1,720,997 research outputs found
Use of Vegetation as Biomaterial for Controlling Measures of Human Impact on the Environment
Full text linkIn a context of a climate change, bioengineering techniques and biomaterials are needed to reduce the human impact on the environment. Thus, in recent years, living materials have been used in environmental engineering applications. In the present paper, attention is restricted to the vegetation, and a brief review on its use as biomaterial in engineering control techniques is presented. The core of this review is a comprehensive overview of two important techniques using vegetation as living material for measures limiting the human impact both in extra-urban and in urban sites. In particular, the use of vegetation both as living material for soil erosion protection and river's bank stabilization in extra-urban areas and as a part of green roofs or walls added to buildings in urban areas is presented. Considerations about the advantages and disadvantages of these techniques conclude this review
SAFETY COVER HYDRO-PV Dispositivo domotico multifuzione per la manutenzione e la sicurezza dei pannelli fotovoltaici con aumento dell’efficienza e della durabilità del sistema
No full textCon l’aumento dell’uso dell’energia solare, sia in ambito civile che in ambito industriale, diventa sempre più importante il problema della manutenzione e della gestione dei pannelli fotovoltaici.Il dispositivo Safety Cover Hydro - PV, ideato e brevettato dai membri dalla Safety Environmental Engineering (spin-off dell’Università degli Studi di Palermo che opera nell’ambito della Sicurezza Ambientale) consente di superare tali limit
Turbulent mixing and dispersion mechanisms over flexible and dense vegetation
No full textThe present study investigates flow turbulence and dispersion processes in the presence of flexible and dense vegetation on
the bed. The turbulent dispersion coefficients and the terms of the turbulent kinetic energy equation are determined by using
data collected in a straight laboratory channel with living vegetation on the bed. Results show that the turbulent integral
lengths assume an order of magnitude comparable to the stems’ characteristic dimension independently by the direction
and the turbulence assumes an isotropic behavior. The coefficients of dispersion have a trend similar to that of the turbulent
lengths and assume low values in the longitudinal, transversal and vertical directions. Results also show that, in the mixing
layer, the shear and wake turbulence production terms balance the dissipation; the turbulent diffusion term also assumes low
values and its sign varies along the vertical indicating a transport of turbulent energy both from the vegetation to the free
surface and from the free surface to vegetation
Experimental analysis of the effect of non-uniform submerged vegetation on flow characteristics at the apex section of a meandering laboratory flume
No full textKEY POINTS
• Flow characteristics at the apex section of a large amplitude meandering flume with and without of patches of flexible vegetation
• Effect of patches of flexible vegetation on flow characteristics
• Analysis of the effects of the vegetated stems fluctuation in the transitional area between vegetated and non-vegetated zone
Velocity distribution and Dip phenomenon in a large amplitude meandering channel
No full textThe prediction of the velocity-dip, whereby the location of the maximum velocity occurs below the water surface, could be important for defining the flow pattern and the momentum transport processes. This study explores the dip-phenomenon in a high-curvature meandering bend. With the aid of data collected in a laboratory flume, the influence of the distance to the outer bank, the channel's curvature and the aspect ratio on the formation and position of the velocity-dip is investigated. Results show that, for the aspect ratios examined, a dip forms in the velocity profiles and its position varies along the bend as a function of the channel's curvature and the aspect ratio. Based on the measured data, an equation relating the velocity-dip to the local deflection angle, theta, and the width-to-depth ratio B/h(av) is presented. It has been verified that the values of the velocity-dip estimated by the presented equation are in good agreement with the experimental one
Modeling Bedload Transport Trajectories along a Sine-generated Channel
No full textThis study explores the influences of flow discharge and particle size on bedload transport trajectory
by applying a depth-averaged two-dimensional model to a 110° sine-generated laboratory flume with
wide-and-shallow sections. Calculated results exhibit two erosion regions in a bend: Zone-1 ‒ foreside of the
point bar near the convex bank and Zone-2 ‒ near the apex of the concave bank. Sediments eroded from
Zone-1 are mainly transported along the same-side convex bank rather than crossing the channel centerline,
indicating the crucial role of longitudinal flow in shaping point bars. Most particles from Zone-2, however,
behave more complicated by changing their trajectories with the developing bar-pool topography. Besides,
sensitivity analyses indicate that, the shifting of bedload trajectory in the curved channel is not susceptible to
particle size while considerably varies with flow discharge. Moving particles in a meandering channel are ultimately
constrained within the belt of “concave bank‒crossing bar‒concave bank” after the bend topography
is fully developed and the bed deformation reaches a dynamic equilibrium
Experiments on Longitudinal and Transverse Bedload Transport in Sine-Generated Meandering Channels
Full text linkBedload grains in consecutive meandering bends either move longitudinally or across the channel centerline. This study traces and quantifies the grains’ movement in two laboratorial sine-generated channels, i.e., one with deflection angle θ0 = 30° and the other 110°. The grains originally paved along the channels are uniform in size with D = 1 mm and are dyed in various colors, according to their initial location. The experiments recorded the changes in the flow patterns, bed deformation, and the gain-loss distribution of the colored grains in the pool-bar complexes. We observed the formation of two types of erosion zones during the process of the bed deformation, i.e., Zone 1 in the foreside of the point bars and Zone 2 near the concave bank downstream of the bend apexes. Most grains eroded from Zone 1 are observed moving longitudinally as opposed to crossing the channel centerline. Contrastingly, the dominant moving direction of the grains eroded from Zone 2 changes from the longitudinal direction to the transversal one as the bed topography evolves. Besides, most building material of the point bars comes from the upstream bends, although low- and highly curved channels behave differently
Effect of vegetation on Mixing and Dispersion Processes at the apex section of a meander bend
Full text linkAquatic vegetation exerts a strong influence on the fluvial ecosystem. Understanding flow characteristics and turbulent structure in the presence of vegetation is especially important with respect to environmental processes as sediment transport and mixing of transported quantities. In the present paper attention is focused on the kinematic and mixing processes in the presence of flexible submerged vegetation on the bed of a curved channel. In particular, the effect of vegetation on the flux of mass distribution and on the transport process at the apex section of a meandering bend is investigated by comparing the distributions of the dispersion coefficient estimated in vegetated areas and in no-vegetated ones
Flow Velocity and Turbulence Structure in gravel-bed rivers: experimental investigation in a straight laboratory flume
No full textGravel-bed flows are characterized by complex fluid/bed interactions. The presence of gravels on the bed determines spatial heterogeneities of flow velocity and turbulence structure. In this paper, experimental data collected in a gravel-bed straight laboratory channel are analyzed in order to evaluate the effect of the bed roughness on the velocity and the turbulence intensity profiles. Results show that gravel inflects the velocity distribution near the bed creating an S-shaped profile. The experimental velocity distributions are positively compared with the hyperbolic tangent profile of a pure mixing layer previously tested in vegetated flows. It has been verified that the averaged turbulence intensity profiles have a maximum at a relative water depth which approximately corresponds to that of the inflection point of the averaged velocity profiles
Morphodynamics of the Parana River in the light of climate change
No full textThe work highlights the sediment dynamics that takes place at different scales along the Middle and Lower Parana River (Argentina), by means of different numerical models. The principal aim of this study is to provide a multi-disciplinary and multi-scale approach to predict the future river’s morphodynamics in the light of climate change. This approach may be applied to evaluate the long-term impact of the river’s morphodynamics on anthropogenic structures and activities over or nearby the watercourse (i.e., bridges, levees, navigation way). The study was realized by using three different levels of detail of mathematical modelling. Climate models give the input ensemble, i.e., future precipitation and temperature over the La Plata Basin. The VIC hydrological model simulated the flow discharge time-series, which were then used as input for an own-developed 1-D hydro-morphodynamic model. This 1-D code was able to simulate future rate of sediment transport and corresponding bed-level changes at watershed scale and provided the initial and the boundary conditions for a more detailed 2-D model. Therefore, future evolutions of a specific part of the main and the secondary channels were simulated with the MIKE21C code, developed by the Danish Hydraulic Institute.
The performed analysis indicated a rather low sensitivity of the Middle and Lower Parana River bed profile to the relevant increase forecasted in flow discharge, whereas the channels appreciably divagates. In particular, variability increase rather than averaged value of predicted discharges appeared effective in driving current bifurcated morphology into a meandering-multithread pattern
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