CONTACT TIME DURING IMPACT OF A SPHERICAL-PARTICLE AGAINST A PLANE GAS-LIQUID INTERFACE - EXPERIMENT

The impact interaction of a solid sphere against an initially plane ga s-liquid interface is experimentally studied with a new experimental p rinciple. The interface is formed at the bottom of a capillary of abou t 8 mm inner diameter. The sphere impacts the interface inside the cap illary. The new principle is based on video imaging of the grey levels of the gas-liquid interface using light beam reflection. The grey lev els are recorded by a CCD high-speed video system. Collision time is d etermined as the time between the first two maxima of the grey levels and obtained by means of Fourier analysis. The dependence of collision time on the diameter and density of impacting particles is investigat ed and compared with the available theoretical models. The experimenta lly determined collision time is longer than the collision time predic ted by the available theories. The reasons for this disagreement are d iscussed. The disagreement may be affected by the dependence of the re storing force on the radius of the plane gas-liquid interface.