LIFT COEFFICIENT OF A STATIONARY SPHERE IN GRADIENT FLOW

This paper deals with the lift force on a stationary sphere close to a nd away from the boundary and supplements an earlier paper which dealt with the study of the drag force. The experimental setup, instrumenta tion, nature of boundaries, sizes of test sphere. ranges of Reynolds n umber and relative size of the sphere are all common to both the studi es. In this study, the time-averaged lift coefficient, like the drag c oefficient, is found to be a function of both the Reynolds number and the relative size. In view of the prevailing controversy concerning th e direction of lift force, a criterion has been evolved for the revers al of lift force in terms of Reynolds number and relative size.