Leighton Cochran

Full- and model-scale cladding pressures on the Texas Tech University experimental building

Abstract Extensive pressure data have been collected on a 1:100 and 1:50 model of the Texas Tech University (TTU) experimental building in a wind-tunnel simulated Atmospheric 3urface Layer (ASL). Sample data are presented and discussed. Comparison with the full-scale results from TTU are presented and show generally good agreement; however, the largest peak suctions are often underestimated by the model data measured at edge and corner roof locations. Some ideas are presented here to possibly explain these model-scale, full-scale anomalies.

Physical modelling of the atmospheric surface layer

Abstract Wind effects on low-rise buildings and dispersion of pollutants from low-level sources result from wind in the lowest region of the atmospheric boundary layer (ABL) - the atmospheric surface layer (ASL) which has a thickness of approximately 100 m. Turbulent shear stress in thermally neutral and unstable flows decreases by only 5 to 10% of the surface shear stress across the ASL. The results of research to physically model deep layers of flow in a boundary-layer wind tunnel having this property are presented herein. Boundary-layer flows have been developed that model properties of the ASL over a layer 0.5 m in thickness. Flow properties of the modelled ASL are compared to micrometeorological measurements taken on a 48.8-m high tower at the Texas Tech University (TTU) field site.

Wind-tunnel modelling of the atmospheric surface layer

Modelling of low-rise structures in the boundary-layer wind tunnel requires that the investigator focus on the lowest 100 m of the atmospheric boundary layer; the atmospheric surface layer (ASL). Most of the key flow properties in this lowest portion of the atmospheric boundary layer (ABL) have been successfully modelled in the wind tunnel for some time. However, this work demonstrates that two additional open-terrain flow properties may also be modelled with the wind tunnel: (i) the vertical distribution of Reynolds shear stress and; (ii) the lateral fluctuations of wind velocity and their power spectra.

Selected International Receptor-Based Air Quality Standards

Abstract The ambient air quality standards (AAQS) of twenty-one nations for eight commonly regulated substances are presented. Many countries are adding a receptor-based component to their air quality management, which traditionally have been emission oriented. Automation of air quality monitoring stations has meant that local air quality evaluation can now be more easily achieved. However, a majority of countries have no active air quality standards (emission or receptor-based) or ambient air quality monitoring. One possible monitoring procedure is outlined and the variation in international standards is discussed.

Reduction of Roof Wind Loads by Architectural Features

The devastating impact of Hurricane Andrew on the low-rise buildings of southern Florida and coastal Louisiana [Refs. 1 and 2] illustrated that destructive winds may produce very high pressures at some specific locations on a domestic home or light industrial/commercial structure. This study shows that the use of vertical porous screens across the roof comers on this style of building will dramatically reduce the local and area-averaged uplift loads that have to be resisted by the roof. Full-scale and wind-tunnel modelling research is discussed which shows that the regions of extreme uplift on a roof are due to the corner vortices lying on the roof surface. The wind tunnel was then used to investigate the impact of various rigid gauze screens on the formation of these vortices. Ten screen shapes were investigated, each of which reduces the wind uplift loads to varying degrees and may also be an architecturally acceptable addition to the design of a low-rise building.

Lessons from Hurricane Andrew

At dawn on 26 August 1992 Hurricane Andrew made its first landfall on the Louisiana coast at Point Aufer Island. This category four storm had already caused 16,000 M of insured losses [Ref.1] in southern Florida before it hit a rural region of southern Louisiana near Morgan City, 115 km west of New Orleans. The winds caused by Hurricane Andrew effected the built environment of coastal Louisiana in various ways that depended on the level of designer input and the construction quality control. A variety of commercial buildings, dwellings and engineered structures were examined by a United States National Science Foundation funded disaster team and a summary of their findings is presented here; along with some useful design suggestions for hurricane or cyclone-prone areas.

Roof Surface Wind Speed Distributions on Low-rise Buildings

On low-rise buildings the damage to and destructive removal of small roofing elements forming a porous roof membrane, such as tiles, shingles and shakes, is largely controlled by the heal mean andpeak wind speeds that exist just above the roof surface. Some typical high speed regions have been identified by the selective removal of cladding elements during high wind events [Refs. 1 and 2]. Frequently these high speed regions close to the roof surface are comer or ridge vortices. This study endeavours to map the mean surface wind speeds in the wind tunnel on some typical house geometries at a scale of 1:25 with a robust hot-probe anemometer. In one configuration these data were confirmed by full-scale measurements. Some peak wind-speed data were also collected at selected locations with a highly responsive hot-film anemometer. Both sloped and near-horizontal roofs have been investigated. In all geometries, a locally increased mean wind speed of up to sixty percent above the approach flow value was found fo...

Low-Rise Architectural Aerodynamics: The Texas Tech University Experimental Building

The United States National Science Foundation sponsored Colorado State University/Texas Tech University Cooperative Programme on Wind Engineering (CPWE) provides a focus for research on wind effects on man-made, low-rise buildings and structures. This unique cooperative programme permits a creative binding of experience in post-disaster evaluation, architectural aerodynamics, building codes, wind-tunnel simulation and computational fluid dynamics modeling methods. This paper summarizes some results extracted from one part of a total of eight components to the project. The CSUITTU CPWE is a five year programme of model and full-scale experimentation which is currently in its third year.

Physical modelling of roof-top helicopter exhaust flow dispersion

Abstract A technique for physically modelling the interaction of helicopter rotor flows with the natural wind in a boundary-layer wind tunnel is described. This technique is used to measure the dilution of helicopter exhaust fumes at the roof-level air intakes near the heliports on top of the new American Stores Company Headquarters building in Salt Lake City, Utah. The dilution values may then be compared to odor and health threshold limits in the literature. Physical modelling of the interaction of the helicopter rotor downwash and the ambient wind around a complex architectural roof shape was used to determine the suitability of the locations chosen for the building air intakes. This approach is appropriate where any heliport operation interacts with the HVAC system of an office building or hospital.