Influence of Molecular Effects on the Emission of Sound in a Low-Velocity Impact of a Drop on Water Surface

Abstract

The dynamics of an impact pressure pulse and the evolution of the coalescence bridge between a drop and the surface of water are investigated in experiments on the impact of the drop on water surface in the range of low impact velocities U. Experimental sequences of radii r_i of the bridge, which are approximated by a function of the form t^1/2, are extrapolated to the instant of contact and are compared with radii r_k of the outer contour of the cross section formed by the bottom part of the drop with the surface. The impact pressure pulse exhibits the critical dependence on ratio \({\varepsilon _{\text{i}}}(U) = {\dot r_i}/{\dot r_k}\) of the velocities of spreading. The value of ε = 1 determines the velocity threshold below (above) which the pressure is hydrodynamic (hydroacoustic) by nature.