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Wind turbines are exposed to the turbulent wind of the atmospheric boundary layer. Consequently, the aerodynamic forces acting on the rotor blades are highly complex. To improve the understanding, a common practice is the experimental or numerical investigation of 2d (wind turbine) blade sections. In these investigations, the flow around the 2d blade section is assumed to be two‐dimensional; however, 3d effects are known to occur. Therefore, we combine 2d CFD simulations and experimental investigations in a wind tunnel with a 2d wind turbine rotor blade section at full‐scale (i.e., chord length c=1.25m and chord‐based Reynolds number of Rec=4.7·106). In the wind tunnel, the inflow turbulence intensity is TI≈1.5%. To avoid wall effects biasing the results, the profile does not span the whole test section. The profile was equipped with two rows of pressure taps around the airfoil, close to the center, to monitor the time‐resolved aerodynamic response as well as the flow around the airfoil. The normal force, cp curves, and the separation point are analyzed. While 2d simulations and experiments match well, in the experiments, we find natural instabilities, that is, local and temporal variations of the flow separation point at angles of attack close to the maximum lift that are not triggered externally, for example, by inflow variations. [ABSTRACT FROM AUTHOR]

Ice and snow shedding events on cable-supported bridges around the world have become more frequent in recent years. Although they pose a risk to bridge users and lead to lengthy bridge closures, the research so far has focused mainly on the development of various countermeasures and the aerodynamic behaviour of cables with ice or snow accretions. In this paper, a wind tunnel investigation aimed at simulating atmospheric conditions to reproduce natural accretion and shedding of ice and snow from different bridge cable surfaces is presented. The experimental investigation was carried out at two different climatic wind tunnel facilities and involved the use of two different solar simulators to simulate the effect of solar radiation on the melting and shedding process. It was found that both the colour of the cable surface and the surface modifications had a significant influence on the melting and shedding of ice and snow. Whilst the cable colour affected the heating rate of the cable surface and governed the shedding rate of smooth cable sections, the use of surface modifications such as steel wire mesh was more effective in retaining the accretions for longer and breaking them into smaller pieces. The analysis further revealed how the non-uniform heat transfer distribution around the cables affects the surface temperatures at specific locations and how much solar irradiance is approximately transmitted through the accretions onto the cable surface. These findings improve the fundamental understanding of ice shedding from bridge cables and demonstrate the performance benefits of cable surface modifications in terms of risk mitigation for bridge users. • Ice shedding was studied in two different wind tunnels with solar simulators. • Ice and snow melting rate increased on darker bridge cable sheaths. • Surface modifications impact ice shedding performance more than sheath colour. • Wire mesh on bridge cables can reduce ice shedding risk significantly. [ABSTRACT FROM AUTHOR]

Atmospheric Boundary layer wind tunnels (ABLWT) dedicated to building safety and comfort have been operated by CSTB in Nantes since 1971. Because ABLWT only deal with reduced scale models of real structures, the necessity of a larger wind tunnel, the Jules Verne Climatic wind tunnel (CWT), able to reproduce extreme wind loads on real scale structures arose in the years 80. Hence, it became a major European facility operating for improvement of the safety, quality and environmental impact of buildings and civil engineering works as well as products from industrial fields (transportation, energy...) with respect to strong winds and other climatic hazards. Both wind tunnel types, the ABLWT and the CWT are complementary and used for studying the effect of wind on the same structures at two different scales, when the effect of wind scaling is important. During the 2018 year, several modifications were made to the CWT facility. The atmospheric test section of the existing facility was elongated preserving the initial advantages, very large test section (approximately 120 m²) with wind velocity performance compatible with many applications (up to 90 km/h). This new test section makes it possible to simulate turbulent wind and driving rain testing. The sand winds capabilities have been maintained in the new design, despite the closed loop configuration, by fitting a filtering. The modifications of the wind tunnel geometry now offer a long test section upstream the turning vanes where a whole set of new tests can be carried out, as windmill field, natural ventilation of urban environments, slender structures (large bridges, pylons, cable transport systems,) [ABSTRACT FROM AUTHOR]

Abstract: Ventilated roof is a common practice of building design in the Scandinavian countries. One problem with this design is the penetration of blowing snow into the ventilated space in the roof. The rate of snow penetration is largely dependent on the design of the eave. In Norway and Greenland, different design solutions have been tried, based on experience and intuition. However, these solutions have, until now, never been verified under controlled laboratory conditions. The ability to prevent snow penetration and still allow ventilation of the ventilated roof or attic is tested for several different eave constructions. The testing has been performed in a wind tunnel in an environment of cold air and with production of artificial snow. The scale of the eave constructions was 1:1. Most of the designs in the experiment are common in Scandinavian building practice. However, new innovative solutions designed for extreme snow drifting environments in Greenland were also tried. Also, the effect of a deflector to deflect snow particles away from the ventilation openings was tested. Over 400 times more snow accumulated in the construction allowing the most snow to enter the roof compared to the construction designed for extreme environments. [Copyright &y& Elsevier]