Wind shear

About: Wind shear is a research topic. Over the lifetime, 8023 publications have been published within this topic receiving 185373 citations.

Influence of different wind profiles due to varying atmospheric stability on the fatigue life of wind turbines

Abstract: Offshore wind energy is being developed on a very large scale in the European seas. The objective of developing wind energy offshore is to capture greater wind speeds than are encountered onshore and as a result more energy. With this also come more challenges in the design of wind turbines due to the hostile offshore environment. Currently the standards for offshore wind turbines prescribe a site specific design for the support structures and the design for the rotor nacelle assembly according to onshore standards. Wind turbines are designed to withstand fatigue and ultimate loads. For the fatigue loading several input conditions have been prescribed, amongst which wind profile is one of them. Wind profile is represented by power law or logarithmic law as given in the standards. A neutral stability of the atmosphere is considered while obtaining the wind profile using the logarithmic law. In this paper the atmospheric stability is varied in order to estimate different wind profiles and simulations are run in Bladed to check its influence on the fatigue damage at the blade root. The variations in the atmospheric stability has been taken into account by using some typical values of Obukhov length. From steady state simulations it has been found that atmospheric stability is important for fatigue damage. The analysis showed that variation in the distribution of atmospheric stability causes large variations in the fatigue damage for different sites. Thus, it is worthwhile to carry out a full scale study using the turbulent winds and real data for wind turbine and environmental conditions.

Influence of the Upper-Tropospheric Wind Shear upon Cloud Radiative Forcing in the Asian Monsoon Region

Abstract: Using the top-of-the-atmosphere radiative flux and cloud data from satellites, as well as atmospheric data from NCEP–NCAR reanalysis, this paper investigates the reason for the unusually large high-cloud amount in the Asian monsoon region during the summer monsoon season (June–September). Earlier studies attributed the large negative net cloud radiative forcing in the Asian monsoon region to the unusually large high-cloud amounts with high optical depth. Analysis during 1985–89 suggests that the unique upper-tropospheric easterly wind shear [tropical easterly jet (TEJ)], present over the Asian monsoon region during the summer monsoon season, may be responsible for the unusual increase in cloud amount. This strong wind shear sweeps the cloud tops and may be unfavorable for cloud growth beyond about 300 hPa. The spreading of cloud tops by wind may increase the high-cloud amount. A significant association is found between the high-cloud amount and the speed of the easterly jet. In addition, magnitud...

Generation of Bulk Shear Spikes in Shallow Stratified Tidal Seas

Abstract: Recent finescale observations of shear and stratification in temperate shelf sea thermoclines show that they are of marginal stability, suggesting that episodes of enhanced shear could potentially lead to shear instability and diapcynal mixing. The bulk shear between the upper and lower boundary layers in seasonally stratified shelf seas shows remarkable variability on tidal, inertial, and synoptic time scales that has yet to be explained. In this paper observations from the seasonally stratified northern North Sea are presented for a time when the water column has a distinct two-layer structure. Bulk shear estimates, based on ADCP measurements, show a bulk shear vector that rotates in a clockwise direction at the local inertial period, with episodes of bulk shear spikes that have an approximately twice daily period, and occur in bursts that last for several days. To explain this observation, a simple two-layer model based on layer averaging of the one-dimensional momentum equation is developed, ...

Full vector (3-D) inflow simulation in natural and wind farm environments using an expanded version of the SNLWIND (Veers) turbulence code

Abstract: We have recently expanded the numerical turbulence simulation (SNLWIND) developed by Veers [1] to include all three components of the turbulent wind vector We have also configured the code to simulate the characteristics of turbulent wind fields upwind and downwind of a large wind farm, as well as over uniform, flat terrain Veers's original method only simulates the longitudinal component of the wind in neutral flow This paper overviews the development of spectral distribution, spatial coherence, and cross correlation models used to expired the SNLWIND code to include the three components of the turbulent wind over a range of atmospheric stabilities These models are based on extensive measurements of the turbulence characteristics immediately upwind and downwind of a large wind farm in San Gorgonio Pass, California

A model for large‐scale convective storms in Jupiter

Abstract: [1] Large-scale convective storms are a common phenomenon in Jupiter's atmosphere. They are apparent in ground-based and spacecraft images and may strongly affect the dynamics of the global atmosphere as well as the energy transport in the meteorological layer. In this paper we analyze the outburst of a large convective storm system (core ∼5000 km) in the South Equatorial Belt (SEB) that was observed at high spatial and temporal resolution by the Voyager 1 spacecraft in 1979. We use a two-dimensional (2-D) model to study the interaction between cloud material brought up by moist convection and the environmental wind. Aided by previous 3-D models of Jovian storms, we can draw several qualitative and quantitative conclusions. The evolution of this storm can be characterized by three phases: (1) onset of the perturbation, well reproduced by the growth of a single-cell storm; (2) an expanding phase in which the number of convective cells increases to ∼200, with updraft velocities limited to 50 m/s; and (3) a relatively sudden suppression of the convective activity leading to the disruption of large structures by the environmental wind. Furthermore, we interpret the observations of the inner bright core as a well-defined anticyclonic vortex, with darker cloud material preferentially left southwest of the system. Finally, we show that ∼1016 W are released by such a storm over its life cycle of 12 days and that the direct formation of a large-scale anticyclonic vortex after the moist convective source has been removed is prevented by the environmental wind shear.