Pressure Variation on a Flat Wall Induced by an Approaching Vortex Ring

Abstract

Variation of pressure was measured by using a condenser microphone, when a vortex ring was approaching a flat wall. Considerably large negative pressure was observed even at the stagnation point on the wall. This negative pressure was found to occur when the ring “rebounded” from the wall. Before the ring rebounding, the pressure variation could be predicted approximately by the potential flow theory. After the rebounding, it showed negative values, entirely different from the theory. However, this fact can be illustrated by the potential theory applied to a simple, modified model of trajectory of the ring during the rebounding, which takes account of the viscosity effect.