Current environmental concerns are increasingly forcing manufacturers to reduce the use of petroleum derivatives in order to reduce their carbon footprint. The use of new plant-based materials is ...therefore an interesting alternative to plastics. A certain number of plant fibers have been rediscovered for use in the form of agro-composites; Nettle fiber is one of them. The objective of this review is thus to take stock of current knowledge on the European Nettle fiber (Urtica Dioica) and its asian version (Boehmeria nivea, or Ramie), which are too often confused. This "weed," which has been used since antiquity, is coming back into fashion thanks to the highlighting of some of its properties but also to its simplicity of cultivation. The association PLA/Nettle, lending itself perfectly to this concept of modern ecological material 100% biodegradable, is also highlighted in this work where the intrinsic qualities of each component are detailed based on the promising uses of this agro-composite mentioned in the literature or the automotive industry.
Recently, significant advances have marked the scientific knowledge of the formation flight of migratory birds. Both experimental and theoretical research have played a central role in understanding ...the aerodynamic mechanisms associated with this behavior, laying the groundwork for future investigations into the benefits of group formation. These studies have specifically demonstrated the energy savings achieved by birds adopting this practice. Technological evolution, in turn, has opened new perspectives, allowing an in-depth experimental understanding of the flight behaviors of birds in formation, ranging from their energy saving to sophisticated aerodynamic strategies. Studies converge towards an increasing recognition of the complexity and variability of the mechanisms governing formation flight in different avian species. Recent progress in computer modeling has generated impressive visual representations of V-formation flight, prompting several hypotheses about its functions and mechanisms. However, the challenge persists in the ability to test these hypotheses. In conclusion, a multidisciplinary approach involving biologists, engineers, mathematicians, computer scientists, and physicists is essential to unravel the mysteries of the aerodynamics of V-formation flight in migratory birds. This literature review aims to compile studies addressing aerodynamic questions related to the formation flight of migratory birds, exploring various aspects from aerodynamic modeling to energy saving and formation optimization.
Many recent studies show that the performance of Savonius turbines can be considerably increased by using wind deflectors. Axisymmetric deflectors are particularly interesting; they concentrate the ...wind flow in all directions. This study aims to aerodynamically optimize the truncated cone deflector shape through transient 3D CFD simulations using sliding mesh techniques. To reduce the mesh size and thus the simulation time, symmetrical boundary conditions were applied to rotating body faces. A mesh grid sensitivity study was conducted to define the optimum mesh size. Additionally, hybrid numerical approaches combining coupled and SIMPLE solvers were particularly influential in reducing computational time. Concave- and convex-arced-shaped faces deflectors were compared to the original truncated cone deflector, showing an increase in the performance for the convex type and a decrease for the concave one. Then, eight cases involving convex spline shape deflectors were simulated. All these deflectors had an equal volume to the original truncated cone deflector. One of the cases showed a 20% average increase in the performance over the original deflector. This result shows the importance of the geometrical shapes in the design of axisymmetric deflectors.
While the recent literature on Whole-Body Cryotherapy pointed to its beneficial systemic effects on inflammatory markers in rheumatoid arthritis, it was not clear whether it could also have more ...localized effects, with the attainment of analgesic thresholds on hands that are usually protected during protocols. Twenty-five young, healthy subjects (12 males aged 25.1 ± 3.5 years and 13 females aged 23.5 ± 2.6 years) agreed to participate in this study. Two study groups were defined: (1) a control group with a hand fully gloved and (2) an experimental group with a partially ungloved hand during the WBC session. In both groups, the achievement of analgesic thresholds of skin temperature was established through thermal imaging, focused on the measurement of temperatures at the different joint locations. Using a new protocol with direct exposure of the hands during the last 40 s of a standard WBC session of 3 min at −110 °C made it possible to respect this risk/benefit balance. Infrared thermography analyses revealed that for all regions of interest (except MCP and IP, CMP for thumb), there was a clinically meaningful reduction of skin temperature in participants from the experimental group. The thermal analysis suggests that a protocol of Whole-Body Cryotherapy at −110 °C where hands must be ungloved during 40 s could be a useful tool for the management of hand rheumatoid arthritis by achieving local antalgic thresholds.
This study aims to optimize the thermodynamic performance of a cold storage distribution box through the integration of a ventilation system. To achieve this goal, a prototype constructed from ...expanded polystyrene is developed, incorporating an active ventilation system to ensure cold temperature uniformity. Thermocouples are integrated into the device to monitor the temporal temperature evolution with and without ventilation. Concurrently, a 2D thermo-aerodynamic investigation is conducted using computational fluid dynamics (CFD). The numerical modeling of the thermodynamic behavior of the cold source employs polynomial laws as input data for the computational code (UDF functions). A comparison between experimental and numerical results reveals the computational code’s accurate prediction of the temporal temperature evolution in the cold storage distribution box, particularly under forced convection conditions. The findings indicate that in the absence of ventilation, thermal exchanges primarily occur through air conduction, whereas with ventilation, exchanges are facilitated by convection. Overall, forced convection induced by the inclusion of a ventilation device enhances thermal transfers and the thermodynamic performance of the cold storage distribution box. Furthermore, air mixing limits thermal stratification, thereby facilitating temperature homogenization.
The gradual development of government policies for ecological transition in the modern construction sector leads researchers to explore new alternative and low environmental impact materials with a ...particular focus on bio-sourced materials. In this perspective, the mechanical, thermal insulation, and the sound absorption performances of a spent coffee grounds/potato starch bio-based composite were analyzed for potential application in buildings. Based on thermal conductivity and diffusivity tests, the coffee grounds waste biocomposite was characterized as an insulating material comparable with conventional thermal insulation materials of plant origin. Acoustical tests revealed absorption coefficients in the same range as other conventional materials used in building acoustical comfort. This bio-sourced material presented a sufficient compressive mechanical behavior for non-load-bearing structures and a sufficient mechanical capacity to be shaped into building bricks. Mechanical, thermal, and acoustic performances depend on the moisture environment. The groundwork was laid for an initial reflection on how this composite would behave in two opposite climates: the continental climate of Reims in France and the tropical climate of Belém in Brazil.
Raw earth bricks made from the soil of the Chalky Champagne region (France) have been used for at least two millennia in construction, a promising heritage in the context of reducing the carbon ...emissions of buildings. The present experimental study aims to measure the physical, mechanical, thermal, and hydric properties of adobes collected from a local village barn. The results show a high chalk content, estimated at 71%, and a clay content, acting as a binder, of 14%. Despite limited load-bearing capacity, these lightweight adobes are suitable for current single-story constructions, while their hydrothermal properties classify them as excellent moisture regulators for occupants. In association with other bio-sourced materials such as starch-beet pulp bricks, Chalky Champagne adobes yield promising insulating properties, and meet the criteria defined by current energy standards.
One possible approach to reducing the environmental impacts associated with the building sector is the development and use of bio-based building materials. The objective of this study is to determine ...the water properties of bio-based insulation materials, derived from winegrowing co-products, which promote energy efficiency. The water performance of these new bio-based materials is based on the measurement of the moisture buffer value, the sorption isotherm, and the water vapor permeability. Four by-products are analyzed: stalks, grape pomace, crushed stalks, and skins; they are combined with a potato starch binder. The performance of these composites is compared to two other bio-based composites (hemp/starch and beet pulp/starch). The stalk/starch composite can be classified as a hygroscopic and breathable material with excellent moisture retention capacity.
In this article, Particle Image Velocimetry (PIV) experiments are carried out in an attempt to predict the morphology of fluid flow induced by natural convection in an Inclined PhotoVoltaic Double ...Skin Façade (IPVDSF) during transient and laminar regimes. These experiments were performed on an unevenly heated channel with an aspect ratio Ar = 5.2 and heated with UHF equal to 445 W/m
2
, corresponding to a modified Rayleigh number Ra
m
= 2.2 10
6
. It should be noted that the study is carried out under both realistic geometrical and environmental conditions. Seeking to simulate the impact of the surroundings, the unevenly heated channel is immersed within a water reservoir. Besides the investigations on fluid flow behavior, the purpose of this work is to plug the gap between baseline data to be used for numerical findings accuracy and the data helping in design development of such systems, while keeping in mind aesthetics as well as PhotoVoltaic (PV) efficiency enhancement aspects. The considered dispositions of the PVDSF duct are a negative slope (-10°) and positive slope (+ 10°), compared with the baseline case of vertical slope 0°. Results are described by streamlines and velocity field. The main observation is a complicated topological flow morphology within the PVDSF channel, but it should also be noted that the slope has a significant effect on flow and velocity fields for both flow regimes. Excellent agreement is finally found between the current experimental results and the theoretical ones.
(1) Background: Many studies suggest that migratory bird groups fly in a V-formation to improve their aerodynamic efficiency, the goal being to reduce their energy expenditure to fly longer ...distances. To further validate this hypothesis, we numerically simulated the aerodynamic interaction of two gliding migratory birds and evaluated the aerodynamic forces as a function of the bird spacing. (2) Methods: Computational Fluid Dynamics (CFD) was used to model the flow pattern in and around the wake of Canada geese flying at an altitude of 1000 m and a speed of 13.9 m/s. (3) Results: The post-processing of the 3D results revealed a complex flow structure composed of two contra-rotating vortices developing at the wing tip. (4) Conclusions: In a plane perpendicular to the main flow direction, we showed that the bird’s wake could be broken down into two distinct zones: the downwash zone and the upwash zone, the latter being used by birds flying in formation to reduce their energy expenditure. The results of our study suggested an optimal wingtip spacing of -26cm to maximize the lift/drag ratio that characterizes aerodynamic efficiency.
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