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Mara T.G.,University of Western Ontario | Galsworthy J.K.,University of Western Ontario | Galsworthy J.K.,Current Address Rowan Williams Davies and Irwin Inc. | Savory E.,University of Western Ontario
Wind and Structures, An International Journal | Year: 2010

The focus of this article is on the assessment of vertical wind vector components and their aerodynamic impact on lattice framework, specifically two distinct sections of a guyed transmission tower. Thunderstorm winds, notably very localized events such as convective downdrafts (including downbursts) and tornadoes, result in a different load on a tower's structural system in terms of magnitude and spatial distribution when compared to horizontal synoptic winds. Findings of previous model-scale experiments are outlined and their results considered for the development of a testing rig that allows for rotation about multiple body axes through a series of wind tunnel tests. Experimental results for the wind loads on two unique experimental models are presented and the difference in behaviour discussed. For a model cross arm with a solidity ratio of approximately 30%, the drag load was increased by 14% when at a pitch angle of 20°. Although the effects of rotation about the vertical body axis, or the traditional 'angle of attack', are recognized by design codes as being significant, provisions for vertical winds are absent from each set of wind loading specifications examined. The inclusion of a factor to relate winds with a vertical component to the horizontal speed is evaluated as a vertical wind factor applicable to load calculations. Member complexity and asymmetric geometry often complicate the use of lattice wind loading provisions, which is a challenge that extends to future studies and codification. Nevertheless, the present work is intended to establish a basis for such studies. Source


Adaramola T.F.,University of Ibadan | Adaramola T.F.,International Institute Of Tropical Agriculture | Adaramola T.F.,Forestry Research Institute of Nigeria | Sonibare M.A.,University of Ibadan | And 5 more authors.
Plant Genetic Resources: Characterisation and Utilisation | Year: 2014

The literature in recent times lacks adequate report on the utilization and genetic improvement programmes on Dioscorea dumetorum. Despite the wide application of this yam species in agriculture and medicine, it suffers neglect while other species are becoming increasingly popular. Therefore, it is pertinent to focus on research that will bring this species to the limelight. The aim of the present study was to evaluate the ploidy levels, morphological traits and secondary metabolite profile of 53 accessions of D. dumetorum from six countries in West and Central Africa. Ploidy levels were determined using flow cytometry. Overall, 18 morphological traits were recorded from the above- and underground parts of the plant. The 53 accessions were subjected to statistical analyses using the data on ploidy levels, morphological traits and qualitative phytochemical screening. A total of 15 accessions from the generated clusters were selected for thin layer chromatographic and quantitative phytochemical analyses. The analyses revealed diploid (2x) and triploid (3x) levels in these accessions. The pruned dendrogram derived from agglomerative hierarchical clustering based on the distance matrix revealed three main groups, showing a relationship between sex and ploidy level in the accessions and exhibiting sufficient cluster variability that may be important in designing breeding programmes. The crop was also shown to possess metabolites such as alkaloids, saponins and flavonoids, which are known to be useful in the application of phytomedicine. Genetic variability observed among the yam accessions in this study can be used for breeding purposes and to broaden the genetic basis of the crop for efficient utilization of the genetic potential possessed by this species. Copyright © NIAB 2014 Source


Jackson D.W.T.,Current Address Rowan Williams Davies and Irwin Inc. | Beyers J.H.M.,Current Address Rowan Williams Davies and Irwin Inc. | Lynch K.,National University of Ireland | Cooper J.A.G.,Current Address Rowan Williams Davies and Irwin Inc. | And 2 more authors.
Earth Surface Processes and Landforms | Year: 2011

The behaviour of offshore-directed winds over coastal dune and beach morphology was examined using a combination of modelling (3-D computational fluid dynamics (CFD)) and field measurement. Both model simulations and field measurements showed reversal of offshore flows at the back beach and creation of an onshore sediment transport potential. The influence of flow reversals on the beach-dune transport system and foredune growth patterns has previously received little attention. Detailed wind flow measurements were made using an extensive array of mast-mounted, 3-D ultrasonic anemometers (50Hz), arranged parallel to the dominant incident wind direction. Large eddy simulation (LES) of the offshore wind flow over the dune was conducted using the open-source CFD tool openFOAM. The computational domain included a terrain model obtained by airborne LiDAR and detailed ground DGPS measurements. The computational grid (~22 million cells) included localized mesh refinement near the complex foredune terrain to capture finer details of the dune morphology that might affect wind flows on the adjacent beach. Measured and simulated wind flow are presented and discussed. The CFD simulations offer new insights into the flow mechanics associated with offshore winds and how the terrain steering of wind flow impacts on the geomorphological behaviour of the dune system. Simulation of 3-D wind flows over complex terrain such as dune systems, presents a valuable new tool for geomorphological research, as it enables new insights into the relationship between the wind field and the underlying topography. The results show that offshore and obliquely offshore winds result in flow reversal and onshore directed winds at distances of up to 20m from the embryo dune toe. The potential geomorphological significance of the findings are discussed and simple calculations show that incoming offshore and obliquely offshore winds with mean velocities over 13m s-1 and 7m s-1, respectively, have the potential to create onshore-directed winds at the back beach with mean velocities above 3.3m s-1. These are above the threshold of movement for dry sand and support previous conclusions about the significance of offshore winds in dune and beach budget calculations. © 2011 John Wiley & Sons, Ltd. Source


Brooks A.,Current Address Rowan Williams Davies and Irwin Inc. | Dale J.,Current Address Rowan Williams Davies and Irwin Inc. | Gamble S.,Current Address Rowan Williams Davies and Irwin Inc. | Kriksic F.,Current Address Rowan Williams Davies and Irwin Inc.
Proceedings of the International Conference on Cold Regions Engineering | Year: 2015

Methods for evaluating snow loads on roofs are described within building standards and codes such as American Society of Civil Engineers 7 and the National Building Code of Canada. These recommendations are often simplified and generic in order to be applicable to most structures and, as a result, do not account for the unique aerodynamics that can occur around a structure. In addition, these codes and standards do not address serviceability concerns, such as accessibility to building entrances, nor identify where mechanical air intakes may be prone to snow ingestion as is common to buildings located in cold regions. Scale model testing within an open channel water flume allows for the rapid assessment of the building aerodynamics and snow drifting conditions for the purposes of design. This paper presents snow accumulation patterns representing a snowfall event from a single direction for a building with commonly seen geometries including roof steps, arched roofs, and a projecting tower with mechanical penthouse. Multiple test directions are presented to illustrate the influence of wind directionality and resulting building aerodynamics on snow accumulations at grade level, on roof areas, and where mechanical intake equipment is often sited.Parapets, canopies, and recommendations for mechanical air intakes for reducing problematic snow accumulations are presented and discussed. © ASCE. Source

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