EXPERIMENTS ON THE LIFT OF A SPINNING SPHERE IN A RANGE OF INTERMEDIATE REYNOLDS-NUMBERS

The lift force experienced by a spinning sphere moving in a viscous fl uid, with constant linear and angular velocities, is measured by means of a trajectographic technique. Measurements are performed in the ran ge of dimensionless angular velocities gamma = a omega/V lying between 1 and 6, and in the range of Reynolds numbers Re = 2aV/nu lying betwe en 10 and 140 (a sphere radius, omega angular velocity, V relative vel ocity of the sphere centre, nu fluid kinematic viscosity). A notable d eparture from the theoretical relationship at low Reynolds number, C-L =2 gamma, is obtained, the ratio C-L/gamma being found to significantl y decrease with increasing gamma and increasing Re. The following corr elation is finally proposed to estimate the hit coefficient in the ran ge 10 < Re < 140: C-L congruent to 0.45 + (2 gamma - 0.45) exp (-0.075 gamma(0.4)Re(0.7)).