Sedimentation in the Three Gorges Reservoir (TGR) has been studied with a primary focus on the amount due to the decrease in sediment inflow caused by water and soil conservation projects and sediment retention of recently constructed upstream cascade reservoirs. In this study, the rate and distribution of sedimentation in the TGR were investigated. A total of 1.6 billion tons of sediment was trapped in the TGR from 2003 to 2015. The sediment retention rate increased from 60% during the initial operation stage between 2003 and 2005 to 82% during the normal operation stage between 2006 and 2015. Sediment finer than 0.008 and 0.016 mm contributed 44 and 61% of the total sedimentation, respectively, and the median size of the sedimentation was 0.01 mm. The spatial distribution of the sedimentation was discontinuous, and 80% of the sedimentation occurred in one-third of the backwater region, with primary deposition zones being at the wide reservoir reaches. The sedimentation was assessed by the sediment transport capacity, which was embedded in the 1-D sediment transport and bed deformation equations. Due to the impoundment of the TGR, the sediment transport capacities decreased significantly at the wide reservoir reaches where flocculation occurred, resulting in deposition. However, the sediment transport capacities were still greater than the sediment concentrations at the gorges, which will be the fixed stretches with no deposition. The surplus sediment transport capacity at the gorge stretches would not allow cumulative sedimentation in the future, leading to a spatially discontinuous equilibrium sedimentation along the TGR instead of the predicted spatially continuous distribution. A uniform bed slope is not expected under the new sedimentation equilibrium state, and the actual sedimentation will be considerably less than the initially predicted value, generating a sustainable storage volume with about 84.7% of the initial volume, which will facilitate the engineering functions of the TGR significantly.

This study experimentally examined the turbulent characteristics of decelerating open-channel flow based on particle imaging velocimetry measurement. The decelerating flow shows a similar velocity profile to that in uniform flow, but it exhibits greater turbulence intensity and Reynolds stress. Statistical evidence of the presence of very-large-scale motions (VLSMs) in decelerating open-channel flows was presented for the first time. The results indicate that VLSMs in decelerating flows can survive further away from the wall when compared to other wall-turbulence flows. The contribution rate of the VLSMs to the turbulent kinetic energy and the Reynolds stress in the decelerating open-channel flow is slightly lower than that in channels, boundary layers, and pipe flows.

The problem of liquid sloshing is widespread in the field of naval architecture and ocean engineering. During the sloshing process, the liquid will produce a large slamming force on the bulkhead. At the same time, the coupled sloshing of the liquid in tank and the hull will also affect the floating state and stability of the hull, and even induce safety accidents. The tank sloshing simultaneous with baffles and under rolling excitation is particularly focused in this paper, which is rarely concerned preciously. Based on the theory of fluid dynamics, the program of tank sloshing under large-amplitude rolling conditions by the smoothed particle hydrodynamics method is compiled, and the accuracy of the numerical model is validated through existing experimental results. Furthermore, the slamming pressure and the wetted height of the tank wall are studied for the cases of different excitation amplitudes and excitation frequencies. Then, the dynamic response characteristics of the sloshing tank with vertical and horizontal baffles are studied, and the effects of different baffle lengths are analyzed. The result shows that under rolling excitation the vertical baffle longer than the water depth can mitigate sloshing to some extent, but the vertical baffle whose length is less than the water depth and the horizontal baffles cannot play a role in mitigating the sloshing.

When benthic fish engage in predation, they often swim near the riverbank or close to hard rocks, where they are subjected to the combined effects of side and benthic walls. This study focuses on the brown trout and employs a three-dimensional numerical model to simulate the process of brown trout accelerating from a stationary state to a cruising state under the influence of wall effects. A self-developed subroutine algorithm is applied to solve the various hydrodynamic parameters of brown trout swimming. By varying the distance between the fish's center of gravity and the wall, this study explores the self-propelled performance and efficiency of fish swimming affected by the sidewall as well as the combined influence of the side and benthic walls. This study also reveals the hydrodynamic mechanism of wall effects that impact the performance of fish swimming in the body/caudal fin (BCF) mode. The results demonstrate that when the distance is less than 0.5 times the body length of the fish, swimming near the sidewall can enhance speed and thrust, but the swimming efficiency will reduce. Closer proximity to the benthic wall leads to increased power consumption and decreased efficiency, which is disadvantageous for fish swimming. The findings of this study reveal the unstable wall effects experienced by fish and offer insights for designing biomimetic underwater vehicles that leverage wall effects as well as for creating habitats that support fish swimming in the BCF mode.

Rough-bed open-channel flows (OCFs) are ubiquitous in rivers and canals. However, the scaling and energy contents of very-large-scale motions (VLSMs) in such flows remain unclear. In this study, the above characteristics of VLSMs are experimentally investigated with the measurement of particle imaging velocimetry (PIV). VLSM wavelengths obtained via premultiplied spectra analysis were consistent with previously reported values. Comparisons with these studies ruled out the role of relative submergence, and suggested that the channel aspect ratio is key to controlling the VLSM wavelengths in OCFs. VLSMs carry approximately 60% of the turbulence kinetic energy (TKE) and 38–50% of the Reynolds stress in rough-bed OCFs. The VLSM-related TKE fraction in the 0.1–0.5H range increased with increasing friction Reynolds number, while variation in the Reynolds shear stress did not exhibit any explicit trend.

The acoustic method, which enables continuous monitoring with great temporal resolution, is an alternative technique for detecting bedload movement. In order to record the sound signals produced by the impacts between gravel particles and detect the bedload motion, in this study, a hydrophone is placed close to the riverbed at the upper Yangtze River. Three categories of raw audio signals—moving gravel particles, ship engines, and flow turbulence—are collected and investigated. Signal preprocessing is performed using spectral subtraction to reduce the noise of the background sound, and the sound signal characteristic parameters are then calculated. In this paper, we propose a novel method for detecting and extracting bedload motion parameters, including peak frequency, pitch frequency, and energy eigenvector. When a segment of a speech signal meets the indicators for all three feature parameters simultaneously, the segment signal is classified as a bedload motion sound signal. Further work will be conducted to investigate bedload transport using the extracted audio signal.