The expression of the force acting on a sphere in unsteady motion is known nowadays, for Reynolds numbers ranging from 0.1 to 300. For large Reynolds numbers it is assumed that this force is equivalent to stationary drag. This work is about to the experimental determination of the usually neglected forces. This study is performed on golf balls, in the range of Reynolds between 50000 and 250000. For this, accelerated and decelerated flows are made in a wind tunnel with a variable force measuring device. The experimental results confirm the hypotheses that the inertia forces due to the displacement of the mass of the fluid and the forces due to the history of the movement are negligible in supercritical regime; which is not the case in critical regime. Furthermore non-dimensional parameters of this force have been determined.
展开▼
