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Upwelling processes bring nutrient-rich waters from the deep ocean to the surface. Areas of upwelling are often associated with high productivity, offering great economic value in terms of fisheries. The sensitivity of spring/summer-time coastal upwelling systems to climate change has recently received a lot of attention. Several studies have suggested that their intensity may increase in the future while other authors have shown decreasing intensity in their equatorward portions. Yet, recent observations do not show robust evidence of this intensification. The Senegalo-Mauritanian upwelling system (SMUS) located at the southern edge of the north Atlantic system (12°N–20°N) and most active in winter/spring has been largely excluded from these studies. Here, the seasonal cycle of the SMUS and its response to climate change is investigated in the database of the Coupled Models Inter comparison Project Phase 5 (CMIP5). Upwelling magnitude and surface signature are characterized by several sea surface temperature and wind stress indices. We highlight the ability of the climate models to reproduce the system, as well as their biases. The simulations suggest that the intensity of the SMUS winter/spring upwelling will moderately decrease in the future, primarily because of a reduction of the wind forcing linked to a northward shift of Azores anticyclone and a more regional modulation of the low pressures found over Northwest Africa. The implications of such an upwelling reduction on the ecosystems and local communities exploiting them remains very uncertain.

Abstract This work aims to predict the general performances of a pilot parabolic trough collector during transient periods. To do so, a one-dimensional thermal model has been developed. It has been validated with experimental results from two different experimental setups, in steady-state conditions, with a transmitted power maximum error of 3.4%. Since the model only predicts the collector's thermal behavior, the parabolic trough collector has been first optically qualified. Then, optical efficiencies were used as input for the model. Experimental results were obtained in steady-state conditions and compared to the model. Then, experimental and numerical results were compared during two period of time with varying inlet conditions (i.e. dynamic condition tests): the first one with stable conditions, and the other one with harsh conditions. The developed model showed a good capability of predicting the thermal behavior of the parabolic trough collector with unstable environment (DNI, mass flow, inlet temperature), with a 9.6% relative standard error in the worst case. As a conclusion, while previous studies only focused on steady-state conditions, it has been showed that this kind of model can be used to precisely predict the dynamic behavior of large power plants.

Abstract. An improved understanding of present-day climate variability and change relies on high-quality data sets from the past 2 millennia. Global efforts to model regional climate modes are in the process of being validated against, and integrated with, records of past vegetation change. For South America, however, the full potential of vegetation records for evaluating and improving climate models has hitherto not been sufficiently acknowledged due to an absence of information on the spatial and temporal coverage of study sites. This paper therefore serves as a guide to high-quality pollen records that capture environmental variability during the last 2 millennia. We identify 60 vegetation (pollen) records from across South America which satisfy geochronological requirements set out for climate modelling, and we discuss their sensitivity to the spatial signature of climate modes throughout the continent. Diverse patterns of vegetation response to climate change are observed, with more similar patterns of change in the lowlands and varying intensity and direction of responses in the highlands. Pollen records display local-scale responses to climate modes; thus, it is necessary to understand how vegetation–climate interactions might diverge under variable settings. We provide a qualitative translation from pollen metrics to climate variables. Additionally, pollen is an excellent indicator of human impact through time. We discuss evidence for human land use in pollen records and provide an overview considered useful for archaeological hypothesis testing and important in distinguishing natural from anthropogenically driven vegetation change. We stress the need for the palynological community to be more familiar with climate variability patterns to correctly attribute the potential causes of observed vegetation dynamics. This manuscript forms part of the wider LOng-Term multi-proxy climate REconstructions and Dynamics in South America – 2k initiative that provides the ideal framework for the integration of the various palaeoclimatic subdisciplines and palaeo-science, thereby jump-starting and fostering multidisciplinary research into environmental change on centennial and millennial timescales.

In order to know the origin of the noise generation when an impinging jet hit a specific geometry, an experimental setup was used allowing the generation of the flow and the adjustments of its parameters (such as Reynolds number, confinement, alignment, etc…). The vortex dynamics in case of a high acoustic level for two different Reynolds numbers Re = 5684 and Re = 6214 are considered here. Indeed, many configurations allow self-sustaining sound loop to take place in confined spaces between the nozzle and the impinged surface. This feedback loop optimizes the energy transfer between the aerodynamic field and the acoustic field and creates a source of noise that can become very noisy. Thus, to control these phenomena, it is necessary to understand the aero-acoustic coupling in such configurations. As a result, we measured the 2C kinematic instantaneous fields (vx, vy) of the flow by the technique of Particle Image Velocimetry (PIV) with a sampling rate of 1 KHz and the acoustic field is obtained using a B&K Microphone. For the two considered Reynold numbers, we can distinguish two patterns for the vortices travelling from the nozzle toward the plate of impact.

This paper details a numerical study of solid-liquid phase change heat transfer in a rectangular enclosure with the aim of optimizing the number, dimension, and positioning of fins in the enclosure. The enclosure is exposed on one side to a constant heat flux of 1000 W/m2 for 3 h and both the total fin mass and the PCM mass are kept constant in all simulated cases. The heat diffusion equation in the PCM uses the equivalent heat capacity method while natural convection driven PCM motion in the enclosure is modeled through the buoyancy force, using a modified viscosity and an additional volume force term in the Navier-Stokes momentum conservation equation. Three efficiency assessment parameters are used: (i) the height-averaged temperature of the front hot plate which should remain as low as possible for the longer possible time, (ii) the energy stored inside the PCM as a function of time, and (iii) the heat transfer rate and heat flux between the front plate and the PCM. For each simulated case, complementary data such as the standard deviation of temperature along the heated plate and the ratio of sensible heat to latent accumulation are also calculated. Results show that increasing the number of fins diminishes both the stabilization temperature and the stabilization time of the front plate during phase change, and accelerates the sensible and latent storage of energy in the PCM. Using thinner but longer fins provides the same impact except that the stabilization time also increases as the fin length is increased. Besides, at constant fin mass, varying fin spacing have marginal impact on the latent heat storage performance and on the hot plate temperature stabilization. The study also shows that the surface area plays the largest role in the increase of the heat transfer rate between the front plate and the PCM, while configurations which can promote stronger natural convection lead to higher heat flux. Finally, it was observed that systems allowing easier heat transfer to the back plate during melting provide a higher ratio of sensible heat to latent accumulation, while the standard deviation of the front plate temperature decreases as the number of fins or the spacing between fins increases.

In Western countries, the consumption of animal protein, which is the predominant protein source, has been decreasing over the last decade. This consumption has been negatively associated with different sustainability parameters in the majority of cases, and studies modelling sustainable diets have shown that the different parameters are not always compatible. Diets that significantly improve different sustainability parameters have been modelled, but the consideration of cultural acceptability is insufficient and requires further investigation. The objective of this thesis was to model acceptable trajectories of rearrangement of protein source consumption to increase nutritional adequacy and to evaluate its impacts on sustainability. The study of protein source consumption in France led to the conclusion that protein intake is adequate for the entire population, but that there are different profiles of protein intake characterized by different levels of nutritional security. A study conducted in 2018 found that meat consumption levels were predicted by attitudes, social norms, and perceived behavioral control related to the reduction of meat consumption. For the stepwise dietary modelling study, it was considered acceptable for an individual to consume a new food if it was widely consumed by individuals with a similar profile of protein intake. This hypothesis was validated by a survey conducted in 2018. The modelling work identified that some dietary recommendations were effective for the general population, but others were specific to certain profiles of protein intake characterized by specific nutritional profiles and food repertoires. Finally, models have identified that systematically targeting more plant proteins during the first dietary modifications allows, despite a slightly lower nutritional adequacy, to obtain better sustainability parameters.; Dans les pays occidentaux, la consommation de protéines animales, majoritaire, diminue depuis une décennie. Elle est, dans la majorité des cas, associée négativement à différents paramètres de durabilité, et les études modélisant des régimes durables ont montré que les différents paramètres n’étaient pas toujours compatibles. Des régimes améliorant largement différents paramètres de durabilité ont été modélisés, mais la prise en compte de l’acceptabilité culturelle est insuffisante et nécessite des approfondissements. L’objectif de cette thèse était de modéliser des trajectoires acceptables de réarrangement de la consommation de sources protéiques pour augmenter l’adéquation nutritionnelle et d’en évaluer les impacts sur la durabilité. L’étude des consommations de sources de protéines en France a permis de conclure que les apports en protéines sont adéquats pour l’ensemble de la population, mais qu’il existe différents profils de consommation protéique, caractérisés par des niveaux de sécurité nutritionnelle différents. Une étude réalisée en 2018 a permis d’établir que les niveaux de consommation de viande étaient prédits par les attitudes, les normes sociales, et l’auto-efficacité perçue vis-à-vis de la réduction de la consommation de viande. Pour les travaux de modélisation pas-à-pas de l’alimentation, il a été considéré acceptable pour un individu de consommer un nouvel aliment, si celui-ci était largement consommé par des individus au profil de consommation protéique similaire. Cette hypothèse a été validée par une enquête en 2018. Les travaux de modélisation ont permis d’identifier que certaines recommandations alimentaires étaient efficaces pour l’ensemble de la population, mais que d’autres étaient spécifiques à certains profils de consommation protéique, caractérisés par des profils nutritionnels et des répertoires alimentaires spécifiques. Enfin, des modèles ont permis d’identifier que viser systématiquement plus de protéines végétales lors des premières modifications diététiques permet, malgré une adéquation nutritionnelle légèrement plus faible, d’obtenir de meilleurs paramètres de durabilité.