Outline of the Variscan basement of Sardinia

In Sardinia a quasi-complete section of the southern branch of the Variscan orogenic belt crops out, characterized by non-metamorphosed to high-grade rocks, whose age ranges from Early Cambrian to Early Carboniferous, and that are involved in a complex polyphase deformation. The main result of the Variscan orogeny in Sardinia is a tectono-metamorphic partition with, from north to south: an Inner Zone, with medium to high grade metamorphism, thrusted over a Nappe Zone, with green schist metamorphism that overthrusted a Foreland Zone affected by very low grade regional metamorphism. The pre-Variscan succession is well exposed in the Foreland and Nappe zones where four main synthemes can be recognized: i) a Lower Cambrian to Lower Ordovician terrigenous and carbonatic succession deposited in the Gondwana passive margin, sealed by an angular unconformity related to the Sardic Phase, ii) a Middle-Upper Ordovician magmatic complex, both intrusive and effusive, probably related to an Andean-type plate convergence, iii) a terrigenous to carbonatic succession from Late Ordovician to Early Carboniferous, again related to a passive margin evolution; iv) finally a flyschoid Culm-like succession accredited to Early Carboniferous

Virtual skeleton methodology for athlete posture modification in CFD simulations

This study focuses on the aerodynamic influence of athlete posture in sports aerodynamics. To analyze a specific posture, wind tunnel measurements and computer simulations are commonly employed. For computer simulations, the growing trend is to use 3D scanning to create accurate representations of an athlete’s geometry. However, this process becomes cumbersome and time-consuming when multiple positions need to be scanned. This work presents a methodology to use a virtual skeleton to perform modifications of an athlete’s posture. This is an efficient approach that can be applied directly to a scanned geometry model, and that allows easy modification and use in optimization procedures. The methodology is applied to two different cases; small adjustment of arm position for a time-trial cyclist, and large alteration of a standing alpine skier into a tucked position. Computational fluid dynamics simulations show that similar results are obtained for aerodynamic drag using the proposed methodology as with geometry models obtained from 3D scanning. Less than 1% difference in drag area was found for the cyclist, and less than 2% difference for the skier. These findings show the method’s potential for efficient use in sports aerodynamics studies.publishedVersio

Configurable convolutional neural networks for real-time pedestrian-level wind prediction in urban environments

Urbanization has underscored the importance of understanding the pedestrian wind environment in urban and architectural design contexts. Pedestrian Wind Comfort (PWC) focuses on the effects of wind on the safety and comfort of pedestrians and cyclists, given the influence of urban structures on the local microclimate. Traditional Computational Fluid Dynamics (CFD) methods used for PWC analysis have limitations in computation, cost, and time. Deep-learning models have the potential to significantly speed up this process. The prevailing state-of-the-art methodologies largely rely on GAN-based models, such as pix2pix, which have exhibited training instability issues. In contrast, our work introduces a convolutional neural network (CNN) approach based on the U-Net architecture, offering a more stable and streamlined solution. The process of generating a wind flow prediction at pedestrian level is reformulated from a 3D CFD simulation into a 2D image-to-image translation task, using the projected building heights as input. Testing on standard consumer hardware shows that our model can efficiently predict wind velocities in urban settings in real time. Further tests on different configurations of the model, combined with a Pareto front analysis, helped identify the trade-off between accuracy and computational efficiency. This CNN-based approach provides a fast and efficient method for PWC analysis, potentially aiding in more efficient urban design processes

Aerodynamic Investigation of Tucked Positions in Alpine Skiing

The purpose of this investigation was to examine the aerodynamics of tucked positions in competitive alpine skiing. To further our understanding of how a skier’s position affects the air flow and the resulting aerodynamic drag, a combination of both experimental and simulation methods was used. This study focused in particular on the effect of skier torso and thigh angles relative to the air flow direction, as these two angles have been previously found to be important determinants of aerodynamic performance in tucked positions. Two top 30 world-ranked skiers were investigated in two different wind tunnels, and the results were compared with Computational Fluid Dynamics (CFD) simulations performed using a 3D scan of one of the athlete. To quantify the effect of torso and thigh angles on skier drag, changes in drag were measured relative to baseline positions. Skier drag area increased by approximately 0.8 and 1.2% per degree increase in torso and thigh angles relative to the baseline position, respectively. This trend was consistent between both of the experimental wind tunnel tests as well as the CFD simulations, indicating good agreement between methods. The CFD simulations further indicated that the air flow about the lower legs made the largest contribution to skier drag, accounting for as much as 40–50% of the total drag area in low tuck positions. Based on these findings, a low tuck position where the torso angle approaches 0° and the knees help to fill the gap behind the armpits will minimize skier aerodynamic drag.publishedVersio

Application of a PI-controller to a 25 MW Floating Wind Turbine

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Preliminary Sizing and Optimization of Semisubmersible Substructures for Future Generation Offshore Wind Turbines

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Influence of Fabric Structural Attributes on Their Aerodynamic Behavior

ABSTRACT The aerodynamic properties of 15 knitted fabrics of varying cover factor, yarn, and fiber compositions were investigated for their aerodynamic properties on circular cylinders in a wind tunnel. Measurements of the drag force, pressure distribution, and the Particle Image Velocimetry (PIV) technique were used in order to obtain a better understanding of the effects of yarn, fiber composition, cover factor, and elastic deformation on the flow field and drag coefficient. It was clearly demonstrated from the drag force measurements that the yarn construction and fiber composition have a substantial effect on the drag coefficient (C D ), with fabrics composed of spun yarn experiencing no C D -drop as opposed to those composed of filament yarn, and being almost unaffected by the cover factor in the range of Reynolds numbers investigated. Hairiness of the spun yarn was found to minimise the drag-reducing effect of the boundary layer transition and increase the trans-critical drag. The hairy surface layer also appeared to retard the turbulent boundary layer as almost no pressure recovery was observed prior to separation on the cylinder model. The effect of elastic deformation was investigated by image analysis of scanned textile samples, and demonstrated that surface roughness might not be directly correlated to cover factor when the fabrics are stretched. Different elastic behavior of fabrics with different cover factors was also found to affect the structure of the knit surface and thus their aerodynamic behavior. The onset of drag crisis found in drag measurements confirmed the deviation from a sequence determined solely by cover factor

The Dimensioning Sea Loads (DIMSELO) project:Paper

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In vitro phenotypic characterisation of two genotype I African swine fever viruses with genomic deletion isolated from Sardinian wild boars

African swine fever virus (ASFV) causes a devastating disease affecting domestic and wild pigs. ASF was first introduced in Sardinia in 1978 and until 2019 only genotype I isolates were identified. A remarkable genetic stability of Sardinian ASFV isolates was described, nevertheless in 2019 two wild boar isolates with a sustained genomic deletion (4342 base pairs) were identified (7303WB/19, 7212WB/19). In this study, we therefore performed in vitro experiments with monocyte-derived macrophages (moMФ) to unravel the phenotypic characteristics of these deleted viruses. Both 7303WB/19 and 7212WB/19 presented a lower growth kinetic in moMФ compared to virulent Sardinian 26544/OG10, using either a high (1) or a low (0.01) multiplicity of infection (MOI). In addition, flow cytometric analysis showed that both 7303WB/19 and 7212WB/19 presented lower intracellular levels of both early and late ASFV proteins. We subsequently investigated whether deleted virus variants were previously circulating in wild boars in Sardinia. In the four years preceding the last genotype I isolation (February 2015–January 2019), other eight wild boar isolates were collected, all belonging to p72 genotype I, B602L subgroup X, but none of them presented a sustained genomic deletion. Overall, we observed the deleted virus isolates in Sardinia only in 2019, at the end of a strong eradication campaign, and our data suggest that it might possess an attenuated phenotype in vivo. A better understanding of ASFV evolution in endemic territories might contribute to development of effective control measures against ASF