In this paper, a fully implicit numerical model of the three-dimensional thermoha-

With the recent developments in the solution methods for large-dimensional nonlinear algebraic systems, fullyimplicit ocean circulation models are now becoming feasible. In this paper, the formulation of such a three-dimensional global ocean model is presented. With this implicit model, the sensitivity of steady states to parameters can be investigated efficiently using continuation methods. In addition, the implicit formulation allows for much larger time steps than can be used with explicit models. To demonstrate current capabilities of the implicit global ocean model, we use a relatively low-resolution (4°horizontally and 12 levels vertically) version. For this configuration, we present: (i) an explicit calculation of the bifurcation diagram associated with hysteresis behavior of the ocean circulation and (ii) the scaling behavior of the Atlantic meridional overturning versus the magnitude of the vertical mixing coefficient of heat and salt.

A first-order discussion of convective heat removal from a hypothetical 3-dimensional computing system is presented. A textbook treatment indicates that our heat removal capability can be characterized by a quantity Q, the amount of power we can remove per unit cross-section. Thus the minimum length of the system is proportional to the square root of the total power dissipated. We predict Q ∼ 104Wcm−2 assuming an applied pressure difference of 1 atm, a maximum temperature rise of 100K and the use of water as the coolant fluid. © 1992 Taylor & Francis Ltd

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AC electrothermal (ET) flow is inevitable for microfluidic systems dissipating electric energy in a conducting medium. Therefore, many practical applications of biomicrofluidics are prone to ET flow. Here, a series of observations are reported on ET flow in a microfluidic chamber that houses three electrode pairs. The observations indicate that the variations in liquid conductivity and channel height critically impact the structure and magnitude of the flow field. Observations indicate that after a critical conductivity a global ET flow is present in the chamber, while at lower conductivities a vortex is present at every electrode edge. In addition, no ET flow is observed when the chamber height is kept below a critical value at physiological conductivity (∼1.5 S/m). The experimental observations are compared with the numerical simulations of ET flow. The validity of the assumptions made in the current AC ET flow theory is also discussed in the light of the experimental data. The observations can be critical while designing microfluidic systems that involve power dissipation in conductive fluids.