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Aerodynamic design of wind barriers on bridges: Wind tunnel experiments

Studies on the atmospheric boundary layer (ABL) are important for the improvement of human health and safety. Their results increase the understanding of air pollutant dispersion and wind loads on structures and vehicles. Most ABL studies are conducted in a wind tunnel where it is generally necessary to compromise between two contradictory demands: on the one hand, the ABL wind tunnel model should be as large as possible to increase details of the simulated flow, and on the other hand, a structural wind tunnel model that is too large can cause blockage effects in the wind tunnel test section. These scaling issues were comprehensively studied at the Munich Institute of Technology where commonly used ‘ Counihan’ vortex generators were redesigned for purposes of part-depth ABL simulations. In this seminar, a short overview of the Counihan method for the ABL wind tunnel modeling will be given and results of several part-depth ABL simulations using redesigned vortex generators will be presented. Recently, wind tunnel tests were carried out at the University of Florence to determine an optimal aerodynamic design of wind barriers for two Croatian bridges. The wind-induced instability of road vehicles on these bridges is a great problem and they have had to be closed to traffic often due to safety requirements. In the second part of the presentation, some effects of wind barrier design on a flow field will be presented. A significant reduction in mean velocities was observed after placing a barrier on bridges. An increase of the barrier height and a reduction of the barrier porosity result in a decrease of velocities in the protected region of the bridge. This study was extended at the University of Notre Dame where experiments have been carried out to determine the transient aerodynamic loads on vehicles.

Natural wind simulation; aerodynamic design of wind barriers on bridges; transient aerodynamic loads on vehicles; wind tunnel experiments

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