Kelvin–Helmholtz instability in a Hele-Shaw cell

A linear stability analysis is presented for the Kelvin–Helmholtz instability in a Hele-Shaw cell, an analysis based on the Navier–Stokes equation to improve on the previous Euler–Darcy study that Gondret and Rabaud [Phys. Fluids 9, 3267 (1997)] made of their own experiments

Kelvin–Helmholtz instability in a Hele-Shaw cell: Large effect from the small region near the meniscus

In an attempt to improve the poor prediction of our previous theory, we examine corrections from the small region in a Hele-Shaw cell near the meniscus where the flow is three dimensional. At larger Reynolds numbers, we find an O(1) change to the effective boundary condition for mass conservation which is to be applied to the large scale flow outside the small region

Conceptual models of the climate : 2003 program of study, Non-Newtonian geophysical fluid dynamics

Non-Newtonian fluids occur commonly in our world. These fluids, such as toothpaste, saliva, oils, mud and lava, exhibit a number of behaviors that are different from Newtonian fluids and have a number of additional material properties. In general, these differences arise because the fluid has a microstructure that influences the flow. In section 2 we will present a collection of some of the interesting phenomena arising from flow nonlinearities, the inhibition of stretching, elastic effects and normal stresses. In section 3 we will discuss a variety of devices for measuring material properties, a process known as rheometry.Funding was provided by the Office of Naval Research under Contract No. N00014-97-1-0934 and The National Science Foundation under Contract No. OCE 98-10647

Measuring glucose content in the aqueous humor

Many diabetics must measure their blood glucose levels regularly to maintain good health. In principle, one way of measuring the glucose concentration in the human body would be by measuring optically the glucose content of the aqueous humor in the eye. Lein Applied Diagnostics wish to assess whether this is feasible by a linear confocal scan with an LED source, or by supplementing such a system with other measurements

Spreading fronts and fluctuations in sedimentation

International audienceA diffuse interface or ''front'' at the top of the suspension is investigated experimentally and numerically. The width of the front is found to grow linearly in time, mainly due to a polydispersity of particle size in the very dilute experiments, and due only to fluctuations in particle density in the simulations. Away from the front, the fluctuations in the particle velocities are found not to decay

On stratification control of the velocity fluctuations in sedimentation

International audienceWe have tested whether stratification can govern local velocity fluctuations in suspensions of sedimenting spheres. Comparison of the proposed scaling for local control of fluctuations by stratification to experimental data demonstrates that this mechanism cannot account for the reduction of the observed velocity fluctuations

Fluctuations and stratification in sedimentation of dilute suspensions of spheres

International audienceWe have tested in experiments and simulations whether stratification can control velocity fluctuations in suspensions of sedimenting spheres. The initial value and early decay of the velocity fluctuations are not affected by stratification. On the other hand, in the descending front where the stratification is strong and well defined, the velocity fluctuations are inhibited according to a previously proposed scaling. In between, after the initial decay and before the arrival of the front, the local value of the stratification does not always play a role

Spreading fronts in sedimentation of dilute suspension of spheres

International audienceThe thickness of the diffuse front between a sedimenting dilute suspension and the clear fluid above grows linearly in time due to polydispersity in the size of the particles and due to a hydrodynamic effect in which randomly heavy clusters fall out of the front leaving it depleted. Experiments and simplified point-particle numerical simulations agree that these two effects are not simply linearly additive

The S shape of a granular pile in a rotating drum

The shape of a granular pile in a rotating drum is investigated. Using Discrete Elements Method (DEM) simulations we show that the "S shape" obtained for high rotation speed can be accounted for by the friction on the end plates. A theoretical model which accounts for the effect of the end plates is presented and the equation of the shape of the free surface is derived. The model reveals a dimensionless number which quantifies the influence of the end plates on the shape of the pile. Finally, the scaling laws of the system are discussed and numerical results support our conclusions

Changes in Body composition and Maintenance efficiency during periods of restricted and maintenance feeding in immature and mature sheep

Improvements in production and quality can occur, without the need for increased inputs, through the use of 'Compensatory growth' or by reducing the maintenance requirements during growth and at maturity. A series of studies were used to examine the changes in body composition that occurred during weight loss and realimentation in immature and mature sheep. The effect of variations in body composition, induced through manipulation of nutrition, on estimates for equilibrium maintenance efficiency of mature sheep was examined. Statistical methods developed, tested for seasonal cycles in body composition in an attempt to determine the impact that any endogenous pattern in tissue deposition has on estimates of efficiencies for growth and maintenance. ..... Seasonality After adjusting for differences in body composition attributable to growth using an allometric function, seasonal oscillations for total body fat and carcass muscle were apparent in growing sheep. The magnitude and phase of the sine oscillations for fat and carcass muscle suggested that seasonal cues affect the priorities for tissue deposition. Seasonal oscillations where present for mature sheep that had been fed at a constant feed level. However a more precise method of describing the patterns of change in body tissues using random effects models and cubic splines did not reveal the presence of any time based deviation in total fat, carcass muscle or visceral lean. Nevertheless, the possibility of oscillations in body composition must be considered when estimating the efficiency of growth and maintenance or when evaluating the effects of nutritional manipulation on tissue development in immature and mature sheep