CiteULike: Author Baroud

Thermocapillary manipulation of droplets using holographic beam shaping: Microfluidic pin ball

Maria Cordero — 2008-08-07T17:26:35-00:00

Applied Physics Letters, Vol. 93, No. 3. (2008)

Experimental and numerical studies of an eastward jet over topography

Yudong Tian — 2008-06-18T01:27:04-00:00

Journal of Fluid Mechanics, Vol. 438, No. -1. (2001), pp. 129-157.

Motivated by the phenomena of blocked and zonal flows in Earth's atmosphere, we conducted laboratory experiments and numerical simulations to study the dynamics of an eastward jet flowing over wavenumber-two topography. The laboratory experiments studied the dynamical behaviour of the flow in a barotropic rotating annulus as a function of the experimental Rossby and Ekman numbers. Two distinct flow patterns, resembling blocked and zonal flows in the atmosphere, were observed to persist for long time intervals. Earlier model studies had suggested that the atmosphere's normally upstream- propagating Rossby waves can resonantly lock to the underlying topography, and that this topographic resonance separates zonal from blocked flows. In the annulus, the zonal flows did indeed have super-resonant mean zonal velocities, while the blocked flows appear subresonant. Low-frequency variability, periodic or irregular, was present in the measured time series of azimuthal velocity in the blocked regime, with dominant periodicities in the range of 6–25 annulus rotations. Oscillations have also been detected in zonal states, with smaller amplitude and similar frequency. In addition, over a large region of parameter space the two flow states exhibited spontaneous, intermittent transitions from the one to the other. We numerically simulated the laboratory flow geometry in a quasi-geostrophic barotropic model over a similar range of parameters. Both flow regimes, blocked and zonal, were reproduced in the simulations, with similar spatial and temporal characteristics, including the low-frequency oscillations associated with the blocked flow. The blocked and zonal flow patterns are present over wide ranges of forcing, topographic height, and bottom friction. For a significant portion of parameter space, both model flows are stable. Depending on the initial state, either the blocked or the zonal flow is obtained and persists indefinitely, showing the existence of multiple equilibria.

Capillary Origami: Spontaneous Wrapping of a Droplet with an Elastic Sheet

Charlotte Py — 2008-05-04T18:50:09-00:00

Physical Review Letters, Vol. 98, No. 15. (2007)

The interaction between elasticity and capillarity is used to produce three-dimensional structures through the wrapping of a liquid droplet by a planar sheet. The final encapsulated 3D shape is controlled by tailoring the initial geometry of the flat membrane. Balancing interfacial energy with elastic bending energy provides a critical length scale below which encapsulation cannot occur, which is verified experimentally. This length is found to depend on the thickness as h3/2, a scaling favorable to miniaturization which suggests a new way of mass production of 3D micro- or nanoscale objects.

Experimental and theoretical investigation of directional permeability of human vertebral cancellous bone for cement infiltration

G Baroud — 2004-12-28T17:06:36-00:00

Journal of Biomechanics, Vol. 37, No. 2. (February 2004), pp. 189-196.