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Didkovskyi Oleksandr Ivanov Vladislav Radice Alessio Papini Monica Longoni Laura Menafoglio Alessandra 《Mathematical Geosciences》2022,54(3):467-506
Mathematical Geosciences - The problem of providing data-driven models for sediment transport in a pre-Alpine stream in Italy is addressed. This study is based on a large set of measurements... 相似文献
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Results are presented for a long-duration sediment transport experiment with a plane bed. High-frequency time series of sediment
concentration, sediment velocity and solid discharge per unit width were measured using image analysis of video records. A
range of transport intensities from a single experiment has been analysed considering transport at different distances from
the sidewalls as an independent variable. First and second order temporal statistics of the spatially-averaged values of the
transport parameters are presented, which are in agreement with previous studies. A refined statistical analysis of the sediment
concentration dynamics, reflecting bed load process, is also given. The characteristic scales of the sediment concentration
dynamics are evaluated and analyzed in conjunction with those of the near-bed and bulk flow fields. 相似文献
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The sediment transport process on a flat bed was investigated experimentally, with reference to the relationship between the
average solid discharge and the concentration and velocity of the moving grains. The instantaneous values of the quantities
were measured and, therefore, it was possible to quantify the contribution of the temporal fluctuations of concentration and
velocity to the resulting average sediment transport rate. Recognizing that the sediment transport process is an episodic
phenomenon, an intermittency factor was defined and its contribution to the solid discharge, typically implicit in earlier
formulations of the sediment flux, was highlighted. Conceptual analyses of the spatial scale dependence of the quantities
were also made. 相似文献
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Troy A. Henderson John L. Junkins Gianmarco Radice 《Celestial Mechanics and Dynamical Astronomy》2009,104(4):355-368
A complex exponential solution has been derived which unifies the elliptic and hyperbolic trajectories into a single set of
equations and provides an exact, analytical solution to the unperturbed, Keplerian two-body problem. The formulation eliminates
singularities associated with the elliptic and hyperbolic trajectories that arise from these orbits. Using this complex exponential
solution formulation, a variation of parameters formulation for the perturbed two-body problem has been derived. In this paper,
we present the analytical formulation of the complex exponential solution, numerical simulations, a comparison with classical
solution methods, and highlight the benefits of this approach compared with the classical developments.
Previously presented as AAS 07-136 at the 17th AAS/AIAA Spaceflight Mechanics Meeting Sedona, Arizona, AAS 08-206 and AAS
08-230 at the 18th AAS/AIAA Spaceflight Mechanics Meeting Galveston, Texas. 相似文献
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Camilla Colombo Massimiliano Vasile Gianmarco Radice 《Celestial Mechanics and Dynamical Astronomy》2009,105(1-3):75-112
In this paper an optimisation algorithm based on Differential dynamic programming is applied to the design of rendezvous and fly-by trajectories to near Earth objects. Differential dynamic programming is a successive approximation technique that computes a feedback control law in correspondence of a fixed number of decision times. In this way the high dimensional problem characteristic of low-thrust optimisation is reduced into a series of small dimensional problems. The proposed method exploits the stage-wise approach to incorporate an adaptive refinement of the discretisation mesh within the optimisation process. A particular interpolation technique was used to preserve the feedback nature of the control law, thus improving robustness against some approximation errors introduced during the adaptation process. The algorithm implements global variations of the control law, which ensure a further increase in robustness. The results presented show how the proposed approach is capable of fully exploiting the multi-body dynamics of the problem; in fact, in one of the study cases, a fly-by of the Earth is scheduled, which was not included in the first guess solution. 相似文献
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Molinari Daniela Dazzi Susanna Gattai Edoardo Minucci Guido Pesaro Giulia Radice Alessio Vacondio Renato 《Natural Hazards》2021,108(3):3061-3084
Natural Hazards - This paper shows a detailed, advanced procedure to implement cost–benefit analyses (CBAs) in order to assess the effectiveness of flood mitigation measures. The town of Lodi... 相似文献
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Scale-based statistical analysis of sediment fluxes 总被引：1，自引：1，他引：0
The flux of sediments over a line perpendicular to the main flow direction was measured during experiments of weak one-dimensional bed load. The standard definition of solid discharge through a boundary is a straightforward issue, yet the dependence of resulting values on the spatial and temporal scales used as a support for measurement is not. In this work, first- and second-order statistics of sediment transport rates were analyzed as scale-dependent quantities. The spatial scales used were significantly larger than the particle size, while the temporal scales covered a two-orders-of-magnitude range enabling the physical time scales of the single particles to be appreciated. In addition, the relationship between sediment fluxes, process intermittency and particle interarrival times was investigated. Proper knowledge of the scale-dependence of statistical properties of sediment transport fluxes may allow for adequate design of measuring campaigns (both in the laboratory and field) and for sound interpretation of data from multiple sources. 相似文献
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Understanding coarse sediment transport is crucial for the prediction of sediment migration and the consequent development of fluvial morphologies. In this study, cobble displacements in a pre-Alpine creek have been recorded by means of radio frequency identification (RFID). Pebble monitoring has been systematically performed after each rainfall event with moderate precipitation, in order to exclude the superimposition of sediment displacements induced by triggering factors acting at different times. The analysis of the collected data was carried out through the application of both a principal component analysis and the Buckingham Π theorem. The experimental trends were interpreted considering the ratio of mobile pebbles, the pebbles' displacement and virtual velocity as the dependent variables. These quantities mostly depend on the event peak discharge, with a nonlinear increase of the travelled distance and a growth of up to two orders of magnitude of the virtual velocity (for an approximately 10× increase in peak discharge). An inverse dependency of the virtual velocity on the event duration was also observed. A comparison of the results obtained with those from laboratory investigations of bedload transport mechanics evidenced the differences in parametric trends associated with sediment mobility in the two environments. This contrast brings forward the combination of multiple drivers of sediment mobility, such as local morphology, sediment dimensions and flow unsteadiness, warranting a further in-depth investigation. Representation of results in a dimensionless form is suggested as a good practice to analyse data from case studies characterized by different scales. © 2019 John Wiley & Sons, Ltd. 相似文献
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