2013/09/25 by Henri Lhuissier, Yoshiyuki Tagawa, Tuan Tran +1 · 3 citations
Engineering · #Fluid Dynamics and Thin Films #Fluid Dynamics and Heat Transfer #Nanomaterials and Printing Technologies
paper · doi:10.1017/jfm.2013.470
Abstract We investigate the levitation of a drop gently deposited onto the inner wall of a rotating hollow cylinder. For a sufficiently large velocity of the wall, the drop steadily levitates over a thin air film and reaches a stable angular position in the cylinder, where the drag and lift balance the weight of the drop. Interferometric measurements yield the three-dimensional (3D) air film thickness under the drop and reveal the asymmetry of the profile along the direction of the wall motion. A two-dimensional (2D) model is presented which explains the levitation mechanism, captures the main characteristics of the air film shape and predicts two asymptotic regimes for the film thickness h0 : for large drops h0 ∼ Ca2/ 3 κ b- 1 , as in the Bretherton problem, where Ca is the capillary number based on the air viscosity and κ b is the curvature at the bottom of the drop; for small drops h0 ∼ Ca4/ 5 (aκ b )4/ 5 κ b- 1 , where a is the capillary length.