Improvements in wind speed forecasts for wind power prediction purposes using Kalman filtering

This paper studies the application of Kalman filtering as a post-processing method in numerical predictions of wind speed. Two limited-area atmospheric models have been employed, with different options/capabilities of horizontal resolution, to provide wind speed forecasts. The application of Kalman filter to these data leads to the elimination of any possible systematic errors, even in the lower resolution cases, contributing further to the significant reduction of the required CPU time. The potential of this method in wind power applications is also exploited. In particular, in the case of wind power prediction, the results obtained showed a remarkable improvement in the model forecasting skill.     

风速时程AR模型及其快速实现

随着工程结构日趋多样化、大型化、复杂化，结构风振响应研究受到学术界、工程界的关注和重视，基于数值模拟方法得到的风速时程曲线在结构风振分析中被采用，自回归(AR)模型具有一系列优异性能，在时间系列分析中被广泛应用，本文基于自然风特性，通过考虑结构节点间的风速时程相关性，采用AR模型模拟节点随机脉动风速时程，并提出VC与Matlab混合编程模拟的快速实现方法．对模拟所得的网壳节点风速时程统计分析表明，AR模型可有效地模拟具有时间相关性、空间相关性的节点脉动风速时程，采用VC与Matlab混合编程快速实现方法，可较好解决模拟精度、模拟速度和计算稳定性的问题。     

Synthesis of non-Gaussian wind pressure time series on low building roofs

This paper presents an efficient and practical method for the digital generation of univariate non-Gaussian wind pressure time series on low building roofs. The method, based on the Fast Fourier Transform (FFT) approach, essentially inverts the Fourier coefficients which are a linear combination of Fourier amplitude and phase. In this study, the Fourier amplitude part is assumed to be known. The Fourier phase capable of inducing non-normality to the time series is carefully modelled and a simple stochastic model with a single parameter is suggested for its simulation. The computation of this single parameter is accomplished by minimizing the sum of the squared errors in higher order statistics such as skewness and kurtosis. The simplicity and effectiveness of this methodology have been demonstrated using several measured non-Gaussian pressure data from various low building roofs under different conditions.     

Evaluating and modelling the response of an individual to a sudden change in wind speed

The response of an individual to a sudden increase in wind velocity is important in terms of wind comfort and wind safety. This paper is concerned with the latter issue and outlines a series of physical and numerical experiments undertaken in order to evaluate the response of an individual to a sudden change in wind speed. The physical experiments were undertaken in the dynamic circuit of the Jules Verne Climatic Wind Tunnel at CSTB in Nantes, France and subjected 31 people to wind speeds up to 20 m/s. In all cases the wind speed increased from a mean value of zero to the target value in approximately 0.2 s. The wind speed required to cause loss of balance is shown to be a function of orientation and weight.     

A probability-based analysis of wind speed distribution and related structural response in southeast China

According to the Chinese Load Code, the wind load for the structural design is based on the T-year return period of the annual maximum 10-min average wind speed. Therefore, determining the accurate regional annual maximum 10-min average wind speed, distribution is extremely important and essential. In this article, a new approach named generalised unified probability plotting (GUPP) method is proposed to parametrically analyse the regional wind speed distribution. The historical data of wind speed from 1953 to 2015 at southeast coastal city Xiamen, the distribution and parameters of the average 10-min annual maximum wind speeds are obtained. From the analysis results, the annual maximum 10-min average wind speed can be best modelled by the Pearson-III distribution among several distributions examined in the study, including the Gumbel distribution which underlies the Chinese Load Code. To further determine the significance of the updated wind speed distribution (namely the Pearson III), the wind-induced pressures at different story-levels of a high-rise building in Xiamen is examined relative to the Code-recommended distribution. Results show that the wind pressures corresponding to the Chinese Load Code is much higher than those of the Pearson-III. The difference is significant and may induce unreasonably high wind loads for design. Abbreviations Gupp Generalised Unified Probability Plot; CDF: Cumulative Distribution Function; PDF: Probability Density Function; QQ Plot: Quantile-Quantile Plot; RMS: Root Mean Square; K–S: Kolmogorov–Smirnov

     

On the estimation of wind speed in urban canyons for ventilation purposes—Part 1: Coupling between the undisturbed wind speed and the canyon wind

The present paper presents a computational methodology to calculate the wind speed in canyons when there is a coupling between the undisturbed wind speed and the airflow inside the canyon. This can happen when the undisturbed wind speed above the canyon exceeds a threshold values, i.e. 4 m/sec. The proposed algorithms are presented in details. Experimental data collected through extensive monitoring in four urban canyons in Athens Greece, are used to validate the accuracy of the proposed model. A very good agreement between the experimental and the theoretical is found for most of the cases. The proposed model can be used to calculate the wind speed in canyons for natural ventilation purposes or for any other type of studies where the wind speed is required.     

A phenomenological model for the dynamic response of wind turbines to turbulent wind

To predict the average power output of a wind turbine, a response model is proposed which takes into account: (i) the delayed response to the longitudinal wind speed fluctuations; (ii) a response function of the turbine with arbitrary frequency dependence; (iii) wind fields of arbitrary turbulence intensity. In the limit of low turbulence intensity, the dynamical ansatz as proposed in 1992 by Rosen and Sheinman is reproduced. It is shown, how the response function of the turbine can be obtained from simulation experiments of a specific wind turbine. For two idealized situations the dynamic effect of fluctuating wind is estimated at turbulence intensities 0?I_u?0.5. At the special mean wind speed , the turbine response function is determined from simulation data published by Sheinman and Rosen in 1992 and 1994.     

Dynamic response and reliability analysis of tall buildings subject to wind loading

This paper explores the wind stochastic field from a new viewpoint of stochastic Fourier spectrum (SFS). The basic random parameters of the wind stochastic field, the roughness length z₀ and the mean wind velocity at 10 m height U₁₀, as well as their probability density functions (PDF), are obtained. It provides opportunities to use probability density evolution method (PDEM), which had been proved to be of high accuracy and efficiency, in computing the dynamic response and reliability of tall buildings subject to the wind loading. Principals and corresponding numerical solving algorithm of the PDEM are first presented. Then, the adopted model of the wind stochastic field is described briefly. The simulation method of the fluctuating wind velocity based on the SFS is introduced. Finally, as an example of the application of the PDEM, a 20-storey frame subject to wind loading is investigated in detail. The responses, including the mean value and the standard deviation, and the reliabilities of the frame are evaluated by the PDEM. The results demonstrate that the PDEM is applicable and efficient in the dynamic response and reliability analysis of wind-excited tall building.     

合肥电视塔TMD风振控制的时域分析

本文对合肥电视塔进行了动力特性分析 ,同时利用仿真得到的 19维脉动风压时程样本曲线 ,对塔的振动和控制分别进行了时域分析。计算结果表明 ,利用上塔楼生活和消防水箱构成调频质量阻尼器 (TMD)对合肥电视塔的风振有明显的控制作用。最优参数的TMD可使得电视塔上塔楼峰值加速度响应下降 5 4%     

Extreme value frequency analysis of wind data from Isfahan, Iran

Estimating maximum wind speed is an essential task in many fields of environmental and engineering risk analysis. This study used prevalent westerly annual maximum wind speeds for the period of 1983-1998 for East Isfahan station in Isfahan Province, Iran. The frequency analysis of AM data wind speeds obtained by averaging the wind data over some chosen averaging periods showed that extreme value Type I distribution is the best distribution for 15, 30, 60 and 120 min wind durations. The frequency and average corresponding duration were then plotted. This plot gives the average wind duration and speed for any given return period.     

实测风场风速风向耦合的三维非平稳特征研究

为了获取考虑风速风向耦合效应的实测风场非平稳特征,在获取三维脉动风速时程的过程中,采用EMD方法建立了三维脉动非平稳风速模型,并推导出了脉动风速时程表达式,进一步发展了风速时变标准差、时变湍流强度的概念。以高层建筑实测台风数据作为算例,并与平稳风速模型进行对比分析,验证了非平稳风速模型的准确性和优越性：不需要选取基本时距;时变的物理量能反映微观特征,更能反映风速的非平稳性。通过平稳度指数检验了数据分析过程的平稳性特征,结果表明：风速在频域内的平稳性指数随着频率的增大而逐渐增大;不考虑风向时,风速的平稳性指数大小是与风速的变化速率相关的;非平稳风速模型所计算的脉动风速平稳性较平稳性模型方法所分析结果有所改善。     

Effects of building aspect ratio and wind speed on air temperatures in urban-like street canyons

The objective of this study is to simulate the characteristic role of building aspect ratio (AR) and wind speed on air temperatures during different street canyon heating situations. A two-dimensional Renormalization Group (RNG) k–? turbulence model is employed to solve the Reynolds-averaged Navier–Stokes (RANS) and energy transport equations. A comparison of the results from the adopted model with those reported by similar experimental and numerical works demonstrated that the model is quite reliable when simulating temperature and wind profiles. The model is employed to predict air temperatures in idealized street canyons of aspect ratios (building-height-to-street-width ratio) of 0.5–8 with ambient wind speeds of 0.5–4 m/s. Three situations were identified for simulating diurnal heating of street canyon. It is noted that air temperatures are positively correlated with the bulk Richardson number (R_b) in most of the cases. The results show that the air temperature difference between high and low AR street canyon (Δθ_AR) was the highest during the nighttime (i.e., around 7.5 K between AR8 and AR0.5), but low or even negative during the daytime. It is also found that air temperatures rose as high as 1.3 K when ambient wind speed decreased from 4 m/s to 0.5 m/s. It is also revealed that the Δθ_AR during different diurnal situations and the nighttime and daytime air temperature difference between urban and rural areas (Urban Heat Island, UHI) closely resemble one another. Conclusively, the results of this study have highlighted the importance of street canyon AR and wind speed on urban heating.     

The wind power potential of the eastern Mediterranean region of Turkey

The wind energy potential in the eastern Mediterranean region has been investigated using hourly wind data taken from seven stations during 1992-2001 periods by the Turkish Meteorological Service. The present work suggests that in the east Mediterranean Sea coast of Turkey, wind energy sources are convenient for electricity generation. The mean power density was determined as 500 W/m² in many areas of this region at 25 m from the ground level. The most promising locations in terms of wind power generation are identified. The contours of constant wind speed and power potential could lead the private power developers to decide the locations of appropriate wind farms.     

A comparison of methods of extreme wind speed estimation

The paper presents a comparative assessment of methods for extreme value analysis of the US wind speed data using four different methods, namely Standard Gumbel, Modified Gumbel, Peaks-Over-Threshold (POT) and Method of Independent Storms (MIS). The analysis highlights the influence of methodological assumptions on the estimates of design wind speed corresponding to 50-year and 500-year return period. The results demonstrate that the MIS method leads to more stable quantile estimates than the POT method.     

WM函数在风速分形特征分析中的应用

从时域角度出发研究问题,通过数值方法,利用分形理论,采用Weierstrass-Mandelbrot函数进行了风速时程重构,模拟出尽可能接近和满足自然风特性的时程样本,从而促进风速分形特征的研究。     

车速对沥青路面结构动力响应的影响

运用三维动力有限元的方法,分析了车速对沥青路面结构的动力响应的影响规律。分析结果表明：车速对路面结构的最大竖向位移、最大垂直压应力、最大水平剪应力产生的动力响应明显,对基层底部的最大水平拉应力和最大横向拉应力产生的动力响应非常有限。     

Time series study of the impact of serious fires on fire occurrence statistics in cities of Jiangsu

In this paper, the time series method is used to analyze the effect of fire disasters and serious fires on monthly fire occurrence statistics in 10 cities from January 1997 to December 2001 in Jiangsu province. After removal of outliers in the irregular component of the original data series and seasonal adjustments, the intervention model is applied to quantify the effect of the fire disasters and serious fires on the total monthly fire statistics in the cities of Jiangsu province. The results show that the impact on monthly fires lasts for 3 months for eight cities and 2 months for two cities. Other phenomena are also detected in these 10 cities. Finally, some explanations for these phenomena are proposed.     

Prediction of wind speed for the estimation of wind turbine power output from site climatological data using artificial neural network

In this paper, the wind speeds of Noupoort in the Western Cape region of South Africa are forecasted from the site climatological data using feed forward artificial neural network (ANN) with the back propagation training method. Different architectural designs are tested with different combinations of climatological data to obtain the most suitable ANN for predicting the wind speed of the site. The predicted wind speeds are compared with the actual measured wind speeds and the results are evaluated using mean absolute error (MAE), mean absolute percentage error (MAPE), root mean square error (RMSE) and correlation coefficient (R). Some of the key results show that combination of temperature, wind direction and time of the day (TEM?+?WD?+?T) could effectively predict wind speed of Noupoort. The forecasted wind speed shows a strong agreement with the measured wind speed with R, RMSE, MAPE and MAE of 0.96, 0.56, 6.64% and 0.44, respectively.     

Influence of low-frequency wind speed fluctuations on the aeroelastic stability of suspension bridges

Starting from the standard multimode approach to the aeroelastic instability of a long span suspension bridge, that gives the critical flutter speed in the ideal case of a wind constant both in time and in space (turbulence neglected), this paper describes a procedure to evaluate in a closed form the worst effects that can ever be expected as a consequence of a turbulence with a given spectrum. To this respect, only low-frequency wind speed fluctuations strongly correlated along the span are taken into account, neglecting the beneficial effects due to a loss of coherence or to higher frequency components. This allows to obtain a flutter speed certainly safe in comparison with any realistic turbulence field. The proposed formulation is then applied to the current design of the bridge on the Messina Strait (Italy).