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Several experiments have already reported the existence of flow oscillations in a tight lattice bare rod-bundle. This in-turn results in temperature oscillations, when heat transfer is also involved. Consequently, assessment of flow oscillations plays an important role in the design of future innovative reactor systems as proposed by the Generation IV International Forum. Literature review reveals that such flow oscillations have recently numerically been analyzed using Unsteady Reynolds Averaged Navier-Stokes (URANS) and Large Eddy Simulation (LES) techniques. The objective is to assess...
Distributions in the concentration of reactant species in a PEMFC can cause distributions in local current density, temperature, and water content over the area of a PEMFC. These distributions can lead to effects such as flooding and MEA dehydration thus causing stresses in different regions of the fuel cell. Changing flow-field configurations and channel characteristics have been shown to also affect the cell performance and uniformity indistributions. This work investigates how performance and distributions in a baseline laboratory cell prepared by a precise machining method compared with...
Cavitation is a significant problem for the shipping industry as it can lead to ship vibration and erosion, both resulting in increased maintenance costs. Therefore, a better understanding of cavitation and an accurate prediction capability are important. Lloyd's Register has performed cavitation observations and measurements at ship scale and, from that, has developed a better understanding of cavitation and its effects, which are discussed in this paper. These observations showed that details of the cavitating flow are paramount for the erosive potential of the flow. Furthermore,...
Numerical investigations of turbulent natural convection between concentric, cylinders has been carried out. Large Eddy Simulations (LES) have been performed on three different geometries. The first two consider a single inner cylinder at gap-based Rayleigh numbers of 1.18×109 and 2.38×1010 and an aspect ratios Ro/Ri=4.87 and 3.37, respectively. The last LES run considers three internal cylinders. It reveals that the flow patterns in the decay heat pen are more complex than the one internal concentric cylinder cases. The two-equations RANS models predictions for this test case are less...
This study is related to mixed convection heat transfer of air flowing through an ascending vertical annular passage with significant radiation heat transfer. This configuration leads to a maximum level of heat transfer impairment similar to the one obtained in pipe flows. Five turbulence model predictions are compared with the experimental data obtained by the Promethée facility. Both k–w models (Wilcox and SST) tend to overestimate heat transfer in mixed convection while the standard low-Re number k-e underestimates it. The AKN low-Re model performs poorly in all cases. Finally, only the v²...
The paper surveys developments in CFD applications for maritime structures (ships, propellers and offshore structures) over the past decade. Progress is significant in integrating the process chain,particularly more automated model generation. Increased hardware power and progress in various aspects of the flow solvers allow more sophisticated applications and wider scope of applications.Selected examples taken from industry and research applications show the increasing importance of CFD in earlier design stages.
Probability density function (PDF) methods provide an elegant and effective resolution to the closure problems that arise from averaging or filtering chemical source terms and other nonlinear terms in the equations that govern chemically reacting turbulent flows. PDF methods traditionally have been associated with studies of turbulence-chemistry interactions in laboratory-scale, atmospheric pressure, nonluminous, statistically-stationary nonpremixed turbulent flames; and Lagrangian particle-based Monte Carlo numerical algorithms have become the predominant method for solving modeled PDF...

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