The profile of an oil-water interface in a spin-up rotating cylindrical vessel

The dynamics of a two-layered rotating liquid at low angular velocity in a cylindrical container is explored, both experimentally and theoretically, using an oil-water system. In the two-layered liquid, a transient concave down paraboloid interface, containing undulations, is observed before the final, stable concave up paraboloid interface develops. A simple yet effective model is developed to explain the observed profile dynamics, in which the predicted maximal height of the paraboloid agrees well with experimental measurements over a fairly large range of rotation speeds. (C) 2017 American Association of Physics Teachers.