1,720,962 research outputs found
Sull' aspetto organizzativo del termalismo e sulla diffusione della didattica universitaria dell' Idrlogia Medica in diversi paesi del mondo
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Turbulent kinetic energy redistribution in a gravity current interacting with an emergent cylinder
No full textGravity currents are flows driven by density gradients between two or more contacting fluids and play a key role in nature and industrial environments via global ocean circulations, climate variability and the distribution of airborne pollutants. In the present work, we study, experimentally, the changes induced by an emergent vertical PVC cylinder on the mean and turbulent flow fields of an unsteady bottom-generated lock release gravity current. Tests were carried out, with and without the cylinder, in refractive index matching conditions and instantaneous velocities were acquired with a Particle Image Velocimetry system. The mean velocity field, Reynolds stresses and terms of turbulent kinetic energy (TKE) budget for the currents head were presented and discussed. The results show that the adverse pressure gradient generated by the cylinder induces a uniform deceleration of the current head. Hence, there are no appreciable differences on the spatial distribution of the mean velocities in the current head, compared to the undisturbed current. On the other hand, the changes on the turbulent flow field are remarkable. The total diffusion of TKE decays in the inner part of the head while becoming stronger at the interface between the two fluids, as the current approaches the cylinder. This is associated to an increase of the diffusion term due to pressure fluctuations, that acts against diffusion due to velocity fluctuations and contributes to disrupt the transport of TKE from the interface between the fluids and the inner part of the current. As a result, in the presence of an obstacle, Reynolds stresses are suppressed in the inner part of the current head and enhanced at the interface
Aquatic plants entrap different size of plastics in indoor flume experiments
No full textPlastics accumulate in the environment affecting biota and ecosystems. Although rivers are vectors of land-based plastics to the sea, macroplastics and microplastics in rivers are recently studied. Most studies focused on floating plastic transport to the sea through rivers considering only abiotic hydromorphological factors. In this view, among biotic factors, vegetation has recently been found to entrap plastics. Indeed, the role of vegetation is pivotal in affecting riverine plastic transport. While marine vegetation blocking plastics has been studied, research in freshwater ecosystems is neglected. Since hydrological factors have a pivotal role in riverine plastic transport and few is known on plant entrapment, the interaction between hydrological variables and plastic entrapment by vegetation has not yet been investigated. Given that the composition, transport, and fate of “submerged” plastics in the water column are neglected, we aimed at investigating the behaviour of plants in entrapping plastics within a specific laboratory flume tank. Specifically, we assessed whether (i) aquatic plants block different plastic sizes within the water column and (ii) different factors (e.g. water level, density of plants) affect plastic entrapment. Our results showed that, according to plant density, the higher the plant density the higher the entrapment of plastics by plants - independently of plastic size. Considering the water level, macro-, meso-, and microplastics were trapped similarly. Moreover, Potamogeton crispus blocked fewer microplastics compared with Myriophyllum spicatum. Our results might have impact as plants acted as temporary plastic trappers and can be used as tools for mitigating plastic pollution. Future research might investigate if this laboratory approach can be applied in field for recollecting plastics and consequently mitigating the problem. In conclusion, good management of plants in watercourses, canals, and rivers should be ideal for enhancing river functionality and ecosystem services for human well-being (i.e. the plastic entrapment service by plants)
Rilievi clinico-statistici circa l’indicazione di cure termali in soggetti controllati presso un centro ambulatoriale universitario
No full textOsservazioni circa i risultati di ricerche cliniche eseguite in corso di crenoterapia presso le Terme di Cotilia
No full textLock Release Gravity Current Interacting with a Cylindrical Obstacle
No full textThe interaction between a full-depth lock-release gravity current and an emergent vertical cylinder is experimentally studied by analyzing of the changes in the velocity field. Velocity measurements are taken in a vertical plane upstream the obstacle through a 2D Particle Image Velocimetry system. The study concerns the changes in the mean velocity field, Reynolds stresses and the turbulent kinetic energy production term induced by the presence of an adverse pressure gradient by comparing the data obtained in presence of an obstacle with those obtained in the configuration without it. The obstacle doesn’t induce changes in the mean flow, highlighting that the deceleration caused by the obstacle occurs in a uniform manner in the current. Instead, the spatial distribution of Reynolds stresses and consequently of the turbulent kinetic energy production is deeply affected by the obstacle. The increase in the adverse pressure gradient causes disruption of the transport from the major source of energy extraction to the backflow. Fluxes remain localized along the current front. This leads to a decay of turbulent kinetic energy within the current and its increase at the interface
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