Journal of Fluid Mechanics

Drag on a sphere moving horizontally in a stratified fluid

a1 Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW, UK


The steady translational motion of a sphere in a Boussinesq stratified fluid, where the motion is parallel to the stratification surfaces, is studied. A model based on existing linear gravity wave theory for large Froude numbers and on new theory for small Froude numbers is presented. The small-Froude-number theory describes wave generation and the presence of a rectangular-section attached wake whose size and shape is controlled by the size and shape of the wave generation regions. Existing laboratory data are used to evaluate the model's prediction for the drag coefficient of the sphere as a function of Froude number.

(Received September 6 1999)
(Revised May 24 2000)