Exchange flows in rotating pipes*

In this work, the effects of a pipe axial rotating motion on buoyant miscible flows in inclined pipes are studied via experimental methods. The experiments are carried out in a long transparent pipe with closed ends and an automated gate valve making a lock-exchange flow configuration. A system of a stepper motor is employed in order to generate a stable and precise axial rotation speed.  The experiments are recorded using a high-speed digital camera to visualize flow patterns in the pipe. The analysis of our experimental results reveals how the interpenetration of the light and heavy fluids are affected by changing the experimental parameters, such as the pipe inclination angle, density difference, viscosity and pipe rotation speed. In particular, the results show in detail how the interpenetration front velocities vary with the pipe rotation speed. The results are quantitatively analyzed using the flow dimensionless groups, such as the Rossby number, and the characteristic velocities that describe the flow dynamics.