Automatic gust recording using a commodore pet computer

A cheap (£425) computer has been used to monitor the wind speeds over a house on which special roof components are being tested.Minor modifications to a standard Munro Mk IV cup anemometer and direction vane provide a direct interface to the Commodore PET computer which waits for a 1-s gust above 20 m s^?1. The mean wind speed and direction are then stored on a tape cassette with the maximum gust speed for that hour, and for 1000 subsequent hours in which gusts above 20 m s^?1 occur.A display can be switched on at any time to show the current wind speed, the last peak, date, time, etc. A battery back-up will keep the machine operational for short periods of no mains power.Particular points of interest are the machine code frequency-sampling technique, the continuous averaging of wind speed, and the method of vector-averaging the 4-bit direction data to give an estimated direction accuracy better than ±5°.     

Atmospheric turbulence with respect to moving ground vehicles

A random-process model is developed for the turbulent wind with respect to a moving ground vehicle. The spatial and temporal variations of the wind turbulence component normal to the direction of motion of the vehicle are considered, and numerical results are given for the power spectral density, cross-correlation, square-root coherence and phase-lag functions.The power spectral density and aerodynamic-admittance functions of side force are evaluated, on the basis of a linear relationship between unsteady side force and turbulence velocity. A numerical example shows that significant excitation of vehicle suspension modes ($\text{f}{}_{\mathrm{n}}\text{\$}\text{?}\text{1}\text{Hz}$) may occur for vehicle speeds exceeding 40 m s^?1, the turbulence energy increasing approximately with the square of mean wind speed.The model gives valuable insight into the structure of turbulent wind with respect to moving vehicles, and should facilitate the interpretation of experimental data. The results also aid rational design of suspension systems for high-speed ground vehicles, to cope with loads due to wind turbulence.     

Advance measurement of gusts by laser anemometry

A coherent laser radar (or Doppler lidar) operating at a wavelength of 1.55 μm has been mounted on the nacelle of a 2.3 MW wind turbine in order to measure the wind speed in front of the blades at ranges up to 200 m. The lidar measures the component of wind speed along its beam direction but, since it rotates with the nacelle to point into the wind, this component normally differs negligibly from the actual wind speed. As an example to demonstrate the lidar's capabilities, we present samples of wind data gathered over an 18 h period in March 2003, illustrating the development of gusts that appears to be associated with the onset of solar ground heating. Wind speeds over the full period lay in the range 4-10 m s⁻¹, and the gusts were evident as a near-discontinuity in wind speed typically of order 1-2 m s⁻¹, but reaching values larger than 3 m s⁻¹. The typical timescale between gusts was of order 1 min. Improvements to this experiment are proposed that will provide more detailed information on spatial and temporal structure of such gusts.     

A new wind tunnel for industrial aerodynamics

A new wind tunnel of closed return configuration designed specifically for industrial aerodynamic testing is described and its performance is discussed. It has a working section 3 m wide × 1.5 m high × 8.1 m long with a maximum empty tunnel wind speed of 26 m s^?1 provided by its 57 kW variable speed electric motor. Various devices to generate simulated atmospheric shear flows can be fitted at the upstream end of the working section. Full-depth atmospheric boundary layer simulations at $\text{1}\text{450}$ scale have been achieved and part-depth simulations at $\text{1}\text{200}$ scale or $\text{1}\text{4}$ scale motor car model tests are practical in this tunnel.The tunnel is of simple design and construction, and was built at a cost of approximately £16 000 at 1972–1973 U.K. prices.     

The accuracy of mountain-top winds estimated from free air data

Wind measurements made on 122 m towers on mountain tops in New Zealand have been compared with data for the same times obtained from radar wind flights for the 900 m level at the nearest stations. There is clear evidence of speed-up effects caused by the mountains but these are masked to some extent by randomness in the correlations of the winds. The observed relations are simulated by reducing the 900 m mean speeds to 122 m over flat land then increasing them by the calculated speed-ups. The mixing between direction caused by randomness in the relations has also been modelled. Errors between the observed and calculated winds appear to be of the order of 1 m s⁻¹ and are not much different if the last effect is neglected. The method has potential for making useful predictions of mean speeds on mountain-tops without anemometers.     

A new boundary-layer wind tunnel at the Danish Maritime Institute

The paper describes a new boundary-layer wind tunnel at the Danish Maritime Institute in Lyngby. The wind tunnel is of the open-circuit type and is integrated into a building raised for the purpose. The design was constrained by the need to provide a simulation of the atmospheric boundary layer (without thermal stratification) and alternatively a uniform flow without excessive turbulence.The wind tunnel has a working section of principal dimensions: length 20.8 m, width 2.6 m and height 1.8 m (adjustable from 1.8 to 2.3 m). The maximum wind speed in the working section when empty is about 26 m s^?1.Data acquisition, analysis and instrumentation in relation to the new wind tunnel are discussed and, finally, an example of a simulated natural wind is presented.     

Directional persistence of low wind speed observations

Low wind speed data is presented for stable, high-pressure sunny weather for an urban environment in the UK. In these climatologies, ventilation of buildings and dispersal of pollutants is often considered inadequate. Persistence, the length of time in which the wind blows in a specific direction and for a given angular range, is analysed. The observational data shows that in these low wind speed conditions, the wind blows in a consistent direction, for significant periods of time, and that truly calm conditions are very infrequent. The analysis of data for hot, dry, sunny and high-pressure conditions at one UK urban site, indicates that there are larger than expected air movements in these light wind scenarios. Values for mean duration of persistent wind episodes commonly exceed 30 s, with similar values for the standard deviations. The Weibull statistical structure equally applies to these low wind speed observations. In this urban environment, for 45% of the time, the persistent wind events last longer than one standard deviation above the mean. At wind speeds lower than 2 m s⁻¹, the duration of persistent wind episodes remains constant and nor does it decrease with wind speed. This may be due to larger scale meteorological influences, perhaps convective activity and eddies in the boundary layer, which create air motions in calm daytime conditions in the UK.     

The boundary layer tv-2 wind tunnel of the UFRGS

A new wind tunnel of closed-return configuration has been built at the Universidade Federal do Rio Gramde do Sul, designed specifically to provide a testing facility for architectural and industrial aerodynamics. It has a main working section 1.30 m wide × 0.90 m high × 9.32 m long, with a maximum empty-tunnel wind velocity of 42 ms^?1 provided by its 100 Hp propeller.Various devices to generate simulated atmospheric shear flows can be fitted at the upstream end of the main working section, in addition to roughness elements on the floor and a set of cross-jets having a velocity up to 100 m s^?1. The empty tunnel provides a steady uniform flow with an average turbulence level less than 0.5% out of the boundary layers at the first turntable cross-section.Four turntables permit studies of wind effects for several model conditions and flow requirements.     

High resolution numerical simulation of sulphur-dioxide emission from a power plant building

Most sulphur-dioxide (SO₂) emission calculations have been performed on an annual basis and do not take into account spatial and temporal variations on fine scale. The main objective of this study is to illustrate spatio-temporal variation of SO₂ emission pattern using computational fluid dynamic (CFD) tools of the area surrounding the Yatagan Power Plant (YPP) building in Mugla, Turkey. In order to simulate the atmospheric conditions, wind speed, wind direction and the emission of SO₂ from 3 stacks of YPP including the simplified model of the power plant building, a commercial CFD, FLUENT is used. The results involve 75 km² areas surrounding the YPP with a fine mesh resolution of 5 m × 5 m. SO₂ emission shows that the CFD tool is able to simulate the emission with fine mesh digital elevation model (DEM). The DEM highly influences the local magnitude and direction of the wind in the domain which effects both spatial and temporal emission distribution of the SO₂ gases. It is noted that the hills around the YPP cause the flue gas emissions to move away from the ground for 4 main wind directions when compared with the constant elevation model.     

风暴移动对下击暴流风场特性的影响研究

气象观测表明,下击暴流的风暴中心是移动的,风暴的移动会对风场特征产生重要影响。为研究风暴移动对下击暴流风场特性的影响,基于计算流体动力学方法建立考虑移动效应的下击暴流数值模型,并通过可移动喷口的冲击射流试验对数值模拟结果进行了验证。结果表明：移动下击暴流风场在风暴中心前缘存在较大环涡,形成弓形分布的极值风速区域,最大水平风速出现在距离风暴中心r=1.0Djet（Djet为喷口直径）左右,极值风速可达1.5Vjet（Vjet为射流速度）;风暴后方水平风速被减弱,最大风速出现在r=1.5Djet附近,极值风速约为0.8Vjet。近地面竖向风速随高度的增大而增大,受风暴移动的影响,在风暴中心区域,竖向风速向风暴移动方向一侧倾斜;在风暴中心区域以外,竖向风速主要由环涡引起,较大竖向风速主要分布于风暴中心后方以及风暴中心前方1.0Djet~2.0Djet的区域。风暴的移动导致风场中测点风速和风向随时间变化显著。     

Influence des panaches ionisés sur le champ électrique terrestre

Several months of measurements of atmospheric electrical parameters, in particular of the earth's electric-field, using a mobile laboratory, have made possible an extension of previously obtained results (Laurent and Peyrous, 1979) to the industrial area of Pardies-Nogueres.This study confirms the presence of a negatively charged aerosol in the plume emitted by factory chimneys. Down-wind, under the chimney plume, the earth's electric field is inverted and takes on large negative values and, if fall-out occurs, the space charge density due to large ions becomes negative.In the first theoretical part of our paper, we reduce the chimney plume to an equivalent charged line whose charge varies with distance as a result of recombination and diffusion. Atmospheric turbulence is neglected, and only the vertical component of the electric field is measured.By mapping charts (Fig. 5) which give cross-sections of the electric field measured along-lines perpendicular to the wind direction one measures the distance (OP) between the inversion maximum (O) and the beginning of the inversion (P) and one can thus calculate the height of the chimney plume (equations (11), (12) and (13)). Then, using equation (6), and knowing the wind speed and the distance from the source one can calculate the charge. Furthermore, if the width of the chimney plume is assumed to be the same as that of the inversion indicated on the chart, and knowing the original diameter of the plume, one can calculate the mobility k of the negative particles by using the relationship indicated by Jones and Hutchinson (1976) (equation (16)).The experimental results were obtained by using a Field Mill installed on the roof of the laboratory van with the recording synchronized to the vehicle speed (Fig. 6, 7 and 8). Two sites were studied: the Lacq gas treatment plant and a plant producing aluminium by electrolysis from molten alumina at Nogueres.The distance over which the chimney plume can be localized depends on the plume charge and the wind speed. From the measurements made, it was estimated that the recombination coefficient of positive and negative charges was 6.8 m^?3 s^?1 and the mobility of negative ions in the chimney plume was 5 · 10^?5 m² v^?1 s^?1.Our calculations of the height of the chimney plume correspond well with the increase in height of the plume above the chimney outlet given by the HOLLAND formula. The measurements made on the fixed site of Lacq (Fig. 14) show the effect of wind and the relationship between the chimney plume and the electric charge.The measurements of the earth's vertical electric field to detect chimney plumes permits the localization of charged aerosols and the calculation of the charge and its altitude. It also allows one to follow the plume and, with space charge measurements, to determine where fall-out occurs. A study of the mechanism of charge separation at the source together with that of diffusion and recombination can be envisaged.A comparison between calculations using diffusion theory and results obtained from our measurements of the height of the plume is underway.     

Wind structure in a rural atmospheric boundary layer near the ground

This paper describes mean velocity, turbulence intensity, Reynolds stresses and co-spectra measured during field experiments. The data were obtained using orthogonal arrays of propeller anemometers mounted on a 20 m tower. Data were recorded only when the wind speed was ～ 10 m s^?1 or higher, and the boundary layer was therefore assumed to be neutrally stable.Values of ?_uw (0) calculated both by the eddy correlation technique and from the velocity profile were found to agree well, and also to agree well with values suggested in the literature review of Counihan [1].     

A laboratory experiment of shear-induced natural ventilation

When the wind direction is parallel to the opening façade, the wind shear near the building opening generates turbulence and entrains air across the opening. This kind of shear-induced ventilation cannot be predicted by the orifice equation because the time-averaged pressure difference across the opening is close to zero. This study uses wind tunnel experiments and the tracer gas decay method to investigate the ventilation rate of shear-induced ventilation. The influences of opening area A, external wind speed U and wind direction on the ventilation rates Q, of single-sided and two-sided openings are systemically examined. The experimental results indicate that the dimensionless ventilation rate, Q^* = Q/UA, of shear-induced ventilation is independent of the wind speed and opening area, and the value of Q^* of two-sided openings is larger than that of a single-sided opening. In addition, a cosine law was used to predict the ventilation rate of building with two-sided openings under various wind directions, and the results are compared with the prediction of the multizone ventilation model COMIS.     

The effect of slopes on sand transport — numerical modelling

Most aeolian sediment transport models and experiments have been conducted on flat horizontal surfaces. Very little numerical or analytical research has been carried out for aeolian sand transport on slopes. The current work presents numerical modelling of saltating sand for a climbing dune which has a slope angle of 20 °. The model utilised wind fields predicted from the FAA complex terrain model for two dimensional escarpment and field data and wind-tunnel measurements for flow over a scaled model. Results suggest that only particles smaller than 0.230 mm are able to climb this slope under a wind shear velocity of 30 cm s⁻¹. The field observations and measurements confirm the numerical results.     

Survey of pedestrian movement and development of a crowd dynamics model

A survey of crowd movement was recently performed at the main railway station in Wuhan City, China during the traditional Chinese spring festival in 2003. The crowd was formed by passengers in the exit tunnel of the station after getting off a train. The observed maximum density of the crowd and maximum speed of the fastest individual were 2.8 persons/m² and 1.5 m/s, respectively. The observed crowd movement speed and flow were used to determine values of the key parameters for a crowd dynamics model previously proposed by the authors. The crowd dynamics model is based on simulating the global movement of each individual under the influence of the surrounding crowd. The crowd dynamics model suggests that the crowd movement speed is dominated by two factors: (1) the front–back inter-person effect and (2) the pedestrian's self-driving motivation. The first effect gives a logarithmic relationship between the crowd speed and crowd density. The second factor depends on the individual's motivation, which is driven by people trying to divorce themselves from the control of the crowd movement. The observations and prediction model are useful tools to guide the design of public traffic systems for effective crowd dispersal.     

Mercury removal from wastewater using porous cellulose carrier modified with polyethyleneimine

An adsorbent for heavy metal was synthesized by introducing polyethyleneimine (PEI) into porous cellulose carriers. Evaluations of synthesis results and adsorbent properties were conducted. Elementary analysis of the adsorbent revealed extensive crosslinking of PEI with the modified matrix. Batch adsorption tests showed the ability of cell-PEI to selectively remove mercury even at acidic regions. At low concentration ranges, mercury adsorption by cell-PEI can be interpreted by the Langmuir isotherm. With this model, an adsorbent capacity and Hg-ligand stability constant of approximately 288.0 mg g⁻¹ and 12.91 mg⁻¹, respectively, were obtained. From adsorption rate experiments, diffusivity of Hg in the carrier was found to be approximately equal to 7.30 × 10⁻¹⁴ m² s⁻¹. Extensive crosslinking of PEI chains that restricts ligand mobility was cited as the foremost factor contributing to these observed properties.     

Wind tunnel tests on compartment fires with crossflow ventilation

When a fire occurs in a room at ground level or a compartment located in the higher floors of a very tall building , the strong ambient wind will play an important role in fire spreading and smoke movement behavior. However, wind effect on compartment fire in cross ventilation condition has not been fully studied so far. In the present study, an effort has been made to study the wind effect on compartment fire in cross ventilation condition through experimental investigations. The experimental fire was generated by 250 ml n-heptane on the floor center of a cube enclosure with two opposite vents on the walls. The inside and outside gas temperature profiles at different vertical and horizontal locations were recorded by two thermocouple matrixes. The ambient wind velocity was set to 0, 1.5 and 3 m s⁻¹. It is observed that the ambient wind would enhance the fire severity by increasing the compartment fire temperature and reducing the time to flashover. The spilled-out flame/plume would extend horizontally farther with the increase of wind speed. Simple theoretical analysis shows that there is a critical wind velocity, or a dimensional number, to differentiate whether the gas flow across the vents is bidirectional or unidirectional, which is believed to influence enclosure fire behavior greatly.     

Wind effects on smoke motion and temperature of ventilation-controlled fire in a two-vent compartment

High-rise building fire is often influenced by the ambient wind. Study concerning fire behavior in the compartment of high-rise buildings in wind environment is needed for exploring some effective methods used for evaluation of compartment fire smoke movement and control. In this paper, smoke flowing direction and temperature of ventilation-controlled fire in a two-vent compartment are studied when ambient wind blows to the vent at higher altitude. It is found that there is a critical wind speed, above which the direction of smoke movement is dominated by wind rather than by buoyancy. It is also found that ambient wind has a complex influence on smoke temperature in the compartment. When wind speed exceeds another critical value, only one steady state appears in the smoke temperature rising curve. Otherwise three steady states appear. Heat transfer through the compartment walls has great influence on the second critical wind speed.