Showing papers on "Wind profile power law published in 2001"
TL;DR: The high-resolution Doppler lidar (HRDL) was developed to provide higher spatial, temporal, and velocity resolution and more reliable performance than was previously obtainable with CO2-laser-based technology as discussed by the authors.
Abstract: The high-resolution Doppler lidar (HRDL) was developed to provide higher spatial, temporal, and velocity resolution and more reliable performance than was previously obtainable with CO2-laser-based technology. The improved performance is needed to support continued advancement of boundary layer simulation models and to facilitate high-resolution turbulent flux measurements. HRDL combines a unique, eye-safe, near-IR-wavelength, solid-state laser transmitter with advanced signal processing and a high-speed scanner to achieve 30-m range resolution and a velocity precision of ∼10 cm s−1 under a variety of marine and continental boundary layer conditions, depending on atmospheric and operating conditions. An attitude-compensating scanner has been developed to facilitate shipboard marine boundary layer observations. Vertical velocities, fine details of the wind profile near the surface, turbulence kinetic energy profiles, and momentum flux are measurable with HRDL. The system is also useful for cloud s...
237 citations
TL;DR: In this paper, a 6-m cube has been constructed at Silsoe Research Institute in an open country exposed position and detailed measurements have been made of surface pressure on the cube and of the wind velocities in the region around the cube.
145 citations
TL;DR: In this paper, the authors conducted simulations using varying thermal and wind profile shapes, subject to the constraints of strict conservation of convective available potential energy (CAPE) and hodograph trace.
Abstract: Convective storm simulations are conducted using varying thermal and wind profile shapes, subject to the constraints of strict conservation of convective available potential energy (CAPE) and hodograph trace. Small and large CAPE regimes and straight and curved hodographs are studied, each with a matrix of systematically varying thermal and wind profile shapes having identical levels of free convection and bulk Richardson numbers favorable to supercell development. Differences in storm intensity and morphology resulting from changes in the profile shapes can be profound, especially in the small CAPE regime, where, for the moderate shears studied here, storms are generally weak except when the buoyancy is concentrated at low levels. In stronger CAPE regimes, less dramatic relative enhancements of storm updraft intensity are found when both the buoyancy and shear are concentrated at low levels. Peak midlevel vertical vorticity correlates roughly with peak updraft speed in the small CAPE regime, but...
133 citations
TL;DR: In this paper, the authors presented a novel method of matching wind turbine generators to a site using normalized power and capacity factor curves, based on identifying optimum turbine speed parameters from the turbine performance index curve, which is obtained from the normalized curves, so as to yield higher energy production at a higher capacity factor.
Abstract: This paper presents a novel method of matching wind turbine generators to a site using normalized power and capacity factor curves. The site matching is based on identifying optimum turbine speed parameters from the turbine performance index curve, which is obtained from the normalized curves, so as to yield higher energy production at a higher capacity factor. The wind speeds are parameterized using a cubic mean cuberoot and statistically modeled using the Weibull probability density function. An expression for a normalized power and capacity factor, expressed entirely in normalized rated speed, is derived. The wind turbine performance index, a new ranking parameter, is defined to optimally match turbines to a potential wind site. The plots of normalized power, capacity factor, and turbine performance index versus normalized rated wind speed are drawn for a known value of the Weibull shape parameter of a site. Usefulness of these normalized curves for identifying optimum wind turbine generator parameters for a site is presented by means of two illustrative case studies. The generalized curves, if used at the planning and development stages of wind power stations, will serve as a useful tool to make a judicious choice of a wind turbine generator that yields higher energy at a higher capacity factor.
126 citations
TL;DR: In this paper, the influence of wind shear, wind speed, turbulence intensity, rotor position and tower oscillation on the power pulsation of a three-bladed wind turbine is investigated.
Abstract: In this paper, periodic power pulsations from a three-bladed wind turbine are analyzed. The influence of wind shear, wind speed, turbulence intensity, rotor position and tower oscillation is investigated. No clear dependence between the periodic power components and the wind shear or turbulence intensity has been verified. The investigated turbine sometimes produces large power pulsations at the tower resonance frequency. These occur when the turbine oscillates in the sideways direction of the nacelle.
103 citations
TL;DR: In this article, the first measurements of wind velocities at northern latitudes not accessible to the Voyager cameras and new measurements of southern latitudes determined during the 1986 Voyager encounter were obtained.
78 citations
TL;DR: In this article, a method for the optimization of a grid-connected wind turbine system is presented, where the behavior of the system components is coupled in a non-linear way, and optimization must take into account technical and economical aspects of the complete system design.
Abstract: A method for the optimization of a grid-connected wind turbine system is presented. The behaviour of the system components is coupled in a non-linear way, and optimization must take into account technical and economical aspects of the complete system design. The annual electrical energy cost is estimated using a cost model for the wind turbine rotor, nacelle and tower and an energy output model based on the performance envelopes of the power coefficient of the rotor, CP, on the Weibull parameters k and c and on the power law coefficient α of the wind profile. In this study the site is defined with these three parameters and the extreme wind speed Vmax. The model parameters vary within a range of possible values. Other elements of the project (foundation, grid connection, financing cost, etc.) are taken into account through coefficients. The optimal values of the parameters are determined using genetic algorithms, which appear to be efficient for such a problem. These optimal values were found to be very different for a Mediterranean site and a northern European site using our numerical model. Optimal wind turbines at the Mediterranean sites considered in this article have an excellent profitability compared with reference northern European wind turbines. Most of the existing wind turbines appear to be well designed for northern European sites but not for Mediterranean sites. Copyright © 2001 John Wiley & Sons, Ltd.
76 citations
TL;DR: In this article, Eulerian autocorrelation functions were computed for the horizontal and vertical wind velocity fluctuations for low wind speeds, and a Lagrangian dispersion model with random time steps and a negative intercorrelation parameter was used to take the first of the above-mentioned findings into account.
Abstract: Sonic anemometer observations were made 10 m above ground level for a period of 1 yr. From these data, Eulerian autocorrelation functions were computed for the horizontal and vertical wind velocity fluctuations for low wind speeds. Although the autocorrelation function for the vertical velocity component exhibited the well-known exponential form, the function for the horizontal components of the wind vector showed a negative loop for all stability classes at low wind speeds. This result might be an effect of low-frequency meandering of the flow. Observations of the standard deviations of the vertical wind component confirmed the proportionality with the friction velocity, though with a slightly lower constant of proportionality than has been found by other authors. A Lagrangian dispersion model (LDM) with random time steps and a negative intercorrelation parameter ρu,υ for the horizontal wind components was used to take the first of the above-mentioned findings into account. In a simple test case...
74 citations
TL;DR: The first flights on board the DLR Falcon 20 aircraft were performed in 1999 as discussed by the authors, which is the first airborne Doppler lidar for atmospheric research to retrieve the whole tropospheric wind profile between the ground and the flight level looking downward.
Abstract: The airborne Wind Infrared Doppler Lidar (WIND) has been developed through French–German cooperation. The system is based on a pulsed 10.6-μm laser transmitter, a heterodyne receiver, and a conical scanning device. To the authors' knowledge, it is the first airborne Doppler lidar for atmospheric research to retrieve the whole tropospheric wind profile between the ground and the flight level looking downward. The wind vector is measured with the velocity-azimuth display (VAD) technique with a vertical sampling of 250 m. The first flights on board the DLR Falcon 20 aircraft were performed in 1999. Results of a comparison among WIND, radiosondes, wind-profiler radar measurements, numerical models, and simulations are presented. It is shown that the correspondence of airborne WIND measurements with those of other instruments or models is better than 1.5 m s−1 and 5° for the horizontal wind vector. These results show the excellent capability of conical scanning Doppler lidars to provide unique insight...
72 citations
TL;DR: In this paper, a probabilistic methodology for developing improved load factors in standard provisions for wind loads is proposed, and the authors use it to examine: the cause of the discrepancy noted in the 1980s between estimates of safety indices for wind and gravity loads; the relative magnitude of load factors for hurricane and non-hurricane regions; and the effect of the length of wind tunnel pressure records on the estimation of peak wind effects.
70 citations
TL;DR: In this article, the results of a previous measurement campaign near a major road at ElimaK ki in southern Finland in 1995, a campaign speci cally designed for model evaluation purposes, were compared with the measured and predicted data sets, as measured using various statistical parameters.
TL;DR: In this article, the authors examined the effect of the scale of turbulence on the response of a line-like structure (cable model) through wind tunnel tests and compared theoretical predictions made through the statistical method using influence lines.
TL;DR: The hypothesis that the safety factor against wind-induced stem failure remained high during early land plant evolution despite an evolutionary increase in height with concomitant increases in wind- induced drag forces, bending stresses, and moments is explored.
Abstract: We explore the hypothesis that the safety factor against wind-induced stem failure remained high during early land plant evolution despite an evolutionary increase in height with concomitant increases in wind-induced drag forces, bending stresses, and moments. This hypothesis was examined for 17 Paleozoic plant species assuming that each (1) existed in a densely packed community of conspecifics with equivalent height, (2) coped with the same wind profile (where ambient wind speed decreased toward ground level), but (3) had different within-canopy wind speeds depending on plant height and general morphology. Drag forces, stresses, and moments were computed, and a safety factor was calculated for each taxon using the quotient of its stem-tissue breaking stress and maximum wind-induced bending stress. The highest factors of safety were calculated among the most ancient rhyniophyte and zosterophyllophyte species examined (e.g., Rhynia and Gosslingia), and, on average, decreased among the taller and geologically younger species. The tallest species examined (e.g., Archaeopteris and Diaphorodendron) had safety factors equal to or higher than those of some of their presumed ancestors (e.g., Psilophyton and Leclercqia). These trends were statistically more robust among rhyniophytes and their presumed descendants. Even though the results comply with the hypothesis, numerous limitations of our protocol exist (e.g., the requirement for reliable whole-plant reconstructions). These are discussed in terms of our theory. Nonetheless, we believe our theory and protocol afford a reasonable opportunity to explore the effects of wind on early plant evolution.
TL;DR: In this article, the authors describe a method aimed at providing an estimate of the real wind directly from aliased wind measurements without prior dealiasing, allowing the method to be used in real time by operational radars without additional information from other instruments.
Abstract: Doppler radar measurements provide the radial wind within an unambiguous interval due to the limited value of the sampling frequency (pulse repetition frequency). Many algorithms have been developed to retrieve true wind velocities from measured aliased wind velocities. However, these algorithms are time consuming, which can be a constraint in an operational context. Besides, most of them need independent information on the wind generally provided by complementary neighbor measurements such as radiosonde or wind profiler. This paper describes a new method aimed at providing an estimate of the real wind directly from aliased wind measurements without prior dealiasing, allowing the method to be used in real time by operational radars without additional information from other instruments. A potential application of the method is to provide a reference wind profile that can be used, in a second step, to dealias radial velocities.
TL;DR: In this paper, a wind turbine nozzle is designed as an aerodynamically shaped ring with wings with its lower pressure side pointed towards the center so that the lift force on each part of the wing is directed radially towards the centre.
TL;DR: In this paper, the effect of short-term variability on air-sea CO2 flux was investigated using high sampling frequency wind speed and pCO2 data collected during deployments of the autonomous CARbon Interface OCean Atmosphere (CARIOCA) buoy.
Abstract: Quantifying the regional and global exchange of CO2 between the ocean and atmosphere requires knowledge of the factors that affect CO2 gas transfer (e.g., wind speed) and the air-sea difference in partial pressure of CO2 (pCO2). A major uncertainty is the effect of short-term variability on air-sea CO2 flux. Using high sampling frequency wind speed and pCO2 data collected during deployments of the autonomous CARbon Interface OCean Atmosphere (CARIOCA) buoy, we compare CO2 fluxes at different sampling frequency of wind speed (i.e., hourly versus daily averaged). Air-sea CO2 flux was up to three times greater if high frequency wind data was used rather than daily average values. This difference arises from the non-linear relationship between wind speed and CO2 gas transfer coefficient, and a better representation of wind distribution at a higher frequency (i.e., hourly) of sampling. This finding has significant implications for determining regional and global air-sea CO2 fluxes, and understanding of the global carbon cycle.
TL;DR: In this paper, the power quality impact of a 2.5 MW wind park has been measured and analyzed, and the turbines in the park operate at variable speed at low wind speeds and at fixed speed at higher wind speeds.
Abstract: The power quality impact of a 2.5 MW wind park has been measured and analyzed. The turbines in the park operate at variable speed at low wind speeds and at fixed speed at higher wind speeds. The harmonic current injection is low and the calculated flicker contribution is seldom above 0.25. The wind park also has the potential to maintain the voltage on the supplying grid below a certain limit, in this case 11 kV.
TL;DR: In this article, the cause and effect relationship between the incident wind, the conical vortices, and the induced roof-corner high-suction pressures has been confirmed through analyzing the simultaneously collected wind and pressure data and the synchronized conical-vortex images.
TL;DR: In this paper, the conditionally sampled actual wind pressure distributions causing maximum quasi-static wind load effects at the base of low-rise building models with square and rectangular plans were discussed.
TL;DR: In this paper, the authors propose a comparative criterion adapted to the comparison of a horizontal axis wind turbine with a vertical axis wind turbines: the L −σ criterion, which consists in comparing wind turbines which intercept the same front width of wind, by allocating them a same reference value of the maximal mechanical stress on the blades or the paddles.
TL;DR: In this paper, the authors examined the domain-average momentum budgets in several multiday cloud-resolving model simulations of deep tropical convection in realistic shears, and showed that the portion of F in phase with the mean wind is isolated by vertically integrating F, yielding a kinetic energy tendency that is overwhelmingly negative.
Abstract: Domain-average momentum budgets are examined in several multiday cloud-resolving model simulations of deep tropical convection in realistic shears. The convective eddy momentum tendency F, neglected in many global circulation models, looks broadly similar in two- and three-dimensional simulations. It has a large component in quadrature with the mean wind profile, tending to cause momentum profile features to descend. This component opposes, and exceeds in magnitude, the corresponding large-scale vertical advective tendency, which would tend to make features ascend in convecting regions. The portion of F in phase with the mean wind is isolated by vertically integrating F · u, yielding a kinetic energy tendency that is overwhelmingly negative. The variation of this energy damping with shear flow kinetic energy and convection intensity (measured by rain rate) gives a “cumulus friction” coefficient around −40% to −80% per centimeter of rain in 3D runs. Large scatter reflects the effects of varying co...
TL;DR: In this article, a model is proposed which calculates the snow transport over a two-dimensional mountain ridge, based on input measurements of wind speed and precipitation, and no statements are made about the exact snow distribution over the slopes.
Abstract: Wind transport of snow can cause an additional snow load on leeward slopes, which often has a considerable influence on avalanche danger For a quantitative assessment of this process, a model is proposed which calculates the snow transport over a two-dimensional mountain ridge, based on input measurements of wind speed and precipitation Since the topography is idealized, the model is focused on the snow mass that is transported over the ridge, and no statements are made about the exact snow distribution over the slopes Three transport modes are distinguished: snow transport in saltation, snow transport in Suspension, and preferential deposition of precipitation Suspension is modelled with a one-dimensional diffusion equation, and for the saltation layer a newly developed model, based on the microscale physical processes, is implemented The effect of speed-up of the wind over the ridge is included by assuming an analytical wind profile with a maximum wind speed at a few meters above the ridge Advective effects are taken into account in a parameterization of the turbulent shear stress profile The model is compared with measurements taken at the experimental snowdrift site Gaudergrat in the Parsenn area, Switzerland, and good agreement is obtained between calculated and measured results
TL;DR: In this paper, the authors presented a procedure for the calculation of wind loads on a proposed 385'ft tall building located in strong wind and mixed strong wind, and hurricane wind regions, using mixed distribution and Monte Carlo simulation.
Abstract: This paper presents a procedure for the calculation of wind loads on a proposed 385 ft tall building located in strong wind and mixed strong wind and hurricane wind regions. The procedure for the computation of design wind loads uses mixed distribution and Monte Carlo simulation. The results of a probabilistic analysis of hurricane wind speeds are combined with the probability distribution of recorded extreme wind speeds (excluding hurricane data) at the site. A 50-year sample of extreme wind speeds is created and the maximum 50-year wind (from the hurricane and the recorded data) is noted. The simulation is repeated for a large number of samples (>10000) and the probability distribution of the 50-year wind speed is computed for use in establishing the design wind speed Copyright © 2001 John Wiley & Sons, Ltd.
DOI•
01 Jan 2001
TL;DR: In this article, it was shown that Vilsandi wind data represent satisfactorily both scalar and directional properties of the wind regime in the Baltic Proper, and that the angular distribution of wind speed in extreme wind events (based on the Weibull distribution) has a specific two-peaked shape with maxima corresponding to south-west and north winds, and a deep minimum for eastearly winds.
Abstract: It is shown that Vilsandi wind data represent satisfactorily both scalar and directional properties of the wind regime in the Baltic Proper. Angular distribution of the wind speed in extreme wind events (based on the Weibull distribution) has a specific two-peaked shape with maxima corresponding to south-west and north winds, and a deep minimum for eastearly winds. Extensive periods in which wind direction is uniform over large areas, frequently occur in the Baltic Proper. Both wind speed and direction may essentially change during such events, but the changes may occur synchronously at remote sites.
TL;DR: This work reanalyzes high resolution wind data and demonstrates the fractal character of the point process generated by the wind speed level crossings and simulates the fluctuating wind speed by a Markov process which approximates the characteristics of the real (non-Markovian) wind and successfully generates a power law distribution of episode lengths.
Abstract: The probability density of the times for which the horizontal wind remains above or below a given threshold speed is of some interest in the fields of renewable energygeneration and pollutant dispersal. However there appear to be no analytic or conceptual models which account for the observed power law form of the distribution of these episode lengths over a range of over three decades, from a few tens of seconds to a day or more. We reanalyze high resolution wind data and demonstrate the fractal character of the point process generated by the wind speed level crossings. We simulate the fluctuating wind speed by a Markov process which approximates the characteristics of the real (non-Markovian) wind and successfully generates a power law distribution of episode lengths. However, fundamental questions concerning the physical basis for this behavior and the connection between the properties of a continuous-time stochastic process and the fractal statistics of the point process generated by its level crossings remain unanswered.
TL;DR: In this article, the authors attempt to find a reasonable method for estimating wind speed for given terrain roughness, through simultaneous wind observations at altitudes up to 420 m at sites with different roughnesses using two sets of Doppler sodars.
TL;DR: In this article, the effect of tropospheric wind shear on the gravity-wave generation was explored. But the results showed that the gravity waves propagate away from the cloud with wavefronts that are approximately circular, implying that convective clouds do not generate waves which propagate in a preferred direction.
Abstract: Observed wind and temperature profiles are used to initialize a model calculation of a maritime continent thunderstorm, and the numerical solution is used to explore the effect of tropospheric shear on the gravity-wave generation. The resultant convective system is qualitatively similar to that observed. The modelled gravity waves propagate away from the cloud with wave-fronts that are approximately circular, implying that the convective clouds do not generate waves which propagate in a preferred direction.
The gravity-wave generation is related to the oscillation of the convective updraughts about their level of neutral buoyancy. While the general features of the gravity waves are similar in most respects to a previous study which used an idealized wind profile, the frequency of the gravity waves is Doppler-shifted by the tropospheric wind shear. The result is a much broader power spectrum in comparison to the idealized cases.
TL;DR: In this article, a large aperture scintillometer was compared to those made using an eddy correlation system over a uniform barley field, and good agreement was found between the instruments for measuring sensible heat fluxes as long as an effective value for the displacement height was used in the equations.
TL;DR: In this article, the effects of motion-induced modal wind forces acting on a high-rise building with a side ratio of 2 during across-wind and torsional vibration were measured by a forced-vibration method in a wind tunnel.