The motion induced by gravity of solid spheres in a vessel filled with fluid has been investigated experimentally at Reynolds numbers in the range from 1-74 and Stokes numbers ranging from 0.2-17. Trajectories of the spheres have been measured with a focus on start-up behavior, and on impact with a horizontal wall. Two models have been investigated. The first describes the accelerating motion of the sphere. The second model predicts the distance from the wall at which the sphere starts decelerating.
The flow in the vicinity of the sphere was measured by means of PIV. The time scales and flow structures strongly depend on the Reynolds number. Measurements performed are in good agreement with simulations performed at the Kramers Laboratorium.