Rotation Driven Entrainment of Air inside Liquids: An Experimental Study
Understanding the behavior of fluid when particular external field is applied to it, is one of the most interesting works pursued in fluid mechanics. In this paper, following the same trend, we have presented our quantitative study of entrainment phenomenon caused by submerged rotary field. Cylindrical disk placed horizontally in water and rotated around its vertical axis to generate a trough at the center of free surface. Numerous experiments have been performed in order to determine the characteristics of entrainment and understand the effect of parametric variation over it. Starting from flat interface it results certain apparently steady interfacial profile. Higher rotational inertia and lesser submergence of field favors the phenomenon of air entrainment. The temporal evolution of entrainment reveals pointed curvature like cusped singularities in its profile during the initial stages. The presence of entrained air filaments in the high inertial zone near the disk periphery leads to radial growth of entrainment, along with its downward motion driven by centrifugal effect of the surrounding liquid. The balance of viscous resistance and inertia is also controlled by the initial submergence of the rotating disk along with its rotations. Outcomes of the present study can be utilized for the mechanism design of chemical reactors, stirring processes and devices relating interfacial transfer process as a working principle.