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This work investigated the influence of crosswinds and leg positions on the aerodynamics of an articulated cycling mannequin on a track bicycle. Force, wake total pressure and wake velocity measurements were made in a low-speed sports wind tunnel of closed-circuit type. The freestream velocity and wheel speeds were kept at 15 m/s . The crank angle of the mannequin was varied across a pedal cycle. Yaw angles from 0 ∘ to 20 ∘ were examined. The experimental results reveal that the leg position significantly affects the aerodynamic performance of a cyclist. At high yaw angles, the aerodynamic drag on the cyclist showed noticeable deviations between most leg positions and their 180 ∘ -apart pairs. A wake analysis technique effectively captured the influence of leg positions on drag. The total pressure deficit contributes dominantly to the overall drag. The wake pressure contours demonstrate how leg-wheel interaction affects the total pressure distribution and drag under crosswinds. This study offers valuable insights into the flow behavior and drag generation around a cyclist with varying leg positions under crosswinds. [ABSTRACT FROM AUTHOR]

The wheels of a passenger vehicle contribute to a significant part of the vehicle's aerodynamic drag. The previous research has shown that the flow is sensitive to small geometrical variations of the tyre, such as its shoulder profile and tread pattern. This work investigates the effect of altering the tyre profile in the transition region between the tyre and the rim by adding a so-called rim protector. Full-scale wind tunnel tests capturing forces, flow fields and surface pressures were conducted for three tyre variants in combination with two rim configurations on a crossover SUV. With a low rim protector, the forces and flow fields were similar to the reference tyre without a rim protector for both rims. With a wide, protruding, rim protector on the open rim, a larger and more outwashed front wheel wake was obtained with differences in the vortex structures, resulting in a drag penalty of 0.017 C D . The altered front wheel wake reduced the shielding of the rear wheel, resulting in differences in the rear wheel wake and base pressure. With a closed rim, the differences with the wide rim protector were much smaller with only a slight drag increase compared to the reference, demonstrating that there can be a strong interaction between the tyre and rim design. [ABSTRACT FROM AUTHOR]

Reactive air brazing of 3YSZ ceramic and aluminized Crofer22H stainless steel was conducted using Pd-modified Ag-2CuO fillers in this study. The influence of Pd content on the interfacial microstructure and the mechanical properties of the joints at room (25 °C) and high temperatures (600 °C) was thoroughly investigated. The results revealed that an increase in Pd content resulted in a decrease in the solubility of O element in the filler system, thereby altering the form of CuO at high temperatures and significantly enhancing its reactivity with aluminized Crofer22H stainless steel. Additionally, there was a significant deterioration observed in the wettability of the fillers on ceramics. Well-joined joints were only achieved with the use of Ag2CuO-3 wt.% Pd filler, resulting in a 27.9% increase in room temperature shear strength due to enhanced interface reaction. At 600 °C, plastic deformation caused Ag-based filler to soften through dynamic recrystallization, but the addition of Pd dissolved in the matrix produced a solute drag effect that inhibited this process and increased joint shear strength by 41.1%. [ABSTRACT FROM AUTHOR]

A vortex beam of light is used to enhance and control the lateral and rotary light drag effects in three-level graphene quantum dots. In this study, by using a vortex beam, two practical parameters are introduced to control the optical properties of the system and consequently enhance both the lateral and rotary light drag effects. These parameters are the orbital angular momentum and the azimuthal phase of the applied controlling vortex beam. By increasing the orbital angular momentum of the vortex beam, the absorption of the probe field decreases, while the lateral and rotary light drag effects increase. Furthermore, we found that the azimuthal phase of the vortex beam has a substantial impact on the optical properties of the probe field. Thus, it can be utilized as an efficient parameter for enhancing and controlling light drag effects. [ABSTRACT FROM AUTHOR]

Orographic gravity waves (OGWs) are an important mechanism for coupling of the free atmosphere with the surface, mediating the momentum and energy transport and influencing the dynamics and circulation especially in the middle-atmosphere. Current global climate models are not able to resolve a large part of the OGW spectrum and hence, OGW effects have to be parameterized in the models. Typically, the only parameterized effect is the OGW induced drag. Despite producing the same quantity as an output and relying on similar assumptions (e.g. instantaneous vertical propagation), the individual OGW parameterization schemes differ in many aspects such as handling of the orography, the inclusion of non-linear effects near the surface and the tuning of the emergent free parameters. In this study, we have reviewed 7 different parameterizations, which are used in 9 different CMIP6 models. We report pronounced differences in the vertical distribution and magnitude of the parameterized OGW drag between the models and study to what extent the inter-model differences can be traced back to the difference in the type and tuning of the schemes. Finally, we demonstrate how the OGW drag differences project to the intermodel differences in the stratospheric dynamics. The study can pave the way for a more systematic research of the OGW parameterizations in the future, with an ultimate goal of lowering the amount of uncertainty of the future climate projections connected with the parameterized effects of unresolved orography. [ABSTRACT FROM AUTHOR]

The Coulomb drag is a many-body effect observed in proximized low-dimensional systems. It appears as emergence of voltage in one of them upon passage of bias current in another. The magnitude of drag voltage can be strongly affected by exchange of plasmonic excitations between the layers; however, the reverse effect of Coulomb drag on properties of plasmons has not been studied. Here, we study the plasmon spectra and damping in parallel two-dimensional systems in the presence of Coulomb drag. We find that Coulomb drag leads to selective damping of one of the two fundamental plasma modes of a coupled bilayer. For identical electron doping of both layers, the drag suppresses the acoustic plasma mode; while for symmetric electron-hole doping of the coupled pair, the drag suppresses the optical plasma mode. The selective damping can be observed both for propagating modes in extended bilayers and for localized plasmons in bilayers confined by source and drain contacts. The discussed effect may provide access to the strength of Coulomb interaction in 2d electron systems from various optical and microwave scattering experiments. [ABSTRACT FROM AUTHOR]

Cycling time trials are characterised by riders adopting positions to lessen the impact of aerodynamic drag. Aerodynamic positions likely impact the power a rider is able to produce due to changes in oxygen consumption, blood flow, muscle activation and economy. Therefore, the gain from optimising aerodynamics must outweigh the potential physiological cost. The aim was to establish the relationship between energy expenditure and aerodynamic drag, with a secondary aim to determine the reliability of a commercially available handlebar mounted aero device for measuring aerodynamic drag. Nine trained male cyclists volunteered for the study. They completed 4 × 3200 m on an outdoor velodrome where stack height was adjusted in 1 cm integers. The drag coefficient (CdA), oxygen consumption and aerodynamic-physiological economy (APE) were determined at each stack height, with data used to model 40 km TT performance. Small to moderate effect sizes (ES) in response to stack height change were found for CdA, APE and energy cost. The change in TT time was correlated to ∆aerodynamic drag and ∆APE. Meaningful impacts of change in stack height on CdA, APE, energy cost and predicted TT performance, are apparent with highly individualised responses to positional changes. [ABSTRACT FROM AUTHOR]