Specific Wind Directions Research Articles

Measurements of the performance of a wind-driven ventilation terminal

This paper presents the results of the measured ventilation flow rates through a roof-mounted inflow/outflow natural ventilator and of the wind pressures measured on the terminal under real conditions. The experiments were conducted at full scale at the former Silsoe Research Institute wind engineering test site using a 6 m cubic test building, referred to as the Silsoe cube, and using a test house. Ventilation rates and free-stream wind speed were measured using ultrasonic anemometers. The nominally 800 mm × 800 mm ventilation terminal on the Silsoe cube achieved a peak ventilation rate of 0·06 m3/s per m/s wind speed although the data also indicated periods when the ventilation rate dropped to approximately zero for a specific wind direction due to the vent then being in the position of flow re-attachment following separation at the windward leading edge of the roof. This has led to better knowledge in relation to the siting of such terminals. A similar terminal monitored on the test house achieved a peak ventilation rate of nearly 0·1 m3/s per m/s wind speed. The ventilation unit proved to be an effective means of providing natural ventilation and is likely to broaden the application of natural ventilation. The results of pressure measurements on the terminal louvres and the internal pressure in the cube, coupled with the measurements of the corresponding ventilating flow rate mechanisms, provide unique data with which to establish procedures for the rational design of such terminals, which is also outlined in the paper.

Thermal behavior of curved roof buildings exposed to solar radiation and wind flow for various orientations

In this study air flow, solar radiation and heat transfer from a two dimensional curved roof with north-south and east-west faced are determined and results are compared with flat roof for the same size and orientation. Comparison are performed for their corresponding roof surface temperature, and heat flow for several roof rim angles and also for various wind flow velocities, as well as for different wind directions. Turbulence is modeled by RNG k– ε method and solar radiation distribution over the roof is determined based on an appropriate model applicable to hot arid regions of Iran. Solar radiation is calculated based on the summation of beam and diffuse radiation and ground reflected radiation. For certain inside roof temperature, over all heat transfer to the building is determined with day time for various wind flows and arc shapes and results are compared with flat roof. It was found that various wind flow condition over the vaulted roof makes substantial difference on the convection heat transfer coefficient and finally on the rate of heat transfer to the building with respect to flat roof. Based on heat transfer simulation, roof temperature, heat transfer convection coefficient and heat flow though the vault for different roof arrangement and flat roofs have been determined and advantages of specific vault orientation and wind direction are specified.

Short‐term variations in development of a recurrent toxic Alexandrium minutum–dominated dinoflagellate bloom induced by meteorological conditions1

Development of an Alexandrium minutum Halim bloom affecting a Mediterranean harbor was monitored in detail using a multidisciplinary approach. A. minutum was by far the most abundant species at and near the bloom maximum, but always coexisted with members of three additional dinoflagellate genera and prasinophytes. Bloom initiation (early February) occurred during prolonged influences of sunny weather conditions, when day length exceeded 10.5 h and water temperatures reached 10.2°C. Subsequent development toward its maximum (end of March) also relied on good weather conditions, with specific wind directions favoring accumulation of cells. Arrival of rainy weather, associated with frontal boundaries of large‐scale low‐atmospheric‐pressure systems and characterized by reduced solar irradiance (heavy cloud coverage), opposite wind directions, and enhanced wind speeds, always caused temporal declines of the bloom. These declines were attributed to dispersal or displacement of algae, but a vertical migration of A. minutum cells toward the sediment was not excluded. Delayed inflows of excess terrestrial rainwater along the inner harbor wall strongly reduced salinity and prolonged a temporal decline far beyond influences of bad weather. The associated nutrient supply favored development of the phytoplankton population but reduced the toxin production of A. minutum cells. The HPLC‐determined Gonyautoxin (GTX) 1 + 4/GTX 2 + 3 ratio strongly increased toward the bloom maximum. This ratio was influenced by nutrient status and cell density and has a potential value for monitoring developmental stages of blooms. Prolonged bad weather conditions eventually hindered continuation of bloom development, and subsequent declines of algal biomass were attributed to grazing.

Relationships between NW flow snowfall and topography in the Southern Appalachians, USA

NW flow snowfall (NWFS) events are common occurrences at higher elevations (1500 to >2000 m a.s.l.) and on windward slopes in the Southern Appalachian Mountain region of the south- eastern USA. The spatial patterns of NWFS are strongly controlled by topography, resulting in pro- nounced spatial variability. The strong topographic and low-level convective forcing, coupled with low temperatures and strong winds, increases societal impacts. This paper analyzes the relationships between NWFS and various topographic and geographic (TOPO/GEOG) variables in the Southern Appalachians. We identified NWFS events on the basis of low-level wind direction, extracted values for the TOPO/GEOG variables from Digital Elevation Models (DEMs), and developed statistical rela- tionships between NWFS and the TOPO/GEOG variables. Using a multivariate regression model and GIS techniques, we also mapped mean annual NWFS across the region. Results indicate that eleva- tion and NW exposure are most strongly correlated with NWFS; however, the strength of these rela- tionships is mediated by temperature. In the colder NWFS events, the relative importance of eleva- tion is diminished, while NW exposure and distance to a NW slope are relatively more important. Additionally, we demonstrate that multivariate regression modeling in conjunction with GIS tech- niques can be an effective way to map snowfall patterns associated with specific wind directions, particularly when a strong topographic control is evident.

Speciation of size‐resolved individual ultrafine particles in Pittsburgh, Pennsylvania

Approximately 236,000 single particle mass spectra were collected throughout the duration of the Pittsburgh Supersite experiment using the third‐generation rapid single particle mass spectrometer (RSMS‐3). The instrument was operated semicontinuously for 306 days, sampling particles with aerodynamic diameters in the range of 30–1100 nm and collecting both positive and negative ion spectra, particle size, and time of detection for each particle measured. The entire data set has been fully processed and analyzed. Spectra have been clustered into 20 distinct particle classes on the basis of the distribution of their positive ion mass peaks. Negative ion spectra were classified independently within each positive ion class. Frequency of occurrence versus particle size, month of the year, and wind direction has also been calculated for the full data set, as well as within each class. Results indicate a rich array of multicomponent ultrafine particles composed primarily of carbon and ammonium nitrate. Approximately 54% of all the particles measured fell into the carbonaceous ammonium nitrate (CAN) class. These particles were observed in all size bins and from most wind directions for the entirety of this study. Ubiquitous sources throughout the area, including vehicular emissions and secondary organic aerosol formation, are considered to be responsible for a larger fraction of these particles. In terms of particle number, metal containing aerosol dominated the remainder of the particle classes identified. These particles were rich in K+, Na+, Fe+, and Pb+ and to a lesser extent, Ga+ and Zn+. They tended to be smaller in size and were highly correlated with specific wind directions, facilitating the isolation of specific sources.

Double-layer structure in the boundary layer over the baltic sea

Double-layered structures found over the Baltic Sea are investigated using radiosoundings and lidar measurements. Situations with double-layer structures are also simulated with the regional model REMO in a realistic manner. The double layer consists of two adjacent well-mixed layers, with a sharp inversion in between.Results from radiosoundings show that the double-layer structure over the Baltic Sea mainly occurs during the autumn with thermally unstable stratification near the surface. The structure is present in about 50% of the radiosoundings performed during autumn. The presence of the double-layer structure cannot be related to any specific wind direction, wind speed or sea surface temperature.The lidar measurements give a more continuous picture of the time evolution of the double layer structure, and show that the top of the lower layer is not a rigid lid for vertical transport.Two possible explanations of the double-layer structure are given, (i) the structure is caused by ‘advection’ of land boundary-layer air over the convective marine boundary layer or, (ii) bydevelopment of Sc clouds in weak frontal zones connected to low pressure systems. Also the forming of Cu clouds is found to be important for the development of a double-layer structure.

Flow around a Complex Building: Comparisons between Experiments and a Reynolds-Averaged Navier–Stokes Approach

Abstract An experiment investigating flow around a single complex building was performed in 2000. Sonic anemometers were placed around the building, and two-dimensional wind velocities were recorded. An energy-budget and wind-measuring station was located upstream to provide stability and inflow conditions. In general, the sonic anemometers were located in a horizontal plane around the building at a height of 2.6 m above the ground. However, at the upwind wind station, two levels of the wind were measured. The resulting database can be sampled to produce mean wind fields associated with specific wind directions such as 210°, 225°, and 240°. The data are available generally and should be useful for testing computational fluid dynamical models for flow around a building. An in-house Reynolds-averaged Navier–Stokes approach was used to compare with the mean wind fields for the predominant wind directions. The numerical model assumed neutral flow and included effects from a complex array of trees in the vicinity of the building. Two kinds of comparisons are presented: 1) direct experimental versus modeled vector comparisons and 2) a numerical metric approach that focuses on wind magnitude and direction errors. The numerical evaluation generally corroborates the vector-to-vector inspection, showing reasonable agreement for the mean wind fields around the building. However, regions with special challenges for the model were identified. In particular, recirculation regions were especially difficult for the model to capture correctly. In the 240° case, there is a tendency for the model to exaggerate the turning effect in the wind caused by the effect of the building. Two different kinds of simulations were performed: 1) predictive calculations with a reasonable but not high-fidelity representation of the building's architectural complexity and 2) postexperiment calculations in which a large number of architectural features were well represented. Although qualitative evidence from inspection of the angles of the vectors in key areas such as around the southeast corner of the building indicated an improvement from the higher-fidelity representation of the building, the general numerical evaluation indicated little difference in the quality of the two solutions.

Velocity characteristics of wind patterns in Tanzania

We present results of extensive analyses of speed and direction of wind patterns in Tanzania. The following key conclusions are made from the results. Firstly, the wind speed at each station along the eastern coast of Tanzania or on off-shore islands in the Indian ocean displays two clear minima in a year, one in March and the other in the September–November period. The former minimum coincides with a complete change in wind direction from north or north-east to south or south-west, while the latter minimum coincides with a complete change in wind direction from south or south-east to north or north-east. None of the eastern coastal stations has a wind direction component that continuously persists throughout the year. Secondly, each of the inland stations either displays no pronounced minimum at all in a year or displays only one pronounced minimum in a year. The latter minimum coincides with partial changes in wind direction from a dominantly preferred/common wind direction. Interestingly, each of these (inland) stations has a specific wind direction component that persists consistently throughout the year. This implies existence of a more or less permanent wind field at constant direction over the inland, but not the coastal region of Tanzania.

Optimal routing of hazardous materials considering risk of spill

The diffusion of gases over wide areas from possible spills during transport of hazardous materials is considered when determining the least risk path through a network. Spills could occur through improper operation of vehicle or container or through a collision. Relationships for minimum risk paths are developed for these cases: specific wind directions, uniform average wind direction, maximum concentration wind directions, wind-rose averaged wind directions and speeds, and multiday routing with uncertain weather conditions. The relationships are illustrated for a full-sized urban network. This paper illustrates, how a Geographical Information System approach coupled with elementary principles of optimization theory can be used to solve such complex routing problems. The mathematics developed also reveals some consistent properties of all routing problems that are generalizable. For short trips the least risk path is invariant with the assumed wind speed, the size of spill, and the toxicity of the material. It is also invariant with the selection between uniform average wind direction and maximum risk direction criteria. A hybrid between numerical and analytical methods was adopted to reduce computation requirements which are still large but acceptable.

Full-scale measurements of wind pressures on flat roof corners

Some recent wind tunnel studies have shown that wind-induced suctions on flat-roof corner points very close to the edges are very high for specific wind directions, particularly in the presence of low parapets. Full-scale measurements have been carried out on a flat-roof experimental building, 3.3 m high, beside the football field at the Loyola Campus of Concordia University to produce comparative data with the wind tunnel test results. The exposure of the building can be classified into two categories (open country and suburban) depending on the wind direction. A roof corner panel with 12 tappings has been constructed as a separate unit and has been attached to the roof. Instrumentation for the measurement of mean pressures only was available. The anemometer has been placed on a tower about 20 m away from the building at a height of 4.7 m from the ground. The reference static pressure is measured at the ground level near the anemometer. The paper presents the experimental station and the instrumentation used for the full-scale measurements and provides details of the data obtained and their comparison with the wind-tunnel results.

Full-scale measurements of wind pressures on flat roof corners

Some recent wind tunnel studies have shown that wind-induced suctions on flat-roof corner points very close to the edges are very high for specific wind directions, particularly in the presence of low parapets. Full-scale measurements have been carried out on a flat-roof experimental building, 3.3 m high, beside the football field at the Loyola Campus of Concordia University to produce comparative data with the wind tunnel test results. The exposure of the building can be classified into two categories (open country and suburban) depending on the wind direction. A roof corner panel with 12 tappings has been constructed as a separate unit and has been attached to the roof. Instrumentation for the measurement of mean pressures only was available. The anemometer has been placed on a tower about 20 m away from the building at a height of 4.7 m from the ground. The reference static pressure is measured at the ground level near the anemometer. The paper presents the experimental station and the instrumentation used for the full-scale measurements and provides details of the data obtained and their comparison with the wind-tunnel results.

The development of blowouts in ‘de blink’, a coastal dune area near Noordwijkerhout, The Netherlands

AbstractSurface changes in six blowouts in the coastal dunes near Noordwijkerhout between s‐Gravenhage and Zandvoort were measured weekly over a period of two years at 80 erosion pin sites. Readings were correlated with wind variables derived from nearby Valkenburg airbase for the same weekly periods. The values of the wind variables is determined by the number of hours that specific average wind speeds and directions were recorded.The first part of this paper deals with the process of wind erosion. Special attention is given to the relationship between surface changes and wind speed, wind direction, season and rain. Surface changes are associated with wind speeds as low as 1.25 m/s, but net lowering, i.e. erosion, is best correlated with wind speeds between 8.75 and 10 m/s. At higher wind speed there is a tendency for the blowouts to be filled in. Winds from an easterly direction generally correlate with accumulation, whereas winds from the west correspond with accumulation at low speeds and with erosion at high speeds. Springtime and autumn are the most important seasons for blowout development. The effect of rain seems to be limited: the correlations are not improved by excluding rainy days, perhaps because wet sand will be dried rapidly by strong winds.In the next part of the paper, the response of blowouts to the erosion process is discussed. Wind erosion is dominant at the windward side because contrarily to what is often assumed the erosivity decreases as soon as the air is loaded with sand. As a result, blowouts grow southwestwards against the prevailing wind. Nevertheless, much sand is also shifted by winds from other directions. The forms of the blowouts determine in their turn the efficacy of the wind. The errosivity of the wind is most pronounced in circular blowouts, it decreases as the blowout grows in length.Finally, a model of blowout development is proposed which is controlled by width, depth and length ratios.

Observed and Predicted Great Lakes Winter Circulations

Abstract Observed mean winter currants in Lakes Ontario and Huron are compared to predictions from a homogeneous, vertically integrated, steady-state model. If specific wind directions are selected to drive this model, the observed and predicted current patterns agree. The specific wind directions were chosen to maximize each lake's wind response. The agreement suggests that there is a mean wind-driven winter circulation in the Great Lakes, and that its pattern depends upon these special wind directions. Based on these factors. winter circulations for Lakes Eire, Huron and Superior are predicted.