Wind Turbulence Characteristics Research Articles

Wind energy potential in compact urban areas with balconies

The rapid global development of urbanization has led to increased building densities. Wind-energy-harnessing dense building array in urban areas is a contemporary initiative to increase the share of affordable and clean energy in global energy production. This study comprehensively investigates the accuracy of computational fluid dynamics simulations for predicting mean and turbulent wind characteristics over a typical 3 × 3 building array placed in close proximity. The three-dimensional steady Reynolds-averaged Navier–Stokes and Reynolds stress model models provide the most accurate wind velocity, turbulence intensity, and wind power density predictions for a typical building array. We evaluate various impact parameters of urban building arrays, including (1) plan area density, (2) unequal building height arrangements with and without balconies, (3) balcony depth, and (4) balcony density. Based on our results, we recommend a plan area density (λp) of 0.4 as the mounting site of wind turbines due to its excellent average power density and unacceptable turbulence region. The arrangement of buildings, the presence of balconies, and balcony design significantly modify urban wind patterns. The depth of balconies from 2.5 to 10 mm will increase average wind power density by 25% at wind directions of 0°, and the difference is minimal at wind direction of 45°. Lower balcony densities are more suitable for installing wind turbines on rooftops. Furthermore, the results provide design guidelines for compact building arrays with balconies for urban planning and wind energy exploitation.

Mathematical Analysis of the Wind Field Characteristics at a Towering Peak Protruding out of a Steep Mountainside

Wind field characteristics in a complex topography are significantly influenced by the nature of the surrounding terrains. This study employs onsite measurements to investigate the wind field characteristics at a towering peak protruding out of a steep mountainside, where butterfly−lookalike landscape platform will be constructed; the impact of the surrounding topography on the wind flow is highlighted. The results showed that the blocking effect of the mountains in the mountainous side of the valley caused a significant drop in the mean wind speed from that direction. The stationary test (reverse arrangement test) indicated that the wind speed had a strong nonstationary characteristic, necessitating the employment of a steady and nonstationary wind speed model to assess the wind turbulence characteristics. The three directions’ wind turbulence integral scales were critically influenced by the occurrence of the wind speedup effect, unexpectedly resulting in the vertical turbulence integral scale being the greatest of the three. Furthermore, the measured wind turbulence properties under both wind speed models showed certain variations from the recommended specifications. Consequently, the impact of the local terrain and the speedup effect on the wind characteristics must be thoroughly evaluated to ensure the structural stability of structures installed at a similar topography.

A Novel Frequency Control Method for Smart Buildings With Wind Power System Integration Considering Turbulence Characteristics

Faced with the challenge of decarbonization, the net-zero smart building energy system with the integration of a wind power system could become one practical solution for people's energy usage, and a proper frequency control method is essential in helping realize the goal. This article studies the frequency control method of the net-zero smart building energy system adopting a wind power system where the influence of wind turbulence characteristics on the system frequency has been analyzed. The novelty lies in formulating the relationship between frequency deviation and turbulence characteristics, based on which, an innovative frequency controller has been designed where an additional reference power output is added to the traditional over-speed control to obtain a better frequency regulation performance according to turbulence characteristics. The simulations and experiments carried out on a frequency control experimental platform demonstrate the effectiveness and superiority of the improved control method.

Influence of coherent structure on turbulence characteristics of 0814 strong typhoon Hagupit

In order to explore the formation mechanism of the nonstationary wind speed in the eye wall regions and eye region of a typhoon, taking the measured data of No.0814 strong typhoon Hagupit as the research object, we identify and extract the coherent structure of the measured wind field by discrete wavelet transform combined with hypothesis testing, and analyze the influence of the coherent structure on the nonstationary and non-Gaussian wind speed and study the influence of the coherent structure on the wind turbulence characteristics. The results show that for the 0814 typhoon Hagupit process, the coherent structure is the main reason that leads to the nonstationary and non-Gaussian fluctuating winds in the typhoon field, and with the coherent structures being exacted from the original winds, the nonstationary and non-Gaussian characteristics of the nonstationary wind samples are significantly weakened. The average contribution of the coherent structure to the turbulence parameters ranges from 6.42% to 32.40%. The duration of the coherent structure is about 10.60% of the sample duration, however, its contribution to turbulent kinetic energy is up to 40.50%. The coherent structure has the characteristics of short duration and high energy content, which is the cause of the abnormally large turbulence parameter value. This study can provide a reference for the refined wind resistance design of structures under the action of nonstationary wind.

CFD evaluation of mean and turbulent wind characteristics around a high-rise building affected by its surroundings

This study comprehensively investigated the accuracy of computational fluid dynamics (CFD) simulations for predicting the mean and turbulent wind characteristics around a high-rise building surrounded by low-rise street canyons. The flow field was characterized based on the complicated interaction between a high-rise building and its surrounding buildings, which has rarely been examined in previous CFD studies. We obtained the CFD results using steady Reynolds averaged Navier-Stokes equation (RANS) models and large eddy simulations (LES), which were compared with the measurement results obtained via wind tunnel experiments. Furthermore, we quantitatively investigated the impact of the presence of a high-rise building on the prediction accuracy of pedestrian wind environments, including the gust wind velocity. The results showed that the performance of both LES and RANS decreased in the presence of a high-rise building, indicating that predicting the flow around a high-rise building is more challenging than predicting the flow of a simple street canyon. Additionally, the prediction accuracies of RANS and LES for the mean wind velocity at the pedestrian level were similar in regions with high wind velocity. However, the prediction accuracy of LES in the medium- and low-wind-velocity regions was significantly better than that of RANS, which is closely related to the superior prediction accuracy of turbulent kinetic energy in LES. Although LES can predict the gust wind velocity directly with higher accuracy than that of RANS by using a gust factor, RANS can be used to predict the gust wind velocity with a certain accuracy using a peak factor.

A Novel Computational Approach for an Improved Expression of the Spectral Content in the Lower Atmospheric Boundary Layer

The paper presents an innovative methodology for the simulation of incoming wind conditions in computational domains that use large eddy simulation (LES) for the evaluation of wind loads on low-rise buildings. Simulating the atmospheric boundary layer has proven to be a challenging process for computational wind engineering, especially to correctly introduce the fluctuations in the high-frequency spectral domain. Experiments in the Concordia University Building Aerodynamics Laboratory were carried out to estimate the evolution of turbulence features in the along-wind direction of a generic profile. Virtual probes were placed inside the computational domain to match the location of those in the wind tunnel and compare mean speed values, turbulence intensity, integral length scales, and spectral content. Synthetic methods were applied for the incoming wind velocity to estimate their capacity to capture the evolution of these turbulence features in the streamwise direction. The inability of these synthetic methods to represent the spectral domain, particularly for heights of interest for low-rise buildings, was examined, and the so-called dynamic terrain method in which velocity time histories are extracted from wind tunnel measurements and reconstructed to fit certain statistical parameters was implemented. The proposed method represents the frequency domain’s spectral content with good agreement with the theoretical von Karman spectrum and the experimental results. Advantages of the method include time efficiency and relative simplicity, which makes it attractive to the practitioners for the design of a neutral atmospheric boundary layer respecting the turbulent wind characteristics.

Performance analysis of shrouded invelox wind collector in the built environment

Shrouded wind turbines are emerging as a promising approach for integrating wind energy into residential areas. A wind turbine’s shrouding plays a key role in strengthening the wind speed in low-wind areas, thereby maximizing power generation. The wind speed is improved by various novel geometries, airfoils, and positioning of the turbines at various locations. In this research, further improvement in wind speed is attained by optimizing the shrouded profile using the Taguchi approach. A modified INVELOX is attached at the exit of the shroud for harnessing wind power at multi-stages using the shrouded turbine. A high turbulence environment at two distinct locations was chosen based on the standards of the International Wind Agency to validate the performance of the shrouded INVELOX small-scale wind turbines. The wind turbulence characteristics based on the urban atmospheric boundary layer inflow situation over the above locations are analyzed using computational fluid dynamics and validated with experimental results. The shrouded INVELOX increases the wind speed by 1.52 times the actual wind speed when located at low-rise buildings and increases by 1.68 times when located at the top of the tallest building. The shrouded INVELOX performs better in comparison with the shroud and INVELOX when operated separately.

Wind speed time series forecasting method in wind farm based on EEMD

The article described the relevant knowledge of wind speed prediction and the verification method of the forecast. First, the characteristics of wind speed are general analyzed. Through the form of wind, speed frequency of wind, shear speed and turbulence characteristics of wind, it was found that the wind speed had instability and non-linear characteristics. By analysing the basic principles of the three methods included the time series, neural network method and empirical mode decomposition, the wind speed time series prediction method was proposed. On the basis of this method, it was applied to a raw wind factory speed time series and simulated reality by Matlab. Compared the predictive conclusion with original data, it gained a higher accuracy and verified the efficiency of the method.

An Analytical Framework for the Investigation of Tropical Cyclone Wind Characteristics over Different Measurement Conditions

Wind characteristics (e.g., mean wind speed, gust factor, turbulence intensity and integral scale, etc.) are quite scattered in different measurement conditions, especially during typhoon and/or hurricane processes, which results in the structural engineer ambiguously determining the wind parameters in wind-resistant design of buildings and structures in cyclone-prone regions. In tropical cyclones (including typhoons and hurricanes), the inconsistent wind characteristics may be in part ascribed to the complex flow structure with the coexistence of both mechanical and convective turbulence in the boundary layer of tropical cyclones. Another significant contribution to the scattered wind characteristics is due to various measurement conditions (e.g., terrain exposure and height) and data processing schemes (e.g., averaging time). The removal of the inconsistency in the field-measurement system may offer a more rational comparison of measured wind data from various observation platforms, and hence facilitates a better identification scheme of the wind characteristics to guide the urban planning design and wind-resistant design of buildings and structures. In this study, an analytical framework was firstly proposed to eliminate the potential observation-related effects in wind characteristics and then the wind characteristics of seven field measured tropical cyclones (four typhoons and three hurricanes) were comparatively investigated. Specifically, field measurements of wind characteristics were converted to a standard reference station with a roughness length of 0.03 m, observation duration of 10 min for mean wind and averaging time of 3 s for gusty wind at a 10 m height. The differences of the measured wind characteristics between the typhoons and hurricanes were highlighted. The standardized turbulent wind characteristics under the analytical framework for typhoons and hurricanes were compared with the corresponding recommendations in standard of American Society of Civil Engineers (ASCE 7-10) and Architectural Institute of Japan Recommendations for Loads on Buildings (AIJ-RLB-2004).

Measurement, modeling and simulation of wind turbulence in typhoon outer region

Typhoon is one of the most destructive natural hazards, causing tremendous economic loss and fatalities every year all over the world. High-frequency wind observing tools have been deployed in many projects, which have been utilized in many recent studies to obtain data on typhoon winds, as well as turbulence. This study utilized field measurement data from the Xihoumen Bridge health monitoring system and examined the wind characteristics over water terrain at single point from four typhoons when their outer regions passed the bridge. This study firstly reviews the typhoon structure, which consists of two airflow circulations in horizontal and vertical directions. Results of this study suggest that the near ground wind turbulence characteristics should be analyzed for both directions separately. Next, the turbulence intensity, length scale, spectrum, and non-Gaussian features (skewness and kurtosis) are presented. Correlations among these parameters are also analyzed, and simplified mathematical models are introduced to quantify the correlation among various turbulence characteristics. Then, a Hermite-model based translation function method is used to simulate the non-Gaussian turbulences for different typhoon configurations. Gaussian turbulence neglecting skewness and kurtosis is also generated, and the comparison shows that non-Gaussian turbulence tends to have larger extreme gusts.

Characteristics of wind turbulence near the boundary layer in Three-North Regions of China

Based on the daily 10-minute wind observation data of the wind tower in CWERPON from 2013 to 2017, this study analysed the distribution and variation characteristics of wind turbulence in different gradients and periods in wind resource rich regions in NEC, NC and NWC. Results showed that: 1) The average wind speed from ground to 100 m height was 6.7m/s, which increased with the height, and the dominant wind speed was 4.0 m/s. The average wind speed at the height of 10 m, 30 m, 50 m, 70 m and 100 m were 6.0 m/s, 6.4 m/s, 6.7 m/s, 7.0 m/s and 7.5 m/s respectively. The highest and the lowest wind speed frequency occurred at the heights of 10m and 100m layers, which accounted for more than 22.5 % and 12.5 %. Starting from the wind speed of 6.0 m/s, the proportion of lower layers wind speed decreased, while that of high layers wind speed increased. 2) The average It decreased from low layers to high layers. Each layer’s It decreased gradually with the increasing of wind speed. The It values were different among these three regions in the study area, the NEC region was the largest, followed by the NWC, and the It value in NC stations were the smallest. Under the wind speed of 3.0-25 m/s and 15.0 m/s, the average It of each layer were 0.118 and 0.099 respectively; the maximum values were 0.189 and 0.120 at the height of 10 m in NEC region, and the minimum were 0.082 and 0.063, both of which appeared in the 100 m gradient in NC region and NWC region respectively. 3) The variation ranges of It among adjacent layers were different, the lower the layer was, the greater range of change occurred. The differences between the 10-30 m, 30-50 m, 50-70 m were 0.028, 0.013 and 0.003 respectively. 4) Each layer’s It corresponded to the variation trend of the air temperature. It increased slowly from 06:00, which reached the maximum value around 14:00, and then decreased slowly. 5) The wind turbine reach the C and B turbulence intensity level respectively at the height of 30 m and 10 m in the study area when the average wind speed is lower than 6.0 m/s, and some stations’ wind turbine type in these three regions should be at least A level.

Turbulent wind characteristics in typhoon Hagupit based on field measurements

Wind loads are the dominant loads for large-scale buildings and structures in tropical cyclone-prone regions; however, wind characteristics in tropical cyclones are still far from being understood. In this study, wind characteristics concerned in engineering applications, for example, wind attack angle, friction velocity, drag coefficient, turbulence intensity, integral scale, gust factor, and peak factor, were carefully investigated based on field measurements in typhoon Hagupit and were compared with measurements in typhoon Maemi and three hurricanes in literatures. The results show that drag coefficient increases with mean wind speeds at low levels and then decreases gradually at wind speed greater than 22.45 m/s in typhoon Hagupit over sea surface; turbulence intensities in front-side eyewall region are greater than those in back-side eyewall regions both in typhoons and hurricanes; the ratio between longitudinal integral scale and lateral integral scale, [Formula: see text], is scattered, but the ratio between longitudinal integral scale and vertical integral scale, [Formula: see text], is closer both in typhoons and hurricanes; the gust factor in typhoon Hagupit is 1.25 over open sea surface and 1.42 over open flat terrain; the peak factor is about 2.4.

Measurement of Non-Stationary Characteristics of a Landfall Typhoon at the Jiangyin Bridge Site.

The wind-sensitive long-span suspension bridge is a vital element in land transportation. Understanding the wind characteristics at the bridge site is thus of great significance to the wind- resistant analysis of such a flexible structure. In this study, a strong wind event from a landfall typhoon called Soudelor recorded at the Jiangyin Bridge site with the anemometer is taken as the research object. As inherent time-varying trends are frequently captured in typhoon events, the wind characteristics of Soudelor are analyzed in a non-stationary perspective. The time-varying mean is first extracted with the wavelet-based self-adaptive method. Then, the non-stationary turbulent wind characteristics, e.g.; turbulence intensity, gust factor, turbulence integral scale, and power spectral density, are investigated and compared with the results from the stationary analysis. The comparison highlights the importance of non-stationary considerations of typhoon events, and a transition from stationarity to non-stationarity for the analysis of wind effects. The analytical results could help enrich the database of non-stationary wind characteristics, and are expected to provide references for the wind-resistant analysis of engineering structures in similar areas.

Micrositing of roof mounting wind turbine in urban environment: CFD simulations and lidar measurements

Roof mounting wind turbine (RMWT) is a promising form of wind energy utilization in urban environment. According to the International Energy Agency wind task 27, a recommended practice on micrositing of small wind turbines in the areas of high turbulence needs to be formulated. A computational fluid dynamics (CFD) study on the wind turbulence characteristics over the Engineering and Technology Building (ETB) on campus based on the urban atmospheric boundary layer (UABL) inflow condition is conducted, and the results are validated by wind lidar measurements. The micrositing method of RMWT is developed based on the CFD simulations, which contains preliminary and accurate micrositings. Results from this investigation suggest that the optimum installation height ranges from 1.51 to 1.79 times the height of building and the best locations are at the forefront where the wind acceleration reaches the maximum, as the wind direction varies. The methods developed in this paper can provide a feasible scheme for micrositing of RMWTs in urban environment and the results can also serve as a recommendation to this topic.

Wind characteristics at Sutong Bridge site using 8-year field measurement data

Full-scale wind characteristics based on the field measurements is an essential element in structural wind engineering. Statistical analysis of the wind characteristics at Sutong Cable-stayed Bridge (SCB) site is conducted in this study with the recorded long-term wind data from structural health monitoring system (SHMS) between 2008 and 2015. Both the mean and turbulent wind characteristics and power spectra are comprehensively investigated and compared with those in the current codes of practice, such as the measured wind rose diagram, monthly maximum mean wind speed, turbulence intensity, integral length scale. Measurement results based on the monitoring data show that winds surrounding the SCB site are substantially influenced by the southeast monsoon in summer and strong northern wind in winter. The measured turbulence intensity is slightly higher than the recommended values in specifications, while the measured ratio of lateral to longitudinal turbulence intensity is slightly lower. An approximately linear relationship between the measured turbulence intensities and gust factors is obtained. The mean value of the turbulence integral length scale is smaller than that of typical typhoon events. In addition, it is found that the Kaimal spectrum is suitable to be adopted as the power spectrum for longitudinal wind component at the SCB site. This contribution would provide important wind characteristic references for the wind performance evaluation of SCB and other civil infrastructures in adjacent regions.

Wind characteristics near the ground during typhoon Meari

Wind speed and direction data during typhoon Meari were obtained from eight anemometers installed at heights of 10, 20, 30, and 40 m on a 40-m tower built in the Pudong area of Shanghai. Wind-turbulence characteristics, including wind-speed profile, turbulence integral scale, power spectra, correlations, and coherences were analyzed. Wind-speed profiles varied with time during the passage of Meari. Measured wind-speed profiles could be expressed well by both a power law and a log law. Turbulence integral scales for u, v, and w components all increased with wind speed. The ratios of the turbulence scales among the turbulence components averaged for all 10-min data were 1׃ 0.69׃0.08 at 10 m, 1׃0.61׃0.09 at 20 m, and 1׃0.65׃0.13 at 40 m. The turbulence integral scales for the u and v components increased with average gust time, but the turbulence integral scale for the w component remained almost constant when the gust duration was greater than 10 min. The decay factor of the coherence function increased slightly with wind speed, with average values for longitudinal and lateral dimensions of 14.3 and 11.3, respectively. The slope rates of the turbulence spectra in the inertial range were less than −5/3 at first, but gradually satisfied the Kolmogorov 5/3 law. The longitudinal wind-power fluctuation spectrum roughly fitted the von Karman spectrum, but slight deviations occurred in the high-frequency band for lateral and vertical wind-power fluctuation spectra.

Analysis and Simulation of Wind Turbine Optimal Control Considering wind Turbulence Characteristics

A maximum power point tracking (MPPT) algorithm of wind turbines considering wind turbulence characteristics is presented in this paper. The turbulence characteristics of natural wind are analyzed, and the natural wind speed model is established. A MPPT algorithm based on extremum-seeking control (ESC) is proposed, which considers the turbulence characteristics containing in wind speed. The goal of the MPPT algorithm is to keep the wind turbines running at the maximum wind energy utilization coefficient point stably. The algorithm is modeled and analyzed, and the simulation results show that the MPPT algorithm is correct and effective.

A comparative study of field measurements of the turbulence characteristics of typhoon and hurricane winds

Tropical cyclones are referred to as typhoons and hurricanes in the South China Sea/North Pacific and the Atlantic Ocean, respectively. As the genesis of these storms results from different basins and latitudes, the wind field characteristics may differ in these storms and differ with the recommendations in current wind codes, which are mainly based on extratropical winds. In order to delineate any differences, based on wind data measured at fixed/deployable towers in four typhoons and three hurricanes, turbulent wind characteristics, e.g., turbulence ratio and intensity, integral scale, gust factor, peak factor, skewness and kurtosis, were comparatively investigated and compared with the recommendations in ASCE7-10. In this comparison, the influences of roughness length and mean wind speed on the turbulent wind characteristics were also examined.

Near-Surface Wind Speed Fluctuation and its Impact on Wind Power in Jiuquan

With the use of representative observed wind speed data for a whole year in Jiuquan field in Gansu province of Hexi Corridor ,we analysed the characteristics of ten-minutes wind speed, diurnal wind speed, monthly wind speed variation , as well as the influence of the wind power change rate in different time periods and diurnal variation in four seasons. Studies have shown that ten-minutes short-term wind turbulence characteristics was more obvious, with some randomness , but mainly exhibited typical diurnal characteristics of variation. In addition to mean state of wind conditions, there were sustained gale, short-term gale, continued small wind, regular small wind appeared. Monthly variation of wind speed is characterized by the "three peaks and three valleys" , showing the regular change that wind speed was larger in spring and summer , and it was smaller in autumn and winter. Daily fluctuation of wind electricity generation in four seasons presented similar trends, it was a peak-valley feature, valley generally appeared between 9-11 a.m., the peak occurred between 5-7 p.m..Wind power got larger between 1 and 11 p.m., this period was the peak electricity needed, wind power added can significantly ease the power grid pressure and will has significant positive effect for the power grid control. Ten-minute power variation was relatively stable, with the time interval increased, variation in electricity generation of one day rate increased gradually.

Efficacy of Averaging Interval for Nonstationary Winds

AbstractIn comparison with atmospheric boundary-layer winds, which are generally regarded as stationary, windstorms such as hurricanes and thunderstorms/downbursts have strong nonstationary features characterized by rapid changes in wind speed and direction. The averaging interval associated with turbulent wind characteristics in boundary-layer winds is typically varied between 10 min and 1 h. A fixed averaging interval (FAI), which uses a constant mean to isolate the fluctuating wind component, has been effective in characterizing boundary-layer winds; however, the question remains as to whether the user-defined interval is appropriate for nonstationary winds. To address this concern, a variable averaging interval (VAI) scheme is proposed. For better understanding of the characteristics of nonstationary winds, traditional FAI methods are compared with alternative FAI approaches that use time-varying means and the proposed VAI approaches. In addition, the definitions for gust factor, turbulence intensity,...