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Incipient sediment motion in vegetated open-channel flows predicted by critical flow velocity

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Journal of Hydrodynamics 2022年第1期34卷 63-68页

作者： Xiang Wang Shuolin Li zhong-hua yang Wen-xin huai State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan430072China Department of Civil and Environmental Engineering Duke UniversityDurhamNCUSA Nicholas School of the Environment and Earth Science Duke UniversityDurhamNCUSA

Incipient sediment motion plays a key role in scouring and bed load transport. However, the incipient sediment motion in the vegetated open-channel flows has yet to be fully understood. This study aims to quantify the critical conditions of the sediment particle movement in the presence of emergent and submerged vegetation. A new formula of the critical flow velocity was proposed to predict the incipient sediment motion based on the force balance equation of a sediment particle and the assumption that the velocity distribution in the bed roughness boundary layer fits the logarithmic law. Analysis of the derived formula revealed that the critical flow velocity for incipient sediment motion decreases with the increase in vegetation density. The proposed formula agrees well with the experimental data in the literature, thereby implying that the critical flow velocity can effectively quantify the incipient sediment motion in the vegetated open channel flows.

关键词： Incipient sediment motion critical flow velocity vegetation

Investigation of the sediment transport capacity in vegetated open channel flow

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Journal of Hydrodynamics 2021年第2期33卷 386-389页

作者： Wen-xin huai Xiang Wang Yakun Guo Zhao-hua Sun zhong-hua yang State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan 430072China Faculty of Engineering and Informatics University of BradfordBradfordUK

The suspended sediment transport capacity is important for estimating the suspended load concentration and the ecological environment of the *** far,few studies have been conducted to investigate the suspended sediment transport capacity in the vegetated sediment-laden *** this study,a new formula is derived to predict the sediment transport capacity in a vegetated flow by considering the absolute value of the energy loss between the sediment-laden flow and the clear water ***,the formula is expressed in a practical form by using the logarithmic matching method.

关键词： Sediment transport vegetation suspended sediment concentration

Study of total variation diminishing (TVD) slope limiters in dam-break flow simulation

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Water Science and Engineering 2018年第1期11卷 68-74页

作者： Feng-peng Bai zhong-hua yang Wu-gang Zhou State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University

A two-dimensional （2D） dam-break flow numerical model was developed based on the finite-volume total variation diminishing （TVD） and monotone upstream-centered scheme for conservation laws （MUSCL）-Hancock scheme, which has second-order accuracy in both time and space. A Harten-Lax-van Leer-contact （HLLC） approximate Riemann solver was used to evaluate fluxes. The TVD MUSCL-Hancock numerical scheme utilizes slope limiters, such as the minmod, double minmod, superbee, van Albada, and van Leer limiters, to prevent spurious oscillations and maintain monotonicity near discontinuities. A comparative study of the impact of various slope limiters on the accuracy of the numerical flow model was conducted with several dam-break examples including wet and dry bed cases. The numerical results of the superbee and double minmod limiters agree better with the theoretical solution and have higher accuracy than other limiters in one-dimensional （1D） space. The ratio of the downstream water depth to the upstream water depth was used to select the proper slope limiter. For the 2D numerical model, the superbee limiter should not be used, owing to significant numerical dispersion.

关键词： Dam-break flow TVD MUSCL-Hancock scheme Slope limiter Numerical accuracy Spurious oscillation

Flow dynamics and sediment transport in vegetated rivers:A review

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Journal of Hydrodynamics 2021年第3期33卷 400-420页

作者： Wen-xin huai Shuolin Li Gabriel G.Katul Meng-yang Liu zhong-hua yang State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan430072China Department of Civil and Environmental Engineering Duke UniversityDurhamNCUSA Nicholas School of the Environment and Earth Science Duke UniversityDurhamNCUSA

The significance of riparian vegetation on river flow and material transport is not in *** laws,sediment erosion and deposition,and element cycling must all be adjusted from their canonical rough-wall boundary layer to accommodate the presence of aquatic *** turn,the growth and colonization of riparian vegetation are affected by fluvial processes and river morphology on longer time *** interactions and feedbacks at multiple time scales are now drawing significant attention within the research community given their relevance to river *** this reason,a review summarizing methods,general laws,qualitative cognition,and quantitative models regarding the interplay between aquatic plants,flow dynamics,and sediment transport in vegetated rivers is in ***,pitfalls,knowledge gaps,and daunting challenges to the current state of knowledge are also *** a multidisciplinary research topic,a future research agenda and opportunities pertinent to river management and enhancement of ecosystem services are also highlighted.

关键词： Canopy flow river morphology riparian vegetation sediment transport

Lattice Boltzmann method for simulating flows in open-channel with partial emergent rigid vegetation cover

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Journal of Hydrodynamics 2019年第4期31卷 717-724页

作者： zhong-hua yang Feng-peng Bai Wen-xin huai Cheng-guang Li State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University Wuhan 430072 China Changjiang Water Resources Protection Institute Wuhan 430051 China Shandong Provincial Key Laboratory of Water Resources and Water Environment Water Resources Research Institute of Shandong Province Jinan 250013 China

Flows in open-channel with partial emergent rigid vegetation cover are simulated using the lattice Boltzmann method (LBM) described by the 2-D nonlinear shallow water equations. The effect of vegetation is represented with the vegetation roughness coefficient, which is related to the vegetation density, diameter of the vegetation elements and drag coefficient. The model is verified by three numerical tests: flow in a 180° curved open channel with partial vegetation cover at the outer bank, flow in a rectangular channel with a finite patch of vegetation and flow in a rectangular channel with a vegetated bank. Numerical results are compared with the experimental data, and the good agreement proved that the presented model can model the vegetated channel flows correctly.

关键词： Open-channel flow rigid vegetation lattice Boltzmann method (LBM) shallow water equations vegetation roughness coefficient

The ultrasonic harmonic scalpel for circumcision： experimental evaluation using dogs

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Asian Journal of Andrology 2013年第1期15卷 93-96页

作者： Mou Peng Zhe Meng zhong-hua yang Xing-huan Wang Department of Urology Zhongnan Hospital of Wuhan University Wuhan 430071 China

Male circumcision is one of the most commonly performed operations worldwide, and many novel techniques have been developed for better postoperative outcomes. The purpose of this study was to explore the feasibility of applying the ultracision harmonic scalpel （UHS） for circumcision by using dogs. Sixteen adult male dogs were divided into two groups： the UHS group and the control group. The dogs were circumcised with either the UHS or a conventional scalpel. The UHS circumcision procedure and the effects were imaged 1 week after surgery. The two groups were compared with respect to the operative time and volume of blood loss. Postoperative complications, including oedema, infection, bleeding of the incision and wound dehiscence, were recorded for both groups. The mean operative time for the UHS group was only 5.1 min compared with the 35.5 min of the conventional group. The mean blood loss was less than 2 ml for the UHS group and 15 ml for the conventional group. There was only one case of mild oedema in the UHS group, but the postoperative complications in the conventional group included two cases of mild oedema, one infection of the incision and one Case of bleeding of the incision. In conclusion, circumcision using UHS is a novel technique to treat patients with phimosis and excessive foreskin, and this method has a short operative time, less blood loss and fewer complications than the conventional scalpel method. This small animal study orovides a basis for embarking on a larger-scale clinical trial of the UHS.

关键词： conventional circumcision dog electrocautery technique Plastibell device ultracision harmonic scalpel

Effect of vacuum on porosity and mechanical properties of high-pressure die-cast pure copper

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China Foundry 2019年第4期16卷 232-237页

作者： Hong-mei yang Zhi-peng Guo hua-zhong yang Zhi-hua Fu Zhou-meng Pu Shou-mei Xiong School of Materials Science and Engineering Tsinghua University Beijing 100084 China Key Laboratory for Advanced Materials Processing Technology Ministry of Education Beijing 100084 China Yunnan Copper Die-casting Technology Co. Ltd. Kunming 650001 China

Pure copper tensile bars were produced by conventional die casting(HPDC) and vacuum-assist die casting(VADC) processes. Porosity and mechanical properties were investigated by using optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), X-ray computed tomography(XCT) and tensile tester. Results show that porosities including gas porosity and shrinkage porosity could be observed in copper castings. Since the application of vacuum could reduce filling related gas entrapment and facilitate solidification due to the increased heat transfer between metal and die, both number and size of the entrapped gases, as well as shrinkage porosities were significantly reduced in vacuum-assist die castings of pure copper. The porosity fraction decreased from 2.243% to 0.875% compared with that of the conventional die casting. Besides, mechanical properties were improved significantly, i.e., by 15% for ultimate tensile strength and three times for elongation.

关键词： vacuum copper high pressure die casting (HPDC) mechanical properties porosity

Design and Synthesis of Novel Fluorine-containing Acrylates

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Chinese Chemical Letters 2005年第10期16卷 1293-1296页

作者： Yan Chao WU Chao WU Xiao Mao ZOU Fang zhong HU hua Zheng yang State Key Laboratory of Element-Organic Chemistry Institute of Element-Organic Chemistry Nankai University Tianjin 300071

A series of novel fluorine-containing acrylates 6a-6g were synthesized via the condensation of ethyl cyanoacetate and trifluoroacetic anhydride, followed by chloridization and the coupling reaction with amines. These new compounds exhibited some biological activity as preliminary bioassay indicated. A plausible reaction mechanism was outlined and discussed.

关键词： Fluorine-containing compound acrylates synthesis.

A novel rat model of seminal vesiculitis

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Asian Journal of Andrology 2019年第4期21卷 360-364页

作者： Peng Zhang Xiao-Long Wang zhong-hua yang Xin-Jun Su Xing-huan Wang Department of Urology Zhongnan Hospital Wuhan University Wuhan 430071 China Department of Urology Research Lab/LIFE-Zentrum University of Munich (LMU) Munchen 81377 Germany

We aimed to establish a novel rat model of seminal vesiculitis that would provide an effective approach to investigate the pathogenesis of this disease in the future. Eight male rats received the same operation, during which the root of one of the two seminal vesicles was partly ligatured with sutures and the other vesicle was left in tact. The samples of seminal vesicles were harvested on the 8th day followi ng the operation. Hematoxylin and eosi n and Mass on's trichrome stains were used to observe the histopathology and the presenee of fibrous tissue in seminal vesicles, respectively. Immunoblotting and immunohistochemistry were applied to determine the tumor n ecrosis factor-alpha and cyclooxygenase-2 levels in semi nal vesicle tissues. Real-time fluoresce nee qua ntitative polymerase chain reaction was performed to measure the gene expression levels of proinflammatory cytokines. H2O2 levels in the seminal plasma from the seminal vesicle were also measured. Hematoxylin and eosin staining suggested that there was inflammatory cell in filtration into the semi nal vesicles treated by partial root ligati on. The tumor n ecrosis factor-alpha and cyclooxygenase-2 proteins were significantly upregulated in the treated seminal vesicles. The tumor necrosis factor-alpha, cyclooxygenase, interleukin 6, and inducible nitric oxide synthase mRNA expression levels were also upregulated in the treated seminal vesicles. The H2O2 levels in the seminal plasma from seminal vesicles with partial root ligation were significantly elevated compared with those from vesicle left intact. In conclusion, partially ligating the root of the seminal vesicle via sutures in rats is an effective method to establish a seminal vesiculitis rat model.

关键词： cyclooxygenase-2 rat model seminal vesiculitis tumor necrosis factor