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The oro-pharyngeal-laryngeal human airway is a complex geometry; the flow physics within are subjected to and influenced by a variety of different factors that produce jet-like flow, re-circulating flows that are enhanced by curvature, detached and secondary flows. Simulation and experiment are the tools available to the fluid dynamics researcher. Simulation results obtained from direct and large-eddy simulation, and Reynolds-averaged Navier–Stokes and associated models of turbulence are reviewed. Experimental data obtained through the use of flow visualisation, hot-wire anemometry and particle image velocimetry are also reviewed. A comparison of data obtained from the application of these tools reveals many inconsistencies that are explored in this article. While much progress has been made to understand some of the physics of the flow in the human airway, we continue to uncover new and significant fluid dynamic behaviour. Finally, future research directions are suggested. [ABSTRACT FROM AUTHOR]

Viscous incompressible fluid flow along the clearance between two parallel eccentric circular cylinders is studied numerically. The geometric parameters and the Reynolds number are taken so that the turbulent flow regime takes place in a part of flow, namely, in the zone where the clearance is wide, while the low is laminar in the narrow clearance zone. Criteria using which these zones can be distinguished are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a study of electromagnetic stirring using rotating and travelling magnetic fields, including superpositions with either different or identical frequencies. The resulting turbulent flow was investigated by means of direct numerical simulations based on the low-frequency/low-induction limit of the magnetohydrodynamic equations. The rotating magnetic field drives a vigorous swirling flow with turbulence governed by Taylor-Goortler vortices and, hence, largely confined to the wall region. In contrast, the travelling field yields a meridional circulation, which is accompanied by strong fluctuations that amount to about one half of the total kinetic energy. If the fields are superimposed with comparable forcing parameters but different frequencies, the rotating field prevails although symmetry is broken by the uneven distribution of angular momentum caused by the travelling field. Superposition with identical frequencies leads to a genuinely three-dimensional flow, which holds a promise for high mixing efficiency. [ABSTRACT FROM AUTHOR]

Abstract: A computational fluid dynamics (CFD) code was applied to an America''s Cup Class Yacht to investigate sailing performance in a downwind configuration. Apparent wind angles at 45°, 105° and 120° are reported, sailed with mainsail and asymmetrical spinnakers. Numerical results are in good agreement with wind tunnel data. A large mesh investigation was performed, ranging from 60,000 elements up to 37 million elements, which shows a converging trend to the experimental values with differences smaller than 3% in both lift and drag. The most commonly used turbulence models in sail applications were tested and the results are presented here in two meshes with 1 million elements and 6.5 millions, respectively. All turbulence models over-estimate forces more than solving the Navier–Stokes system without any additional equations, hence turbulence models do not increase solution accuracy according to these results. [Copyright &y& Elsevier]

Direct numerical simulation of uniform shear flow is used to study the anisotropy of fluctuating motion in a stably stratified medium with uniform mean shear. Turbulence is found to be three dimensional over a wide range of gradient Richardson numbers in the two flows investigated here: vertical mean shear (SHAPE="BUILT" ALIGN="C" STYLE="S">dUdz and horizontal mean shear (SHAPE="BUILT" ALIGN="C" STYLE="S">dUdy. The role of the turbulent Froude number in establishing the regime of stratified turbulence observed here is described. The fluctuating velocity gradients are examined. The vertical of streamwise velocity is found to dominate the other components of turbulent dissipation in both horizontal and vertical shear flows. [Copyright &y& Elsevier]

In the thermal and fluid science, multiscale problems may be classified into two categories: multiscale process and multiscale system. In the multiscale process the overall behaviour is governed by the processes that occur on different length/time scales and are inherently related. Turbulent flow is an example. By multiscale system, we refer to a system that is characterised by large variation in length scales, for which the processes at different length scales are not so closely related. The cooling of an electronic system is an example. In this paper, recent advances in the numerical simulations of the first categories are presented. [ABSTRACT FROM AUTHOR]