The Velocity Distribution at the Interface between Two Liquids

By carrying out detailed experiments in a water flume of dimensions 180 cm×50 cm×15 cm we have observed, by the use of a suitable colouring material, the velocity distribution near the interface between two superposed liquids having different densities, the lighter liquid flowing over the heavier one confined in a hollow. It has thus been found that if there is any difference, however small, between the densities of the two liquids, the velocity of the upper liquid decreases fairly rapidly near the interface, as if it were a solid plane, while the lower liquid is almost at rest in the hollow. Attempts have then been made to explain the observed flow pattern theoretically. First, a rather simple approximate calculation has been performed by assuming that the liquids are in direct contact with each other, but no satisfactory explanation of the observed flow pattern has been obtained. We have next carried out an improved calculation by assuming that there is formed a thin intermediate zone between the two liquids and it has been found that the calculation flow pattern is, in this case, in fairly good agreement with the observed one.