scholarly journals NUMERICAL SIMULATION OF WIND FLOW OVER URBAN AREA : Part 2 Variation of mean wind speed and turbulence intensity due to the density of buildings and houses

1998 ◽  
Vol 63 (513) ◽  
pp. 59-64 ◽  
Author(s):  
Takashi MARUYAMA
Keyword(s):  
Numerical Simulation ◽  
Wind Speed ◽  
Urban Area ◽  
Turbulence Intensity ◽  
Wind Flow ◽  
Mean Wind Speed

scholarly journals Climatological Features of the Weakly and Very Stably Stratified Nocturnal Boundary Layers. Part I: State Variables Containing Information about Regime Occupation

2019 ◽  
Vol 76 (11) ◽  
pp. 3455-3484 ◽  
Author(s):  
Carsten Abraham ◽  
Adam H. Monahan
Keyword(s):  
Wind Speed ◽  
Turbulence Intensity ◽  
Three Dimensional ◽  
Static Stability ◽  
Wind Component ◽  
State Variables ◽  
Intermittent Turbulence ◽  
Additional Information ◽  
State Variable ◽  
Mean Wind Speed

Abstract The atmospheric nocturnal stable boundary layer (SBL) can be classified into two distinct regimes: the weakly SBL (wSBL) with sustained turbulence and the very SBL (vSBL) with weak and intermittent turbulence. A hidden Markov model (HMM) analysis of the three-dimensional state-variable space of Reynolds-averaged mean dry static stability, mean wind speed, and wind speed shear is used to classify the SBL into these two regimes at nine different tower sites, in order to study long-term regime occupation and transition statistics. Both Reynolds-averaged mean data and measures of turbulence intensity (eddy variances) are separated in a physically meaningful way. In particular, fluctuations of the vertical wind component are found to be much smaller in the vSBL than in the wSBL. HMM analyses of these data using more than two SBL regimes do not result in robust results across measurement locations. To identify which meteorological state variables carry the information about regime occupation, the HMM analyses are repeated using different state-variable subsets. Reynolds-averaged measures of turbulence intensity (such as turbulence kinetic energy) at any observed altitude hold almost the same information as the original set, without adding any additional information. In contrast, both stratification and shear depend on surface information to capture regime transitions accurately. Use of information only in the bottom 10 m of the atmosphere is sufficient for HMM analyses to capture important information about regime occupation and transition statistics. It follows that the commonly measured 10-m wind speed is potentially a good indicator of regime occupation.

scholarly journals Spreadsheet solution for the computation of the mean wind speed and turbulence intensity profiles according to the Romanian standard

2019 ◽  
Vol 85 ◽  
pp. 03002
Author(s):  
Elena-Alexandra Chiulan ◽  
Andrei-Mugur Georgescu ◽  
Costin-Ioan Coşoiu ◽  
Anton Anton
Keyword(s):  
Wind Speed ◽  
Turbulence Intensity ◽  
Structural Design ◽  
Input Data ◽  
Wind Speed Profile ◽  
Wind Action ◽  
Design Engineers ◽  
Mean Wind Speed ◽  
Wind Characteristics ◽  
The Mean

The presented paper focuses on the computation of the mean wind speed and turbulence intensity profiles for all the cities from Romania. The calculation of both, the mean wind speed profile and the turbulence intensity profile, had as mathematical support the equations presented in the Romanian design standard for wind action CR 1-1-4/2012. The main objective of this paper was to provide a tool for the computation of the two wind action features. This method was based on creating a spreadsheet in Excel with which, in just a few seconds, a user could correctly obtain the two wind characteristics. This Excel dashboard can be used as a teaching material for students as well as input data for structural design engineers in the process of modelling and observing the behaviour of a building excited by wind action on a particular city in Romania.

scholarly journals More accurate aeroelastic wind-turbine load simulations using detailed inflow information

2018 ◽  
Author(s):  
Mads Mølgaard Pedersen ◽  
Torben Juul Larsen ◽  
Helge Aagaard Madsen ◽  
Gunner Christian Larsen
Keyword(s):  
Wind Speed ◽  
Turbulence Intensity ◽  
Atmospheric Stability ◽  
Pitot Tube ◽  
Aerodynamic Model ◽  
Mean Wind Speed ◽  
Fatigue Loads ◽  
Aeroelastic Simulations ◽  
The One ◽  
Measured Wind Speed

Abstract. In this paper, inflow information is extracted from a measurement database and used for aeroelastic simulations to investigate if using more accurate inflow descriptions improves the accuracy of the simulated fatigue loads. The inflow information is extracted from the nearby met masts and a blade-mounted five-hole pitot tube. The met masts provide measurements of the inflow at fixed positions some distance away, whereas the pitot tube measures the inflow while rotating with the rotor. The met mast measures the free-inflow velocity, but the measured turbulence may evolve on its way to the turbine, pass besides the turbine, or the mast may be in the wake of the turbine. The inflow measured by the pitot tube, on the other hand, is very representative of the wind that acts on the turbine as it is measured close to the blades and includes variations within the rotor plane. This inflow is, however, affected by the presence of the turbine, and therefore an aerodynamic model is used to estimate the free-inflow velocities that would have been at the same time and position without the presence of the turbine. The inflow information used for the simulations includes the mean wind speed and trend, the turbulence intensity, wind shear profile, atmospheric stability dependent turbulence parameters, and azimuthal variations within the rotor plane. In addition, the instantly measured wind speed is used to constrain the turbulence. It is concluded that the period-specific turbulence intensity must be included in the aeroelastic simulations to make the range of the simulated fatigue loads representative for the range of the measured fatigue loads. Furthermore, it is found that the one-to-one correspondence between the measured and simulated fatigue loads is improved considerably by using inflow characteristics extracted from the pitot tube instead of the met-mast-based sensors as input for the simulations. Finally, the use of pitot-tube wind speed to constrain the turbulence is found to decrease the variation of the simulated loads due to different turbulence realisations (seeds), such that the need for multiple simulations is reduced.

scholarly journals Characteristics of Typhoon “Fung-Wong” Near Earth Pulsation

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xiujun Li ◽  
Yongguang Li ◽  
Jianting Zhou ◽  
Qian Wang ◽  
Xu Wang
Keyword(s):  
Wind Speed ◽  
Turbulence Intensity ◽  
Wind Field ◽  
Coherence Function ◽  
Intensity Attenuation ◽  
Gust Factor ◽  
Peak Factor ◽  
Mean Wind Speed ◽  
Wind Characteristic ◽  
Empirical Curve

To study the wind field characteristics near the ground pulsation in typhoon conditions, wind field conditions in the area affected by Typhoon “Fung-Wong” were monitored using wind field instruments installed in the construction building of Wenzhou University, China. Real-time wind field data were collected during typhoons. Wind characteristic parameters such as mean wind speed, wind direction angle, turbulence intensity, gust factor, peak factor, coherence function, and autocorrelation were analyzed, and the wind field characteristics during the typhoon were summarized. The results indicated that the longitudinal and lateral turbulence intensities decreased with an increase in the mean wind speed, and there was an obvious linear relationship between them. The vertical and horizontal gust factor and peak factor decreased with an increase in mean wind speed, and the trend was more obvious in the horizontal direction. There was a significant correlation between the gust factor and the peak factor. The turbulence intensity and gust factor decreased with time, and the turbulence intensity attenuation speed increased with time. The empirical curve presented by Davenport (1961) can simulate the correlation characteristics of the fluctuating wind speed components of Typhoon Fung-Wong at some measuring points. With an increase in the time difference, the dependence of the instantaneous values at the two time points gradually decreased.

scholarly journals Aero-elastic load validation in wake conditions using nacelle-mounted lidar measurements

2020 ◽  
Author(s):  
Davide Conti ◽  
Nikolay Dimitrov ◽  
Alfredo Peña
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Turbulence Intensity ◽  
Sensor Data ◽  
Wave System ◽  
Horizontal Shear ◽  
Reference Case ◽  
Elastic Load ◽  
Lidar Measurements ◽  
Mean Wind Speed

Abstract. We propose a method for carrying out wind turbine load validation in wake conditions using measurements from forward-looking nacelle lidars. Two lidars, a pulsed and a continuous wave system, were installed on the nacelle of a 2.3 MW wind turbine operating in free-, partial- and full-wake conditions. The turbine is placed within a straight row of turbines with a spacing of 5.2 rotor diameters and wake disturbances are present for two opposite wind direction sectors. We account for wake-induced effects by means of wind field parameters commonly used as inputs for load simulations, which are reconstructed using lidar measurements. These include mean wind speed, turbulence intensity, vertical and horizontal shear, yaw error and turbulence-spectra parameters. The uncertainty and bias of aero-elastic load predictions are quantified against wind turbine on-board sensor data. We consider mast-based load assessments in free wind as a reference case and assess the uncertainty in lidar-based power and load predictions when the turbine is operating in partial- and full-wake. Compared to the reference case, the simulations in wake conditions lead to an increase of the relative error as low as 4 %. It is demonstrated that the mean wind speed, turbulence intensity and turbulence length scale have a significant impact on the predictions. Finally, the experiences from this study indicate that characterizing turbulence inside the wake as well as defining a rotor equivalent wind speed model are the most challenging aspects of load validation in wake conditions.

Effects of Trees on Wind Flow Variability and Turbulence

1990 ◽  
Vol 112 (4) ◽  
pp. 320-325
Author(s):  
D. L. Elliott ◽  
J. C. Barnard
Keyword(s):  
Surface Roughness ◽  
Wind Speed ◽  
Power Output ◽  
Flow Characteristics ◽  
Wind Flow ◽  
Considerable Decrease ◽  
Flow Variability ◽  
Mean Wind Speed ◽  
Variable Power ◽  
The Mean

This paper describes the results of a field experiment at the Goodnoe Hills, Wash. site to examine the effects of trees on wind flow variability and turbulence. Although vegetation at the site consisted primarily of grass, scattered areas of trees that penetrated the site provided an excellent opportunity to evaluate the effects of surface roughness changes on the wind flow characteristics. Wind data collected at nine towers across the site revealed that surface roughness changes in the upwind fetch caused pronounced variations in the wind flow over site. At two towers that were frequently 200 m to 300 m downwind of a grove of 10-m to 18-m trees, 20–30 percent reductions in wind speed and a factor of two to three increase in turbulence were measured at a height of 32 m. A substantial increase in the magnitude of the wind gusts, as well as a considerable decrease in the mean wind speed, was observed when a tower was downwind of the trees. Implications for a wind turbine located downwind of the trees, with a hub height near 30 m, would be reduced power output, more variable power output, more start/stop cycles, and increased stress caused by the tree-induced turbulence. The effects of the trees on the wind flow characteristics were considerably reduced at heights of 60 m and at distances greater than 500 m.

Whole Process Wind Characteristics Field Measurements of a Strong Wind

2011 ◽  
Vol 243-249 ◽  
pp. 5094-5100 ◽  
Author(s):  
Ke Yang ◽  
Wen Hai Shi ◽  
Zheng Nong Li
Keyword(s):  
Wind Speed ◽  
Turbulence Intensity ◽  
Field Measurements ◽  
Integral Length Scale ◽  
Length Scale ◽  
Strong Wind ◽  
Gust Factor ◽  
Mean Wind Speed ◽  
Wind Characteristics ◽  
The Mean

This paper presents field measurement results of boundary layer wind characteristics over typical open country during the passages of typhoon Fung-wong passed by Wenzhou in July 2008. The field data such as wind speed and wind direction were measured from two propeller anemometers placed at the height of about 30m. The measured wind data are analyzed to obtain the information on mean wind speed and direction, turbulence intensity, gust factor, turbulence integral length scale and spectra of wind speed fluctuations. The results clearly demonstrate that the turbulence intensity and gust factor of typhoon Fung-wong are larger than normal, and there is a tendency for the turbulence intensities to decrease with the increase of the mean wind speed, however, there is another tendency for the turbulence integral length scale to increase with the increase of the mean wind speed. The power spectral densities of fluctuating wind speed in longitudinal and lateral directions obtained from the measured wind speed data roughly fit with Von Karman spectra. The results presented in this paper are expected to be of use to researchers and engineers involved in design of low-rise buildings.

Boundary Layer Wind Characteristics over Urban Area

2014 ◽  
Vol 501-504 ◽  
pp. 2297-2300
Author(s):  
Lun Hai Zhi
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Urban Area ◽  
Atmospheric Turbulence ◽  
Wind Velocity ◽  
Three Dimensional ◽  
Tall Buildings ◽  
Gust Factor ◽  
Mean Wind Speed ◽  
Wind Characteristics

This paper presents statistical analysis results of wind speed and atmospheric turbulence data measured from a meteorological station in Beijing and is primarily intended to provide useful information on boundary layer wind characteristics for wind-resistant design of tall buildings and high-rise structures. Wind velocity data in longitudinal, lateral and vertical directions, which were recorded from an ultrasonic anemometer during windstorms, are analyzed and discussed. Atmospheric turbulence information such as turbulence intensity, gust factor, turbulence integral length scale and power spectral densities of the three-dimensional fluctuating wind velocity are presented and used to evaluate the adequacy of existing theoretical and empirical models. The objective of this study is to investigate the profiles of mean wind speed and atmospheric turbulence characteristics over a typical urban area.

Field Investigation and Wind-Environment Numerical Simulation of Cable-Stayed Bridge Site in the West Midlands Region

2011 ◽  
Vol 255-260 ◽  
pp. 4202-4206
Author(s):  
Yue Zhang ◽  
Mi Zhou
Keyword(s):  
Numerical Simulation ◽  
Wind Speed ◽  
Field Investigation ◽  
Wind Flow ◽  
Observation Data ◽  
Bridge Site ◽  
Wind Speed Profile ◽  
Long Span Bridges ◽  
Long Span ◽  
The One

The area of mountain ridge accounts for the most part of our country land. With the development of economic construction, more and more long span bridges have been built in the mountainous region of the western in China.. Combining live observed wind with numeric simulation, the wind characteristics on the western gap of valley areas are studied. On the one hand through the self-development processing of the bridge speed data to analyze massive wind observation data, the parameters (such as wind speed profile, turbulence intensity, power spectral density) used as the main basis for calculating wind loads are achieved. On the other hand wind flow around the bridge site as well as the environment around the mountain wind flow, wind speed field and the distribution of turbulent flow, etc is obtained by using CFD technology. Based on the results that is compared with that of numerical simulation by FLUENT, the reliability and efficiency of the program is testified. It would be provided with great theoretical significance and practical engineering value passes through the foregoing study.

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