Principal Investigator John Bush
Some topics under study include:
(*) Mixing by Bubbles -- A circular cap bubble rising through a fluid-fluid interface in a narrow channel of thickness 2.5 mm and width 40 cm. The lower milk-water solution is drawn up in the wake of the bubble and in the filament trailing the bubble. Bush & Eames (1998) characterize the transport properties of individual bubbles experimentally and theoretically.
(*) Drop Motion in Rotating Fluids -- Studies illustrate silicone drops rising slowly along the rotation axis of a rapidly rotating tank of water rotating at 60 rpm. Note the blocked regions, or 'Taylor columns' accompanying the drop motion. A theoretical and experimental study of axial drop motion in rapidly rotating fluids is presented in Bush, Stone & Bloxham (1995).
(*) Bubble Motion in a Thin Gap -- The anomalous wake accompanying a penny-shaped air bubble of diameter 8 cm rising through a thin gap of water bound between glass plates inclined at 3 degrees relative to the horizontal.
(*) Drainage of Soap Films -- A vertical soap film supported on a rectangular wire frame of height 3.5 cm and width 15 cm drains under the influence of gravity in an unsaturated environment. Evaporation at the top of the film disrupts the film shape, giving rise to a horizontal bump which grows in amplitude until becoming gravitationally unstable and generating a series of sinking plumes of relatively thick film. The plumes penetrate a finite distance into the film, giving rise to a turbulent mixed layer which slowly erodes the underlying region of stably stratified film. Note the black film adjoining the wire frame at the top of the film, and the relatively weak convective motions, associated with marginal regeneration, evident near the base of the film.
(*) The dynamics of wine -- In a wine glass, evaporation of alcohol creates Marangoni stresses that cause the wine to climb to the top of the thin film, where it accumulates in a band that grows until becoming gravitationally unstable and releasing the `tears of wine'.
(*) Fluid sheets and bells -- When a vertical water jet strikes a circular horizontal impactor, the water is deflected into a horizontal sheet. At sufficiently high speeds, the flow results in a circular water sheet, whose radius is set by a balance between inertial and curvature forces. At lower speeds, the sheet sags significantly under the influence of gravity, and may close, giving rise to a water bell. We have conducted a series of experiments in order to investigate the influence of increasing fluid viscosity on fluid sheets and bells.
(*) Fluid pipes(*) Colliding jets: chains and fishbones(*) Viscous hydraulic jumps(*) Skipping drops(*) Rotating fluid jets