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MPM simulations of dam-break floods

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Journal of Hydrodynamics 2017年第3期29卷 397-404页

作者： Xuanyu Zhao dongfang liang Mario Martinelli Department of Engineering University of CambridgeCambridgeUK Deltares DelftThe Netherlands

Owing to its ability of modelling large deformations and the ease of dealing with moving boundary conditions,the material point method is gaining popularity in geotechnical engineering *** this paper,this promising Lagrangian method is applied to hydrodynamic problems to further explore its *** collapse of water columns with different initial aspect ratios is simulated by the material point *** order to test the accuracy and stability of the material point method,simulations are first validated using experimental data and results of mature numerical ***,the model is used to ascertain the critical aspect ratio for the widely-used shallow water equations to give satisfactory *** the comparisons between the simulations based on the material point method and the shallow water equations,the critical aspect ratio for the suitable use of the shallow water equations is found to be 1.

关键词： Material point method dam-break floods Lagrangian method shallow water equations

Study on the critical submergence of surface vortices and the design of anti-vortex intakes

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Science China(Technological Sciences) 2011年第4期54卷 799-804页

作者： WANG YingKui JIANG ChunBo liang dongfang State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing 100084China Department of Engineering University of CambridgeCambridgeCB2 1PZUK

Surface vortex behavior in front of the tunnel intake was investigated in this *** critical submergence of vortex was discussed based on the concept of 'critical spherical sink surface'(CSSS).The vortex formation and evolution at the tunnel intake were analyzed based on the theory of CSSS considering the effect of circulation.A theory was proposed to explain the surface *** theoretical development was verified by the physical model experiments of Xiluodu hydropower *** radial velocity and vortex circulation were considered as the main factors that influence the formation and evolution of surface ***,an anti-vortex intake configuration was proposed to weaken the air-core vortex in front of the tunnel intakes of the hydraulic structures.

关键词： critical submergence critical spherical sink surface surface vortex tunnel intake physical model experiment

Detached-eddy simulation of turbulent coherent structures around groynes in a trapezoidal open channel

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Journal of Hydrodynamics 2020年第2期32卷 326-336页

作者： Jing-xin Zhang Jian Wang Xiang Fan dongfang liang Key Laboratory of Hydrodynamics(Ministry of Education) shanghai Jiao Tong UniversityShanghai200240China School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China

The hydrodynamics in a straight open channel with a multiple-embayment groyne field was investigated using the detached-eddy simulation(DES).A series of short groynes were included on a 1:3 side slope of the *** work focuses on the turbulent coherent structures around groynes on an uneven *** around groyne fields are characterized by massive separation and highly unsteady *** can capture a wide spectrum of eddies at a lower computational cost than the large eddy simulation(LES)or direct numerical simulation(DNS).In the present work,a zonal DES model(ZDES)was used to simulate the flow around *** ZDES model is a modified version of the DES designed to overcome the model-stress depletion(MSD)of the RANS/LES hybrid *** vortex system consists of the horseshoe vortex(HV)formed at the base of the obstructions,the necklace vortex(NV)that wrapped the groyne tips near the free surface,and the shedding vortex(SV)underneath the free *** effects of the incident flow and local topography on the vortex evolution were investigated by analyzing the mean flow structures and the instantaneous turbulent flow *** important vortices cannot be captured because of the averaging process,while some flow structures cannot be observed in the instantaneous *** mean flow is only a reflection of the averaging process when complex vortices are present.

关键词： Open channel flow groyne free surface detached eddy simulation turbulent coherent structure

Modelling large deformation and soil–water–structure interaction with material point method:Briefing on MPM2017 conference

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Journal of Hydrodynamics 2017年第3期29卷 393-396页

作者： Alexander Rohe dongfang liang Deltares DelftThe Netherlands Department of Engineering University of CambridgeCambridgeUK

The 1st International Conference on the Material Point Method for ＂Modelling Large Deformation and Soil–Water–Structure Interaction＂（MPM2017）was held in Delft,The Netherlands on 10-13 January *** is the first conference organised by the Anura3D MPM Research Community,following a series of international workshops and symposia previously held in The Netherlands,UK,Spain and Italy,as part of the European Commission FP7 Marie-Curie project *** are delighted to present seven contributions in this Special Column of the Journal of Hydrodynamics,and take this opportunity to announce that the 2nd conference,MPM2019,will be held in Cambridge,UK in January 2019.

关键词： Material point method soil–water–structure interaction meshfree methods particle methods

Numerical investigation of shallow wake behind a patch of rigid emergent vegetation

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Journal of Hydrodynamics 2021年第4期33卷 673-687页

作者： Jian Wang Jing-xin Zhang dongfang liang Lian Gan School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China Key Laboratory of Hydrodynamics(Ministry of Education) Shanghai Jiao Tong UniversityShanghai200240China Department of Engineering University of CambridgeCambridgeUK Department of Engineering Durham UniversityDurhamUK

The shallow water flow through and around a patch of rigid emergent vegetation was investigated numerically. The mean flow field and turbulent structures were studied, especially their dependence on the solid volume fraction (SVF) of the patch and the bed friction. Two streamwise velocity scales, U1s at the starting point of the steady wake and U1e at the downstream end of the steady wake, and the length of the steady wake L1 were used to describe the steady wake behind the patch. U1s was found to be related to SVF only. However, U1e and L1 were influenced by both the SVF and the wake stability parameter S. For a sparse patch, U1e was equal to U1s, and L1 decreased with the increase of S. For a mid-dense patch, U1e was always smaller than U1s, and it increased with S and gradually approached U1s. The increase of U1e reduced the lateral velocity difference between the flows inside and outside the wake, which resulted in the increase of L1. For a highly dense patch, U1e and L1 did not increase unless S was larger than a critical value. A new parameter, r, was proposed to represent the development rate of the steady wake. The numerical results showed that r increased monotonously with S for mid-dense patches.

关键词： Shallow water vegetated flow wake bed friction

Incompressible SPH simulation of solitary wave propagation on permeable beaches

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Journal of Hydrodynamics 2020年第4期32卷 664-671页

作者： Chiaki Tsurudome dongfang liang Yuma Shimizu Abbas Khayyer Hitoshi Gotoh Department of Engineering University of CambridgeTrumpington StreetCambridgeUK Graduate School of Engineering Kyoto UniversityKyotoJapan

Wave propagation on uniformly sloped beaches is a canonical coastal engineering topic that has been studied extensively in the past few ***,most of these studies treat beaches as solid boundaries even though they are often made of porous materials,such as sediment and *** beaches struck by tsunami-like waves have not been adequately *** is expected that the degree of penneability plays a crucial role in mitigating the impact of the *** study examines solitary wave run-ups on sandy beaches using an incompressible smoothed particle hydrodynamics(ISPH)*** permeability of the beach is considered to be directly related to the diameter of its constituent sand *** obtain a satisfactory pressure field,which cannot be achieved using the original ISPH algorithm,the source term of the pressure Poisson equation has been modified based on a higher-order source-term *** within the porous medium are computed in the same framework as those outside the porous *** the current model,no transition zone is needed at the boundary of the porous *** wave-attenuation effect of the porous medium is discussed,with a particular focus on the relationship between the mn-up height and grainsize.

关键词： Solitary wave porosity incompressible smoothed particle hydrodynamics(ISPH) run-up

Experimental study of water and dissolved pollutant runoffs on impervious surfaces

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Journal of Hydrodynamics 2016年第1期28卷 162-165页

作者：肖洋张涛涛 dongfang liang Jack M.CHEN State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University College of Water Conservancy and Hydropower Engineering Hohai University Department of Engineering University of Cambridge

The water and dissolved pollutant runoffs on impervious surfaces are the essential factor to be considered in design methods to minimize the impacts of the diffuse water pollution. In this paper, experiments are conducted to study the water and dissolved pollutant runoffs on impervious surfaces for different rainfall intensities and surface roughnesses. It is shown that a larger rainfall intensity and a smaller surface roughness reduce the time of concentration and increase the pollutant transport rate. Most of the pollutant runoffs take place at the initial stage of the rainfall. The pollutant transport rate rapidly reaches a peak and then gradually drops to zero.

关键词： rainfall-runoff diffuse pollution overland flow flooding urban runoff

Achieving consistency of flexible surface acoustic wave sensors with artificial intelligence

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Microsystems & Nanoengineering 2024年第4期10卷 249-260页

作者： Zhangbin Ji Jian Zhou Yihao Guo Yanhong Xia Ahmed Abkar dongfang liang Yongqing Fu College of Mechanical and Vehicle Engineering Hunan UniversityChangsha 410082China Department of Engineering University of CambridgeTrumpington StreetCambridge CB21PZUK Faculty of Engineering and Environment Northumbria UniversityNewcastle upon Tyne NE18STUK

Flexible surface acoustic wave technology has garnered significant attention for wearable electronics and sensing ***,the mechanical strains induced by random deformation of these flexible SAWs during sensing often significantly alter the specific sensing signals,causing critical issues such as inconsistency of the sensing results on a curved/flexible *** address this challenge,we first developed high-performance AlScN piezoelectric filmbased flexible SAW sensors,investigated their response characteristics both theoretically and experimentally under various bending strains and UV illumination conditions,and achieved a high UV sensitivity of 1.71 KHz/(mW/cm^(2)).To ensure reliable and consistent UV detection and eliminate the interference of bending strain on SAW sensors,we proposed using key features within the response signals of a single flexible SAW device to establish a regression model based on machine learning algorithms for precise UV detection under dynamic strain disturbances,successfully decoupling the interference of bending strain from target UV *** results indicate that under strain interferences from 0 to 1160μεthe model based on the extreme gradient boosting algorithm exhibits optimal UV prediction *** a demonstration for practical applications,flexible SAW sensors were adhered to four different locations on spacecraft model surfaces,including flat and three curved surfaces with radii of curvature of 14.5,11.5,and 5.8 *** flexible SAW sensors demonstrated high reliability and consistency in terms of UV sensing performance under random bending conditions,with results consistent with those on a flat surface.

关键词： artificial boosting consistency

Experimental investigation on scour topography around high-rise structure foundations

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International Journal of Sediment Research 2021年第3期36卷 348-361页

作者： Yang Xiao Hao Jia Dawei Guan dongfang liang Saiyu Yuan Hongwu Tang State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Yangtze Institute for Conservation and Development Hohai University College of Harbour Coastal and Offshore Engineering Hohai University Department of Engineering University of Cambridge

The current study aims to investigate the characteristics of scour topography around High-Rise Structure Foundations(HRSFs) via physical modeling tests. Clear-water scour tests with a uniform non-cohesive bed are modeled under the action of unidirectional steady flows. Time variations of the erosion and deposition topography are measured. The results show that deposition downstream of the first dune behind the HRSF is not located on the centerline of the wake. The deposition pattern indicates that a long steady wake region exists behind the permeable foundation. The scour depth around an HRSF is much less than that around a monopile because of the structural permeability, which gives rise to the bleed flow and a weakened downflow and horseshoe vortex. Additionally, the asymmetry of the HRSF affects the scour rate but not the final equilibrium scour depth. The average scour slope decreases along the direction of the flow. On the contrary, the scour radial distance increases along the direction of the flow,with the average value changing from 1.36 Deto 2.35 De(where Deis the equivalent diameter of the foundation). Furthermore, the scour hole around the HRSF is serrated rather than smooth owing to the presence of multiple piles. Empirical formulae are suggested for estimating the evolution of scour depth and volume. These laboratory experiments provide reference information for relevant numerical modeling studies and can be applied to guide engineering designs in an ocean area.

关键词： High-rise structure foundation Scour Sediment transport Pile groups