary, and the final stages of the ripples in which interaction of neighboring ripples maintain a stationary state.

Keywords: Sand Ripple, Viscous Fluid, Critical Velocity, Fourier Mode, Growth Model


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