Search results for " sediment transport"
showing 10 items of 10 documents
Comparing two applicative criteria of the soil erosion physical model concept
2017
The physical model represented by a replicated plot has been suggested to be the best possible, unbiased, real world model to predict plot soil erosion. The aim of this investigation was to compare the original applicative criterion of the physical model concept proposed by Nearing with that later suggested by Bagarello et al. The comparison was performed by using three empirical soil erosion models (the Universal Soil Loss Equation [USLE], a modified USLE [USLE-MM], and the Central and Southern Italy [CSI] model) and plot soil loss data collected at the experimental station of Sparacia, in Sicily (southern Italy). The investigation showed that (i) the new criterion was generally more restr…
Modeling Bedload Transport Trajectories along a Sine-generated Channel
2019
This 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 develop…
Simulation of the operation of detention tanks.
2005
The performance of detention tanks with different characteristics (volume, on-line and off-line arrangement) has been evaluated according to the results of a continuous simulation. The conceptual simplified model for sewer system simulation (COSMOSS) model has been used to simulate the operation of the tanks. The differences between the performance of on-line and off-line tanks and the influence of the characteristics of different catchments have been examined. According to the results of the simulations detention tanks demonstrated good performances in total suspended solids retention and this evenience can certainly help to prevent water pollution of receiving water bodies in urban areas,…
Simulation of Sediment transport and flow characteristics downstream of a hydraulic structure
2016
The presence of a hydraulic structure (such as a dam) in a given river reach determines “constrained” sediment boundary conditions and thus transient transport phenomena. Many predictive mobile-bed one-dimensional models have been developed in or-der to predict sediment transport during transients but, even today, they have not attained a high degree of efficacy. This is because these models are confronted with some difficulties such as the reliable prediction of bed roughness or/and to the presence of flexible vegetation, of hydraulic sorting, of water-bed sediment interchanges in no-equilibrium situations. In the present work, with the aid of a 1-D numerical model previously developed (Te…
Evolution of coherent turbulent structures and relation with bed-forms formation in a straight flume
2008
The present paper describes some results of experimental work carried out in a rectilinear flume to investigate the interactions between flow turbulence and sediment motion. The analysis is conducted through the comparison between the periodicity of turbulent structures evolving along the channel and the wavelength of bed forms (alternate bars) forming on the bed. The occurrence of turbulent events (inward interaction, ejection, sweep and burst) has been verified through the conditioned quadrant analysis. The quantitative information about the spatial and temporal scale of the events has been obtained through the space-time correlations of the conditioned data. The analysis essentially high…
Experimental observation of horizontal coherent turbulent structures in a straight flume
2009
The present paper describes results of laboratory experiments carried out to investigate the evolution of horizontal coherent turbulent structures for different roughness conditions of channel walls. The occurrence of turbulent events (inward interaction, ejection, sweep and burst) is identified through the conditioned quadrant analysis. The filtered data set is used to determine the probability density distribution of each turbulent event. Particular attention is focused on sweep and ejection events and peculiar maps showing the distributions of the horizontal Reynolds shear stress, for each examined experimental condition, are also presented and discussed.
Modelling soil carbon fate under erosion process in vineyard
2017
Soil erosion processes in vineyards beyond water runoff and sediment transport have a strong effect on soil organic carbon loss (SOC) and redistribution along the slope. The variation of SOC across the landscape determines a difference in soil fertility and vine productivity. The aim of this research was to study erosion of a Mediterranean vineyard, develop an approach to estimate the SOC loss, correlate the vines vigor with sediment and carbon erosion. The study was carried out in a Sicilian (Italy) vineyard, planted in 2011. Along the slope, six pedons were studied by digging 6 pits up to 60cm depth. Soil was sampled in each pedon every 10cm and SOC was analyzed. Soil erosion, detachment …
Nonuniform sediment transport estimation in non-equlibrium situations: study cases
2014
EXPERIMENTAL ANALYSIS OF RELATION BETWEEN COHERENT TURBULENT STRUCTURES AND BED-FORMS FORMATION
2008
The present paper describes an experimental investigation on the interactions between flow turbulence and sediment motion. During the experiments, detailed measures of flow velocity components have been carried out using an Acoustic Doppler Velocimeter (ADV). The occurrence of turbulent events (inward interaction, ejection, sweep and burst) has been verified through the conditioned quadrant analysis. The quantitative information about the spatial and temporal evolution of turbulent events has been obtained through the space-time correlations of the conditioned data. As the primary objective was to analyse how turbulent structures influence the bed-forms formation, the spatial scale of turbu…