Computational Fluid Dynamics model of stratified atmospheric boundary‐layer flow

For wind resource assessment, the wind industry is increasingly relying on computational fluid dynamics models of the neutrally stratified surface‐layer. So far, physical processes that are important to the whole atmospheric boundary‐layer, such as the Coriolis effect, buoyancy forces and heat transport, are mostly ignored. In order to decrease the uncertainty of wind resource assessment, the present work focuses on atmospheric flows that include stability and Coriolis effects. The influence of these effects on the whole atmospheric boundary‐layer are examined using a Reynolds‐averaged Navier–Stokes k‐ ε model. To validate the model implementations, results are compared against measurements from several large‐scale field campaigns, wind tunnel experiments, and previous simulations and are shown to significantly improve the predictions. Copyright © 2013 John Wiley & Sons, Ltd.     

Numerical study of different gas–solid flow regimes effects on hydrodynamics and heat transfer performance of a fluidized bed reactor

In this study, a two‐?uid Eulerian–Eulerian model has been carried out applying the kinetic theory of granular flow (KTGF) to study the hydrodynamics and heat transfer behavior of a fluidized bed reactor simultaneously. The effects of different gas–solid flow regimes on the operating conditions and heat transfer rate between the hot air and two types of low and high‐density inert particles are investigated in a fluidized bed dryer. Different gas–solid flow regimes for wood and glass particles of groups A, B, and D of Geldart's classification are simulated to introduce the most optimal flow regime in terms of heat transfer rate and operating costs. The compromise between the heating rate, the height required for the reactor, and the ratio of the final mass to the initial mass of solid particles, which specifies the need for a cyclone separator showed that the bubbling regime of Geldart B powder for low‐density particles and the turbulent regime of Geldart D powder or bubbling regime of Geldart B powder for high‐density particles are the optimal operating conditions and flow regimes. Furthermore, it was concluded that the convective heat transfer is the dominant mechanism, which increases with increasing the air velocity and decreasing the particle diameter in each group.