VISUAL STUDY OF UNSTEADY FLOW PAST AN UNCONSTRAINED SPHERE RESTING ON A HORIZONTAL PLANE

摘要

A one-cycle, unidirectional, unsteady water flow with trapezoidal velocity profile takes place over an unconstrained sphere kept on a horizontal tangent plane. Experiments are done with steel ball, acrylic solid sphere and table tennis ball. The motion of the sphere and the flow features developing around the sphere are studied. Each sphere presents a typical case in itself: (i) the steel ball remains stationary, (ii) the acrylic solid sphere moves, and (iii) the table tennis ball moves faster than the flow. Wake profiles for each of these spheres differ, and they are discussed here.