Topic
Wind shear
About: Wind shear is a research topic. Over the lifetime, 8023 publications have been published within this topic receiving 185373 citations.
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TL;DR: In this paper, a wind shear coefficient based on 1-h measured wind data has been performed by three stations located over coastal sites in Southern Italy, i.e., Brindisi (BR), Portoscuso (PS) and Termini Imerese (TI).
75 citations
TL;DR: This article evaluated the performance of convection-allowing models (CAMs) for the 2008 National Oceanic and Atmospheric Administration (NOAA) Hazardous Weather Testbed (HWT) spring experiment.
Abstract: This study assesses forecasts of the preconvective and near-storm environments from the convection-allowing models run for the 2008 National Oceanic and Atmospheric Administration (NOAA) Hazardous Weather Testbed (HWT) spring experiment. Evaluating the performance of convection-allowing models (CAMs) is important for encouraging their appropriate use and development for both research and operations. Systematic errors in the CAM forecasts included a cold bias in mean 2-m and 850-hPa temperatures over most of the United States and smaller than observed vertical wind shear and 850-hPa moisture over the high plains. The placement of airmass boundaries was similar in forecasts from the CAMs and the operational North American Mesoscale (NAM) model that provided the initial and boundary conditions. This correspondence contributed to similar characteristics for spatial and temporal mean error patterns. However, substantial errors were found in the CAM forecasts away from airmass boundaries. The result is...
74 citations
TL;DR: In this article, the authors present a very brief overview of the development of a three-dimensional hydrodynamic model involving a flow-dependent eddy viscosity and including enhancements of bottom friction due to wave-current interaction in shallow water.
Abstract: This paper presents a very brief overview of the development of a three-dimensional hydrodynamic model involving a flow-dependent eddy viscosity and including enhancements of bottom friction due to wave-current interaction in shallow water. The main point of the paper is to examine the physical nature of the process. Consequently, references to published work are given for the background detail. Calculations using both tidal and wind forcing show that tidal elevation amplitude and phase are significantly changed in shallow near-coastal regions due to enhanced frictional effects associated with wind-driven flow and wind wave turbulence. An analysis of tidal current profiles, at the fundamental harmonic and higher harmonies, computed with tidal and wind forcing, shows that significant changes in tidal current profiles can occur due to coupling between the wind-induced current shear and a time-evolving viscosity. The importance of the nonlinearity produced by a surface wind-induced shear and a flow-...
74 citations
01 Sep 1990
TL;DR: In this article, the importance of other variables in an analysis of power curves for three 2.5 MW wind turbines was discovered, and the sensitivity of the observed power curves was largely due to two factors: (1) an actual sensitivity to turbulence in determining the power curve and (2) the deviation of the disk-averaged velocity from the hub-height velocity under low turbulence conditions that were most prevalent at the site.
Abstract: It is a common practice to use wind speeds at hub height in determining wind turbine power curves. Although the possible influence of other variables (sub as turbulence and wind shear) is generally neglected in power curve measurements, we discovered the importance of other variables in an analysis of power curves for three 2.5 MW wind turbines. When the power curves were stratified by turbulence intensity. Such a large sensitivity to turbulence was not expected, and further analyses were conducted to determine if other factors accompanying the change in turbulence level could cause or contribute to the observed sensitivity of the power curves to turbulence. In summary, the sensitivity of the observed power curves was largely due to two factors: (1) an actual sensitivity to turbulence in determining the power curve and (2) the deviation of the disk-averaged velocity from the hub-height velocity under low turbulence conditions that were most prevalent at the site. An examination of the wind shear profiles over the height of the rotor disk revealed that low turbulence conditions were characterized by strong shear in the lower half of the rotor disk and weak or negative shear in the upper half. Implications of this analysis aremore » that significant errors in power curve measurements can result if the effects of wind shear and turbulence are ignored. 7 refs., 6 figs.« less
74 citations
TL;DR: In this paper, the authors investigated the effect of wind incidence angle on flow field characteristics in the wake of a wind barrier and found that removing elements from the wind barrier causes very large local velocities immediately downstream from a barrier and strong vorticity in the entire area.
74 citations