Search

Rock weirs, typically created by the placement of loose rocks, are eco-friendly hydraulic structures used for raising the upstream water level, which has benefits for irrigation, shipping, and grade control. Although rock weirs are frequently submerged in rivers, few studies have systematically investigated their impacts on the upstream water level under submerged conditions. A series of flume experiments regarding this topic were conducted. Different flow discharges, tail-water depths, and void ratios were adopted in the experiments. The results show that (1) the submerged rock weirs primarily function to raise the upstream water level, while having a limited impact on the tail-water level; (2) for a given tail-water depth and void ratio, the upstream water level rise increases with increased discharge, although this response becomes insignificant as tail-water depth increases; (3) as void ratio increases, the upstream water level rise is expected to decrease for a given tail-water depth and discharge; and (4) based on the data and observations, a predictor including the effects of Froude number, submergence, and void ratio is proposed for estimating the upstream water level rise of submerged rock weirs. These results contribute to further understanding the hydraulic properties of rock weirs and are important for river training practices using rock weirs. [ABSTRACT FROM AUTHOR]

Bedload sediment transport plays an important role in the evolution of rivers, marshes and deltas. In these aquatic environments, vegetation is widespread, and plant species have unique morphology. However, the impact of real plant morphology on flow and sediment transport has not been quantified. This study used model plants with real plant morphology, based on the aquatic species Phragmites australis, Acorus calamus and Typha latifolia. The frontal area of these species increases away from the bed, which leads to higher near‐bed velocity than would be predicted from depth‐average frontal area. A plant morphology coefficient was defined to quantify the impact of vertically‐varied plant frontal area. Laboratory experiments confirmed that the plant morphology coefficient improved the prediction of near‐bed velocity, near‐bed turbulent kinetic energy and bedload transport rate in canopies with realistic morphology. Plant morphology can alter transport rates by up to an order of magnitude, relative to the assumption of uniform morphology. Plain Language Summary: Aquatic vegetation is a crucial component of river, marsh and delta ecosystems. It has a significant impact on landscape evolution by altering sediment transport. Each vegetation species has a unique shape, but the impact of plant shape on sediment transport has not been previously investigated. This study explained how plant shape impacts sediment transport. Results show that differences in plant shape can change velocity and turbulence close to the channel bed, and thus alter sediment transport rate by an order of magnitude. Plants with greater vertical variation in shape, and specifically less plant volume near the channel bed, produced greater sediment transport. A parameter was defined to quantify the impact of plant shape on flow and sediment transport. By incorporating this parameter, our new model improves the prediction of sediment transport in vegetated regions. This study provides a method for describing the impact of plant shape on flow and sediment transport, which is important to the management and restoration of rivers, marshes and deltas. Key Points: Plant morphology influences the near‐bed velocity, turbulent kinetic energy (TKE) and bedload transport rate inside emergent canopiesA new model accounts for plant morphology in the prediction of near‐bed velocity and TKE and bedload transportFor each canopy solid volume fraction, plants with greater vertical variation in frontal area produce greater bedload transport [ABSTRACT FROM AUTHOR]

With the progress of the times and the leap of science and technology, the application of brick materials and the research on the brick skin in modern architectural design have shown a dual-track development trend of returning to tradition and innovation. Based on the core collection database resources of Web of Science and the CiteSpace visual analysis tool, this paper constructed and analyzed the spatiotemporal map of keyword co-occurrence network, cluster structure, mutation phenomenon, time course and regional distribution map of building brick skin research. The study revealed that in recent years, the research on brick materials has spanned the study of single material properties and extensively involved in the broad world of construction, especially in the integration of green energy-saving technology, the innovation of fine construction technology of brick skin, and the frontier exploration of digital technology in brick masonry, which has shown particularly significant research vitality and development potential. [ABSTRACT FROM AUTHOR]

The bed degradation of a compound channel induced by a base level fall can significantly impact the flood conveyance capability and stability of riverine structures. This study found that severe compound channel degradation is due to the coupled effects of flood discharge and base level fall. Laboratory experiments examined the impact of base level fall on the grain size distribution at the bed surface, flow discharge in the main channel and floodplains, and longitudinal profile of the bed elevation. Two riverbed degradation patterns of a compound channel after base level fall were clarified. Relative to the original bed slope, degradation pattern (I) had a higher bed slope, but degradation pattern (II) had a lower one. A calculation method was proposed to determine the critical conditions for identifying these two riverbed degradation types. Both experimental and published data confirmed that the proposed method is valid for identifying these two compound channel degradation patterns. [ABSTRACT FROM AUTHOR]

This study aims to develop a robust sediment transport model focusing on the vertical two-dimensional water–sediment two-phase flow in which sediments are constantly interacting, hitting each other, gradually becoming smoother and smaller, and accumulating when velocities decrease. The grid-based models currently available can be cumbersome when dealing with phenomena that require replication of this water–sediment interface. Therefore, a two-dimensional water–sediment two-phase flow model based on Smoothed Particle Hydrodynamics (SPH) is established in the macroscopic scale to simulate a large amount of sediment accumulation and propagation typical of a landslide caused by a dam break. In this study, water and sediments are treated as two kinds of fluids with different densities and viscosities to accurately simulate the flow structure, the sediment transport, and the water–sediment interaction process. The interaction model developed treats the interface of the two phases within a unified framework. The model developed was then tested against three applications, and the results obtained confirmed its accuracy in correctly replicating the movement of the sediment phase. The preliminary results obtained can be helpful in providing further insights into the mixing of water and sediments and their propagation following a dam break and the consequent wave profile generated. [ABSTRACT FROM AUTHOR]