Research on Representative Engineering Applications of Anemometer Towers Location in Complex TopographyWind Resource Assessment

The typical location and number of anemometer towers in the assessed area are the key to the accuracy of wind resource assessment in complex topography.As calculation examples,this paper used two typical complex topography wind farms in Guangxi,Yunnan province in China.Firstly,we simulated the wind resource status of the anemometer tower in the Meteodyn WT software.Secondly,we compared the simulated wind resource with the actual measured data by the anemometer tower in the same situation.Thirdly,we analyzed the influence of anemometer tower location and quantity in the accuracy of wind resource assessment through the comparison results.The results showed that the range which the anemometer tower can represent is limited(<5 kilometers),and the prediction error more than 5%.Besides,the anemometer towers in special terrain areas(such as wind acceleration areas)cannot be used as a representative choice.The relative error of the simulated average annual wind speed by choose different number of anemometer towers is about 4%,and the grid-connected power generation more than 6%.The representative effect of anemometer towers is of crucial for improving the accuracy of wind resource assessment in engineering applications.

A new method of measuring optical turbulence of atmospheric surface layer at Antarctic Taishan Station with ultrasonic anemometer

To find the optimal location for large-aperture telescopes is a goal of astronomy. Chinese Antarctic astronomy has begun to flourish in recent years, and it is an urgent need in basic astronomical work to measure and analyze the optical turbulence spatiotemporal distribution in the Antarctic region. We analyzed turbulence data measured by a mobile atmospheric parameter measurement system from 30 December 2013 to 10 February 2014 at Antarctic Taishan Station. Because there is a discrepancy between the refractive index structure constant Cn2 measured by an ultrasonic anemometer with a single-point temperature structure function method and by micro-thermometer, a new method to measure C,2 with a temperature spectrum method is proposed herein. Through comparing long-term continuous Cn2 data derived from ultrasonic anemometer with those via the new method and micro-thermometer, trend, magnitude and measured weak turbulence of-2× 10-16m-2/3 are generally satisfactory. The reason for the discrepancy in Cn2 measurement between the ultrasonic anemometer with the old method and micro-thermometer is investigated.

Location of anemometer along Lanzhou-Xinjiang railway

Using structured mesh to discretize the calculation region, the wind velocity and pressure distribution in front of the wind barrier under different embankment heights are investigated based on the Detached Eddy Simulation(DES) with standard SpalartAllmaras(SA) model. The Reynolds number is 4.0×105 in this calculation. The region is three-dimensional. Since the wind barrier and trains are almost invariable cross-sections, only 25 m along the track is modeled. The height of embankment ranges from 1 m to 5 m and the wind barrier is 3 m high. The results show that the wind speed changes obviously before the wind barrier on the horizontal plane, which is 4.5 m high above the track. The speed of wind reduces gradually while approaching the wind barrier. It reaches the minimum value at a distance about 5 m before the wind barrier, and increases dramatically afterwards. The speed of wind at this location is linear with the speed of far field. The train aerodynamic coefficients decrease sharply with the increment of the embankment height. And they take up the monotonicity. Meanwhile, when the height increases from 3 m to 5 m, they just change slightly. It is concluded that the optimum anemometer location is nearly 5 m in front of the wind barrier.

Numerical Simulation on Floating Behavior of Buoyancy Tank Foundation of Anemometer Tower

The intact stability and damage stability of a model of an anemometer tower with buoyancy tank foundation are computed by the finite element software MOSES in this paper. The natural period of the anemometer tower is discussed through frequency domain analysis. The influence of a single factor, such as towing point position, wave height, wave direction and wave period, on towing stability is discussed through time domain analysis. At the same time, the towing stability under the condition of various combinations of many factors is analyzed based on the measured data of the target area. Computer simulation results show that the intact stability is preferable and the damage stability is sufficient under the condition of plenty of subdivisions. Within the scope of the buoyancy tank foundation,the higher the towing point position is, the better the stability is. Wave height has a great impact on the motion amplitude of buoyancy tank foundation, but the effect on the acceleration is not obvious; wave period has a great impact on the acceleration, while the effect on the motion amplitude is not obvious; following-waves towing is more conducive to safety than atry.

Anemometer Modified

A four cup commercial anemometer is modified as follows. Two cups with arms extending from the pivot are removed. The other two half spherical cups are re-placed by identical double cones, each of which is composed of two cones of different altitudes joined at the bases that are the same size. There is a stiff wire connecting the two double cones to the pivot at the midpoint so they are free to spin in the horizontal plane. They are parallel but oppositely oriented. When a fan is turned on aiming an air stream toward the double cones, they constantly rotate. Increasing the distance between the long axes of the two double cones causes the rotation rate to increase for the same setting of the fan. These results are qualitatively explained by reaction forces of a flowing fluid acting on the surfaces of solid bodies with front to back asymmetry in accord with Newton’s 3rd law (action equals reaction) published by the author earlier. Besides calibrating the modified anemometer for measuring wind speed, another practical application of the concept may be the generation of electricity by the natural winds.

Effects of Precipitation on Sonic Anemometer Measurements of Turbulent Fluxes in the Atmospheric Surface Layer

Effects caused by precipitation on the measurements of three-dimensional sonic anemometer are analyzed based on a field observational experiment conducted in Maoming, Guangdong Province, China. Obvious fluctuations induced by precipitation are observed for the outputs of sonic anemometer-derived temperature and wind velocity components. A technique of turbulence spectra and cospectra normalized in the framework of similarity theory is utilized to validate the measured variables and calculated fluxes. It is found that the sensitivity of sonic anemometer-derived temperature to precipitation is significant, compared with that of the wind velocity components. The spectra of wind velocity and cospectra of momentum flux resemble the standard universal shape with the slopes of the spectra and cospectra at the inertial subrange, following the-2/3 and-4/3 power law, respectively, even under the condition of heavy rain. Contaminated by precipitation, however, the spectra of temperature and cospectra of sensible heat flux do not exhibit a universal shape and have obvious frequency loss at the inertial subrange. From the physical structure and working principle of sonic anemometer, a possible explanation is proposed to describe this difference, which is found to be related to the variations of precipitation particles. Corrections for errors of sonic anemometer-derived temperature under precipitation is needed, which is still under exploration.

DATA PROCESSING ON LINEARIZATION OF HOT-WIRE ANEMOMETER

A method of data processing to determine the coefficients of linearization equations for 1050 anemometer (produced by Thermo-Systems Inc. -TSI, USA) with the sensors made of domestic hot wire using the program preferred in this Paper is described. By calculation and test, it is indicated that the error resulting from this method is about 0. 5% of the full scale and less than TSl's. By using this method we can set up the calibration curve according to the measurement range and the diameter of the hot wire at a certain accuracy.

An Adaptive Response Compensation Technique for the Constant-Current Hot-Wire Anemometer

An adaptive response compensation technique has been proposed to compensate for the response lag of the constant-current hot-wire anemometer (CCA) by taking advantage of digital signal processing technology. First, we have developed a simple response compensation scheme based on a precise theoretical expression for the frequency response of the CCA (Kaifuku et al. 2010, 2011), and verified its effectiveness experimentally for hot-wires of 5 μm, 10 μm and 20 μm in diameter. Then, another novel technique based on a two-sensor probe technique—originally developed for the response compensation of fine-wire thermocouples (Tagawa and Ohta 1997;Tagawa et al. 1998)—has been proposed for estimating thermal time-constants of hot-wires to realize the in-situ response compensation of the CCA. To demonstrate the usefulness of the CCA, we have applied the response compensation schemes to multipoint velocity measure- ment of a turbulent wake flow formed behind a circular cylinder by using a CCA probe consisting of 16 hot-wires, which were driven simultaneously by a very simple constant-current circuit. As a result, the proposed response compensation techniques for the CCA work quite successfully and are capable of improving the response speed of the CCA to obtain reliable measurements comparable to those by the commercially-available constant-temperature hot-wire anemometer (CTA).

Development of Verification Device for Starting Lever Pressing Automation of DEM6 Portable Three-cup Anemometer

At present,the verification system of wind speed in national 3MS provincial automatic weather station has been automated,but the wind speed verification of the DEM6 portable three-cup anemometer by the straight road wind tunnel cannot be automated.In order to record the reading of this verification,it is necessary to manually move the starting lever at the wind speed field during each verification.For this problem,a set of verification device for the DEM6 portable three-cup anemometer is developed based on automatic verification system of wind speed in the 3MS provincial automatic weather station.This device uses the the driving board of starting anemometer to connect with the pressing starting lever by a bar-shaped gap,so as to realize the remote control of the starting lever.It is convenient to use,and measure multiple sets of data at the same place.The measuring results are more accurate,thereby realizing automatic pressing of wind speed starting lever.

Anemometer Modified II

A commercial anemometer was modified by replacing the four cups with four identical two-dimensional blades, each with a circular arc side and a flat side. The flat sides are fixed to four arms radiating from a pivot so that they are parallel to the wind direction. The rounded sides all point in the same direction around a circle. When the wind blows, there is a lift force on the rounded side of each blade and they unite in causing rotation about the pivot with the curved sides leading. The more blades the faster the rotation is a prediction.

Sensitivity-Enhanced Hot-Wire Anemometer by Using Cladding-Etched Fiber Bragg Grating

A sensitivity-enhanced hot-wire anemometer based on a cladding-etched optical fiber Bragg grating(FBG)coated with a layer of silver film and optically heated by using a 1480nm laser diode is demonstrated.The silver film absorbs the laser power to heat the FBG to a certain high temperature and the airflow cools down the FBG hot-wire with the cooling effect and hence the Bragg wavelength of the FBG is determined by the airflow velocity.Experimental measurement results show that the heating efficiency of the FBG hot wire is improved by 3.8times in magnitude by etching the fiber cladding from 125μm down to 73.4μm,and the achieved airflow velocity sensitivities,under a laser power of 200mW,are–3180pm/(m/s),–889pm/(m/s),–268pm/(m/s),and–8.7pm/(m/s)at different airflow velocities of 0.1m/s,0.5m/s,1.5m/s,and 17m/s,respectively.In comparison,the sensitivities are only–2193 pm/(m/s),–567 pm/(m/s),–161 pm/(m/s),and–4.9pm/(m/s)for the reference anemometer without cladding etching even at a much higher heating laser power of 530mW.These results prove that the method by using a cladding-etched FBG to improve sensitivity of FBG-based hot-wire anemometers works and the sensitivity is improved significantly.

Performance of a vehicle-mounted anemometer under cross wind: Simulation and experiment

Environmental wind measurements are essential for ensuring the operational safety of rail vehicles.In our previous work,al anemometer that can be mounted on the top of a train to achieve real-time measurements of wind speed and direction was proposed based on the pressure distributions around the cylindrical anemometer.However,the flow field on the top of the train is significantly influenced by the train;thus,the measured data might differ from the actual environmental wind parameters,particularly when trains are subjected to windbreak walls.In this study,simulations considering flow fields around trains installed with the proposed anemometer were conducted,and an improved delayed detached eddy simulation approach was adopted.Through simulations,the flow feld at the top of the train was analysed,and the aerodynamic characteristics of the anemometer were investigated.Accord-ingly,relationships between the measured wind characteristics and environmental wind characteristics are presented under various situations herein.Field experiments were performed for the proposed anemometer installed on a certain type of high-speed train along the Nanjiang Railway in China.The results obtained from both the numerical and experimental studies show that the proposed method has high accuracy for measuring environmental wind speed and direction when mounted on the top of a train.

Measurement errors and correction of the UAT-2 ultrasonic anemometer

Two kinds of measurement errors have been observed in the recently developed UAT-2 ultrasonic anemometer.One is the flow distortion produced by a"blocking effect",and the other is the angle of attack caused by the vertical misalignment of the instrument.Here,we study these errors and discuss the possible correction methods.Via a wind tunnel experiment and numerical simulation,a 3D calibration matrix was developed to correct the"blocking effect".In the field test,the angle of attack was detected by an inclinometer settled on the reference plane of the anemometer,and the instrumental misalignment or tilt was corrected by a coordinate transformation.The combined use of an inclinometer and the proposed correction method may help find a new approach for vertical velocity correction.

MEASUREMENT AND VISUALIZATION OF FLOW FIELD IN AXIAL FLOW FAN

An experimental investigation associated with the basic fluid mechanics in an axial flow fan is described in this paper. The flow field in the tip region has been studied by laser Doppler anemometer (LDA) and flow visualization technique. Some experimental data and images are interpreted to understand the complex interactions between the annulus wall boundary layer and the leakage flow. It shows that the vortex inside the blade passage is produced by the separation of annulus wall boundary layer rather than the rolling up of leakage flow.

Laser Doppler Vibrometer Without Directional Ambiguity Using Rectangular Phase Grating

The two-phase detection method for directional discrimination in laser Doppler measurements is discussed.The diffraction efficiency of a sin- gle period rectangular phase grating is analysed and a kind of back-scattered laser Doppler vibrometer without directional ambiguity using the single peri- od rectangular phase grating as the beam-combiner described.The principles of this kind of vibrometer are explained in detail,and some experimental re- sults are given.In this kind of vibrometer,the rectangular phase grating, without the zero diffracted order and even orders,is used to eliminate use- less stray light and to combine the useful signal light.Differential electronics is employed to reject signal noise.Therefore,the signal-to-noise ratio of Doppler signals and the measurement accuracy of the instrument are im- proved and the range of application is expanded.

Analysis of atmospheric turbulence in the upper layers of sea fog

Atmospheric turbulence plays a vital role in the formation and dissipation of fog. However,studies of such turbulence are typically limited to observations with ultrasonic anemometers less than 100 m above ground. Thus,the turbulence characteristics of upper fog layers are poorly known. In this paper,we present 4-layers of data,measured by ultrasonic anemometers on a wind tower about 400 m above the sea surface; we use these data to characterize atmospheric turbulence atop a heavy sea fog. Large differences in turbulence during the sea fog episode were recorded. Results showed that the kinetic energy,momentum flux,and sensible heat flux of turbulence increased rapidly during the onset of fog. After onset,high turbulence was observed within the uppermost fog layer. As long as this turbulence did not exceed a critical threshold,it was crucial to enhancing the cooling rate,and maintaining the fog. Vertical momentum flux and sensible heat flux generated by this turbulence weakened wind speed and decreased air temperature during the fog. Towards the end of the fog episode,the vertical distribution of sensible heat flux reversed,contributing to a downward momentum flux in all upper layers. Spatial and temporal scales of the turbulence eddy were greater before and after the fog,than during the fog episode. Turbulence energy was greatest in upper levels,around 430 m and 450 m above mean sea level(AMSL),than in lower levels of the fog(390 m and 410 m AMSL); turbulence energy peaked along the mean wind direction. Our results show that the status of turbulence was complicated within the fog; turbulence caused fluxes of momentum and sensible heat atop the fog layer,affecting the underlying fog by decreasing or increasing average wind speed,as well as promoting or demoting air temperature stratification.

Wavelet Transform of Velocity-Time Data for the Analysis of Turbulent Structures in a Trayed Bubble Column

Hydrodynamic and turbulent structures in the trayed bubble column with 1.2 m inner diameter have been characterized from liquid-phase velocity-time series data obtained by the hot-film anemometer. Wavelet transform analysis was used for denoising the measured data and also for evaluating quantifiers of turbulence, viz., local intermittency measure, intermittency index and flatness factor. These quantifiers help in detecting the passage of bubbles and reveal the hidden structures and patterns in data. Also, the wavelet scalewise analysis of the turbulence at various locations in the column and under different operating conditions could be used to build a direct relationship between the local gas holdup and flatness factor. The methodology is therefore suitable for online evaluation of the trayed bubble column performance and shows promise for developing strategies for improving process performance.

A mobile polar atmospheric parameter measurement system:Ⅱ. First atmospheric turbulence observation at Antarctic Taishan Station

This is the second paper of a series devoted to atmospheric optical turbulence Cn^2 observation using a mobile polar atmospheric parameter measurement system. We present the initial results of Cn^2 measurement at Antarctic Taishan Station using micro-thermal sensors and a three-dimensional sonic anemometer at height -2.0 m above the snow surface. The site testing experiments were carried out during the 30th Chinese National Antarctic Research Expedition （CH1NARE）. We collected about 1 000 h of data between 30 December 2013 and 10 February 2014. The C,： curve exhibits clear daily structures, with two peaks around midnight and midday and two troughs around 7：30 and 17：00 local time （UTC＋5）. The mean C,2 is 2.7×10^-15 m^-2/3 and the 25th and 75th percentiles of the C,2 cumulative distribution are 9.6×10^-16 m^-2/3 and 6.2×10^-15 m^-2/3, respectively. Meteorological parameters such as temperature, relative humidity, wind speed, and air pressure are also presented.

Analysis of Wind Power Assessment Based on the WRF Model

Assessing wind energy is a key step in selecting a site for a wind farm. The accuracy of the assessment is essential for the future operation of the wind farm. There are two main methods for assessing wind power: one is based on observational data and the other relies on mesoscale numerical weather prediction(NWP). In this study, the wind power of the Liaoning coastal wind farm was evaluated using observations from an anemometer tower and simulations by the Weather Research and Forecasting(WRF) model, to see whether the WRF model can produce a valid assessment of the wind power and whether the downscaling process can provide a better evaluation. The paper presents long-term wind data analysis in terms of annual, seasonal, and diurnal variations at the wind farm, which is located on the east coast of Liaoning Province. The results showed that, in spring and summer, the wind speed, wind direction, wind power density, and other main indicators were consistent between the two methods. However, the values of these parameters from the WRF model were significantly higher than the observations from the anemometer tower. Therefore, the causes of the differences between the two methods were further analyzed. There was much more deviation in the original material, National Centers for Environmental Prediction(NCEP) final(FNL) Operational Global Analysis data, in autumn and winter than in spring and summer. As the region is vulnerable to cold-air outbreaks and windy weather in autumn and winter, and the model usually forecasted stronger high or low systems with a longer duration, the predicted wind speed from the WRF model was too large.

Experimental Studies of the Effect of Wall Roughness on Particle Behavior in Gas-Particle Flows

The effect of wall roughness on particle behavior in two-phase flows in a horizontal backward-facing step is studied using a phase-Doppler particle anemometer. The results show that the wall roughness widens the particle velocity probability density distribution, enhances the redistribution of particle velocity into different directions, reduces the particle longitudinal mean velocity and increases the longitudinal and transverse fluctuation velocities and Reynolds shear stress. The effect of roughness on particle motion in the recirculation zone is weaker than that in the fully developed flow region. The effect of roughness for small particles is restricted only in the near-wall region, while that for large particles diffuses to the whole flow field.