Presentation on theme: "INVESTIGATION OF LOCAL STATISTICAL CHARACTERISTICS OF TURBULENT WIND FLOW IN ATMOSPHERE BOUNDARY LAYER WITH OBSTACLES Yuriy Nekrasov, Sergey Turbin."— Presentation transcript:
INVESTIGATION OF LOCAL STATISTICAL CHARACTERISTICS OF TURBULENT WIND FLOW IN ATMOSPHERE BOUNDARY LAYER WITH OBSTACLES Yuriy Nekrasov, Sergey Turbin
2 Introduction Atmospheric, in particular, wind, load on building designs and the objects in many respects are determined by climatic and topographic features of terrain, in which one the concrete object places. In the article the approaches to perfecting a technique of the collecting and data logging about wind flow in near-ground atmospheric boundary layer with reference to definition of actual wind characteristics near obstacles are considered. Some outcomes of turbulent near-ground parameters research of an atmospheric layer obtained by means of a mock-up sample of a specialized system of continuous monitoring meteorological parameters are submitted.
3 Experimental investigations of local characteristics of wind flow. Donbas State Academy of Civil Engineering and Architecture. NW direction – forest. SE direction – four storied buildings. During first part of measurements the thermoanemometer placed on a roof of a four-storied building (altitude of 16 meters), at the altitude 4 meters from a level of a roof.
4 Experimental investigations of local characteristics of wind flow. Novoazovsk WPS is situated on the hilly place (distance between hills near 1 km) with differences in heights close to 40 meters, has a grass 20-30 cm and lie 3-4 km from see beach. WPS is located on the hill between two comparatively deep shallow gullies. This location provides possibility of realization for different types of wind flow related with it direction.
5 Topographical map of Nowoasovsk WPS - points of wind measurements. N.N.
8 Location of wind measurement devises on towers in Novoazovsk WPS
9 Probability density distribution: a)=2.78 m/s, =0.39, L x =1329m; b)=2.30 m/s, =0.48, L x =843m; c) =2.31m/s, =0.55, L x =570 m; d) =2.66 m/s, =0,70, L x =404 m; e) =1.82m/s, =0.81, L x =206m; f)=1.91 m/s, =0.90, L x =175 m.
10 V- flow velocity, - its average value, v- dimensionless speed, - mean quadratic deviation(rejection), = / a turbulence level of a flow. The correction was entered in view of symmetry of a normal distribution, and also taking into consideration that fact, that spacing interval from point of intersection of a curve with an ordinate axis up to average value of dimensionless speed is equal 1.
11 Corrected probability density distribution function: a) =0.55, b) =0.70
12 Gusts and their power representation: а) =2.05, =0.75;b) =2.66, =0.70; c) =1.91,, =0,9
13 Integral view of wind flows on Novoazovsk WPS field
14 The diagram of signal of hot-wire anemometer. Height – 24 meters. Average velocity for 1 hour = 9,8 m/sec; level of turbulence =16%; root-mean-square of velocity =1,6 m/sec. The diagram of signal of hot-wire anemometer. Height – 10 meters. Average velocity for 1 hour = 6,0 m/sec; level of turbulence =29%; root-mean-square of velocity =1,8 m/sec. parameters of turbulence levels ( [13; 32] %) and longitudinal scale of turbulence (L x [174; 3061] m )
15 Energy spectrum of wind velocity on 24 meters height.
16 The histogram and density function of wind gusts duration Parameters of Weibull distribution and have a small scatter in a range [1.04; 1.12]; [0.54; 0.61]. Thus invariance of frequency function of gusts wind duration has been displayed related with the point of measurement.
17 The histogram and density function of non-dimensional maximums of velocity in gusts. V max - velocity average value determined on the time interval; - velocity average value determined on the time interval v max - non-dimensional maximum of the gust Probability density function of gusts wind maximums has absolutely another character. Depending of measurement points with different wind directions the parameters of distribution change in broad limits: α [1.4; 1.8], а β [2.8; 16.8].
18 Conclusions: The outcome investigations of local meteorological characteristics shows that wind flow characteristics are unpredictable. Wind flow has non-stationary and non-Gauss character. Place of measurement and wind directions have big influence on Weibull distribution for maximum wind velocity. The experimental methods are more appropriated for wind load estimation for building structures researches.