Influence of air-water interface condition on rotating flow stability : experimental and numerical exploration

Overview & Synopsis

Our study focuses on the first instability that appears in a flow generated by a rotating disc placed at the bottom of a fixed cylindrical cavity, with a flat liquid-gas interface. Owing to the dual numerical and experimental approach, we highlight a robust mismatch on the threshold of this instability. After having assumed and later ruled out that mechanical vibrations could be responsible for these mismatches, this investigation has focused on the boundary condition used in simulations at the interface air-water and its influence on the flow. We show that the free slip condition does not allow to simulate the same flow as in the experiments. Several models of this interface are explored in order to reduce the mismatches. In particular, taking into account variations in surface tension depending on the concentration of a pollutant at the interface results in a considerable reduction of the error on the critical Reynolds number, and to a more accurate reproduction of the flow in the simulations.