AbstractA common approach used to mitigate riverbank erosion and maintain watercourse alignments has been through the application of riprap or larger, more stable particles to channel boundaries ...along reaches of interest. However, very often, these large particles become dislodged from their intended locations (failed erosion measures), becoming part of the bed material composition. In natural systems, large immobile sediments or boulders can also be found, which are often sourced from glacial erratics or colluvial inputs with different spacing and arrangements among them. In lower gradient gravel-bed channels, the impacts that large clasts may impart on river morphologies are uncertain and are studied in this paper. This paper utilizes laboratory experiments to evaluate the effects that varying spacing of large immobile particles in a gravel-bed channel have on sediment transport and bed morphology. The laboratory experiments consist of a series of test cases with a varying spacing of large immobile particles and one base case with no large immobile particles present. In each case, the flume bed was composed of a poorly sorted gravel mixture with a bimodal distribution of sand and gravel meant to be representative of a natural gravel-bed channel. The results of the test cases demonstrated that at a low spacing of large immobile particles, the transported material and the bed material both became coarser. At a medium spacing of large immobile particles, the bed material size and erosion reached a maximum, and the coarser bed material was transported at approximately the same rate as the finer material. Finally, at a high spacing of large immobile particles, the size of the transported material and bed material sizes were similar to that of the base case, and the sediment transport also had the strongest clockwise hysteresis trend, which ultimately led to a net erosion of the gravel-bed channel.
The artificial replenishment of sediment is used as a method to re-establish sediment continuity downstream of a dam. However, the impact of this technique on the hydraulics conditions, and resulting ...bed morphology, is yet to be understood. Several numerical tools have been developed during last years for modeling sediment transport and morphology evolution which can be used for this application. These models range from 1D to 3D approaches: the first being over simplistic for the simulation of such a complex geometry; the latter requires often a prohibitive computational effort. However, 2D models are computationally efficient and in these cases may already provide sufficiently accurate predictions of the morphology evolution caused by the sediment replenishment in a river. Here, the 2D shallow water equations in combination with the Exner equation are solved by means of a weak-coupled strategy. The classical friction approach considered for reproducing the bed channel roughness has been modified to take into account the morphological effect of replenishment which provokes a channel bed fining. Computational outcomes are compared with four sets of experimental data obtained from several replenishment configurations studied in the laboratory. The experiments differ in terms of placement volume and configuration. A set of analysis parameters is proposed for the experimental-numerical comparison, with particular attention to the spreading, covered surface and travel distance of placed replenishment grains. The numerical tool is reliable in reproducing the overall tendency shown by the experimental data. The effect of fining roughness is better reproduced with the approach herein proposed. However, it is also highlighted that the sediment clusters found in the experiment are not well numerically reproduced in the regions of the channel with a limited number of sediment grains.
The movement of poorly sorted material over steep areas constitutes a hazardous environmental problem. Computational tools help in the understanding and predictions of such landslides. The main ...drawback is the high computational effort required for obtaining accurate numerical solutions due to the high number of cells involved in the calculus. In order to overcome this problem, this work proposes the use of GPUs for decreasing significantly the CPU simulation time. The numerical scheme implemented in GPU is based on a finite volume scheme and it was validated in previous work with exact solutions and experimental data. The computational cost time obtained with the Graphical Hardware technology, GPU, is compared against Single-Core (sequential) and Multi-Core (parallel) CPU implementations. The GPU implementation allows to reduce the computational cost time in two orders of magnitude.
•A GPU implementation of a FV method for geophysical shallow flows is presented.•The GPU implementation has been performed over unstructured meshes.•The GPU implementation allows to reduce in two orders of magnitude the computational cost.•Real and up-to-date environmental problems are now affordable without the necessity of using coarse meshes.
•The formulation of an appropriate and self-stable coupling of numerical schemes for two-dimensional transient flows over heterogeneous erodible beds.•The numerical results are satisfactorily ...compared with 1D academic test cases and 2D experimental data. All of the cases studied are transient.•It is shown that the adequate evaluation of the sediment transport fluxes for each fraction provide a correct estimation of the bed and surface texture, in terms of spatial and temporal evolution.
In order to study the morphological evolution of river beds composed of heterogeneous material, the interaction among the different grain sizes must be taken into account. In this paper, these equations are combined with the two-dimensional shallow water equations to describe the flow field. The resulting system of equations can be solved in two ways: (i) in a coupled way, solving flow and sediment equations simultaneously at a given time-step or (ii) in an uncoupled manner by first solving the flow field and using the magnitudes obtained at each time-step to update the channel morphology (bed and surface composition). The coupled strategy is preferable when dealing with strong and quick interactions between the flow field, the bed evolution and the different particle sizes present on the bed surface. A number of numerical difficulties arise from solving the fully coupled system of equations. These problems are reduced by means of a weakly-coupled strategy to numerically estimate the wave celerities containing the information of the bed and the grain sizes present on the bed. Hence, a two-dimensional numerical scheme able to simulate in a self-stable way the unsteady morphological evolution of channels formed by cohesionless grain size mixtures is presented. The coupling technique is simplified without decreasing the number of waves involved in the numerical scheme but by simplifying their definitions. The numerical results are satisfactorily tested with synthetic cases and against experimental data.
Dense granular flows are present in geophysics and in several industrial processes, which has lead to an increasing interest for the knowledge and understanding of the physics which govern their ...propagation. For this reason, a wide range of laboratory experiments on gravity-driven flows have been carried out during the last two decades. The present work is focused on geomorphological processes and, following previous work, a series of laboratory studies which constitute a further step in mimicking natural phenomena are described and simulated. Three situations are considered with some common properties: a two-dimensional configuration, variable slope of the topography and the presence of obstacles. The setup and measurement technique employed during the development of these experiments are deeply explained in the companion work. The first experiment is based on a single obstacle, the second one is performed against multiple obstacles and the third one studies the influence of a dike on which overtopping occurs. Due to the impact of the flow against the obstacles, fast moving shocks appear, and a variety of secondary waves emerge. In order to delve into the physics of these types of phenomena, a shock-capturing numerical scheme is used to simulate the cases. The suitability of the mathematical models employed in this work has been previously validated. Comparisons between computed and experimental data are presented for the three cases. The computed results show that the numerical tool is able to predict faithfully the overall behavior of this type of complex dense granular flow.
AbstractIntense transient shallow flows over erodible bed imply the appearance of a changing horizontal density attributable to the presence of sediment particles in the water layer. The lack of ...consideration of the variability of the bulking density of the mixture is not admissible when modeling severe types of erosional flow such as the release of a dam break wave over a sedimentary bottom. Such events can lead to significant changes in the wave hydrodynamics, since the inertia of the flow can be larger and consequently its erosion/deposition capacity can be altered. From a numerical point of view a new complex erosion/deposition source term appears. For the integration of these source terms two strategies have been explored in this work: upwind and pointwise. Hence, this work is focused on the development and validation of a novel numerical scheme based on an approximate augmented Riemann solver, where the erosion/deposition rates play an important role in the variation of mixture density. Several analytical test cases have been derived in order to validate the computational tool. The numerical predictions have also been compared against experimental data.
The scattering through a Josephson junction (JJ) interrupting a superconducting line is revisited including power leakage. We also discuss how to make tunable and broadband resonant mirrors by ...concatenating junctions. As an application, we show how to construct cavities using these mirrors, thus connecting two research fields: JJ quantum metamaterials and coupled-cavity arrays. We finish by discussing the first nonlinear corrections to the scattering and their measurable effects.
•Frequency analysis and wavelet reconstruction techniques are suitable for the analysis of non-linear and non-stationary processes of badlands catchments.•Intra-annual and annual time scales are led ...by climatological characteristics of the catchment site.•Multi-year sediment yield response is linked with the intrinsic sediment storage/depletion cycle of the catchment.
A long-term database with information on precipitation, discharge and sediment yield dynamics was analyzed to characterize the temporal structure response of a catchment in a humid mountain badland area. Due to the non-linearity and non-stationary nature of the data, a combination of frequency analysis and wavelet reconstruction techniques were initially used to determine the dominant time scales of the precipitation, discharge and sediment yield. Within the full spectrum of time scales, the spectral frequency analysis could distinguish the dominant ones governing the overall trend of the time-series. Furthermore, the temporal multiresolution wavelet technique enabled accurate de-noising of the hydrometric and sediment time-series, by filtering out the high frequency intermittent processes superimposed on the main signal. Geomorphological metrics were subsequently applied to the filtered data and link to the temporal structure of the catchment response. The combined frequency-geomorphological analysis provides a physical explanation of the complete temporal structure of the catchment response to precipitation. This analysis features components from intra-annual, annual and multi-year scales. Intra-annual and annual time scales are led by climatological characteristics of the catchment site (seasonal rainfall patterns of a mountain Pyrenean catchment). The multi-year response related to the sediment yield reveals the importance of the sediment storage/depletion cycle in the catchment: although the main driver of the sediment yield is the discharge, weathering processes and sediment storage are also major control factors. Therefore, correct management of the catchment requires the combined multi-temporal response of water and sediment fluxes to be controlled. The temporal spectral analysis herein outlined provides a detailed analysis of the long-term temporal structure of databases and can be accepted as an adequate tool for catchment management in terms of flood forecasting or reservoir operation.
Background and ImportanceGeriatric community is the main group of patients affected by oropharyngeal dysphagia. In these population, numerous pharmaceutical forms need to be handled for subsequent ...administration. However, this manipulation can compromise the drug´s safety and efficacy.Aim and ObjectivesTo analyse the interventions for the adaptation of pharmacological treatment in nursing home (NH) patients with dysphagia.Material and MethodsAn observational, retrospective and descriptive study was carried out in two NH from June 2023 to September 2023. All patients with medication crushed were identified with the collaboration of the nursing staff. Biodemographic data, prescribed medications and the suggested interventions were recorded. The DEGLUFARM® guide was used for the interventions performed. The prescribing clinicians were notified.Results184 NH patients were included in our study. 60 of them (32.61%) had their medication crushed. Of these, 19 were male (31.67%) and 41 female (68.33%) with a median age of 86 years (ages ranging from 38 to 100 years). A total of 509 oral medications were analysed, with a median of 9 drugs per patient. Of all prescribed medications, 23 conflicting drugs prescribed in 20 patients were identified (33.33% of the patients who had their medication crushed).According to ATC classification, the most common conflicting drugs were: 6 Alpha-adrenoreceptor antagonists (26.09%), 3 drugs for constipation (13.04%) 3 antidepressants (13.04%), and 2 anticholinesterases (8.70%). The pharmaceutical forms that sholud not be crushed were: 8 retard tablets (34.78%), 5 gastroresistant tablets (21.74%), 5 retard capsules (21.74%) 4 coated tablets (17.39%) and 1 capsule containing gastrorresistant pellets (4.43%).The prescribing physician was notified in all cases, with the following proposals: 12 changes to a different active ingredient (52.17%), 10 changes to a different pharmaceutical form with the same active ingredient (43.48%) and 1 proposal for withdrawing due to a negative benefit-risk balance (4.35%).Conclusion and RelevanceHigh percentage of pharmaceutical forms that sould not be manipulated is prescribed in NH patients who have their medication crushed due to dysphagia Most of the proposed changes involve changes in active ingredients, so further clinical monitoring can be important. The pharmacists are qualified to carry out this type of intervention, improving the efficacy and safety of pharmacological treatments.References and/or AcknowledgementsConflict of InterestNo conflict of interest.
Soil erosion has reemerged as an environmental problem associated with climate change that requires the help of simulation tools for forecasting future consequences. This topic becomes even more ...relevant in Mediterranean catchments due to the highly variable and irregular rainfall regime. Hence, an approach that includes the rainfall/runoff and erosion phenomena is required for quantifying the amount of soil the catchments are transferring to the rivers. As the calibration process of the infiltration and erosion parameters can become cumbersome in terms of iterations to the optimal values to fit experimental data, a Simplified Catchment Model (SCM) is introduced as a first approach. The set of tuning constants that provides the best fit are used as input for re-calibrating the parameters by means of the simulation of the real catchment. The modeling effort here presented opens its application to the analysis of the hydro-sedimentary processes at larger temporal and spatial scales.
PDF
