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High-resolution tsunami hazard assessment for the Guangdong-Hong Kong-Macao Greater Bay Area based on a non-hydrostatic tsunami model

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Science China Earth Sciences 2024年第7期67卷 2326-2351页

作者： Yifan ZHU Chao AN Houyun YU Wei ZHANG Xiaofei CHEN Key Laboratory of hydrodynamics(Ministry of Education) School of Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China department of Earth and Space Sciences Southern University of Science and Technology Shenzhen 518055China

The Guangdong-Hong Kong-Macao Greater Bay Area(GBA)is threatened by potential tsunami hazards from the Littoral Fault Zone(LFZ)and the Manila subduction zone(MSZ),and may suffer huge damage because of its dense population,concentrated infrastructure,and low-lying coasts.Previous tsunami studies for the GBA made simple assumptions on the mechanisms of LFZ earthquakes,and used coarse bathymetry data in tsunami simulation,which limited the prediction of detailed tsunami hazard characteristics.In this paper,we develop a parallel dispersive tsunami model PCOMCOT to efficiently simulate dispersive,nonlinear,and breaking tsunami waves.We also construct large-scale and high-resolution bathymetry models for the GBA by correcting and integrating various data sources.Dynamic rupture simulation is performed for the LFZ to obtain a more reliable earthquake source model.We propose several representative earthquake scenarios for the LFZ and MSZ,and use PCOMCOT to calculate the resulting tsunami waves,currents,and inundation in the GBA.Our results indicate that if an M_(w)7.5 oblique-slip earthquake occurs in the LFZ off the Pearl River Estuary(PRE),the subsequent tsunami will primarily impact Hong Kong,causing maximum positive and negative waves of around 1 m and -2 m,respectively,along with slightly destructive currents(≥1.5 m/s).An M_(w)9.0 MSZ megathrust earthquake can lead to widespread inundation with>1 m depth on the outlying islands of Macao and in the urban areas of Hong Kong around the Victoria Harbour.Besides,it will also cause catastrophic tsunami currents along the narrow waterways in Hong Kong and Macao,and the spatial distribution of strong currents(≥3 m/s)shows a considerable discrepancy from the areas of serious inundation.Thus,more attention should be paid to the potential impacts of tsunami currents on the GBA.

关键词： Tsunami hazards Inundation Tsunami currents Non-hydrostatic model Guangdong-Hong Kong-Macao Greater Bay Area

AN EXPERIMENTAL STUDY ON THREE DIMENSIONAL STRUCTURE OF BAROCLINIC WAVY JET STREAM IN A ROTATING ANNULUS SUBJECT TO RADIAL TEMPERATURE GRADIENT

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Journal of hydrodynamics 2000年第4期12卷 26-35页

作者： Su Xiao bin, Wei Gang hydrodynamics department of Meteorology College, P. L. A. University of Science and Engineering. Nanjing, 211101, P.R.China (Received Dec.1, 1999) hydrodynamics Dep. Meteorology Coll. PLA Univ. of Sci. and Eng. Nanjing 211101 China

Three dimensional structure of baroclinic wavy jet was experimentally studied in rotating annulus subject to a negative radial temperature gradient. General features of wavy surface jet in the system were obtained. Based on the precise measurements of velocity distribution of the jet with LDV and the three dimensional temperature field in the convective system, three dimensional thermodynamic structures of jet were gained, and by using a correlation of three dimensional disturbed temperature, the unstable mechanism of disturbed temperature of baroclinic fluid in a rotating system was further discussed.

关键词： baroclinic wave rotating fluid jet correlation coefficien8

Bionic soft robotic gripper with feedback control for adaptive grasping and capturing applications

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Frontiers of Mechanical Engineering 2024年第1期19卷 129-148页

作者： Tingke WU Zhuyong LIU Ziqi MA Boyang WANG Daolin MA Hexi YU department of Engineering Mechanics School of Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200240China MOE Key Laboratory of hydrodynamics Shanghai Jiao Tong UniversityShanghai 200240China

Robots are playing an increasingly important role in engineering applications.Soft robots have promising applications in several fields due to their inherent advantages of compliance,low density,and soft interactions.A soft gripper based on bio-inspiration is proposed in this study.We analyze the cushioning and energy absorption mechanism of human fingertips in detail and provide insights for designing a soft gripper with a variable stiffness structure.We investigate the grasping modes through a large deformation modeling approach,which is verified through experiments.The characteristics of the three grasping modes are quantified through testing and can provide guidance for robotics manipulation.First,the adaptability of the soft gripper is verified by grasping multi-scale and extremely soft objects.Second,a cushioning model of the soft gripper is proposed,and the effectiveness of cushioning is verified by grasping extremely sharp objects and living organisms.Notably,we validate the advantages of the variable stiffness of the soft gripper,and the results show that the soft robot can robustly complete assemblies with a gap of only 0.1 mm.Owing to the unstructured nature of the engineering environment,the soft gripper can be applied in complex environments based on the abovementioned experimental analysis.Finally,we design the soft robotics system with feedback capture based on the inspiration of human catching behavior.The feasibility of engineering applications is initially verified through fast capture experiments on moving objects.The design concept of this robot can provide new insights for bionic machinery.

关键词： soft bionic gripper variable stiffness structure large deformation modeling feedback control soft robotic system

Experimental observation on water entry of a sphere in regular wave

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Theoretical & Applied Mechanics Letters 2023年第5期13卷 367-374页

作者： Qian Wang Changze Zhao Haocheng Lu Hua Liu department of Engineering Mechanics MOE Key Laboratory of HydrodynamicsShanghai Jiao Tong UniversityShanghai 200240China

This paper presents a novel experiment to observe the whole water entry process of a free-falling sphere into a regular wave.A time-accurate synchronizing system modulates the moment elaborately to ensure the sphere impacting onto the water surface at the desirable wave phase.Four high-speed cameras focus locally to measure the high-precision size of the cavity evolution.Meanwhile,the aggregated field view of the camera array covers both the splash above the free surface and the entire cavity in the wave.The detailed methodologies are described and verified for the hardware set-up and the image post-processing.The theoretical maximum deviation is 1.7%on the space scale.The integral morphology of the cavity is captured precisely in the coordinate system during the sphere penetrates through the water at four representative wave phases and the still water.The result shows that the horizontal velocity of the fluid particle in the wave impels the cavity and changes the shape distinctly.Notably,the wave motion causes the cavity to pinch offearlier at the wave trough phase and later at the wave crest phase than in the still water.The wave motion influences the falling process of the sphere slightly in the present parameters.

关键词： Physical experiment Water entry Free-falling sphere Regular wave

Uniform decomposition of velocity gradient tensor

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Journal of hydrodynamics 2024年第1期36卷 24-34页

作者： Chenxi Ma Chaoqun Liu department of Mathematics University of Texas at ArlingtonArlingtonTXUSA

In this paper,the principal decomposition of the velocity gradient tensor[∇v]is discussed in 3 cases based on the discriminant∆:∆0 with 3 distinct real eigen values,and∆=0 with 1 or 2 distinct real eigen values.The velocity gradient tensor can also be classified as rotation point,which can be decomposed into three parts,i.e.,rotation[R],shear[S]and stretching/compression[SC],and non-rotation point,we defined a new resistance term[L],and the tensor can be decomposed into three parts,i.e.,resistance[L],shear[S]and stretching/compression[SC].Example matric are also displayed to demonstrate the new decomposition.Connections of principal decomposition between 3 different cases,and between Resistance and Liutex will also be discussed.

关键词： Velocity gradient Liutex resistance fluid kinematics

Flow Regimes in Bubble Columns with and without Internals: A Review

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Fluid Dynamics & Materials Processing 2024年第2期20卷 239-256页

作者： Ayat N.Mahmood Amer A.Abdulrahman Laith S.Sabri Abbas J.Sultan Hasan Shakir Majdi Muthanna H.Al-Dahhan department of Chemical Engineering University of Technology-IraqBaghdadIraq Chemical and Petroleum Industries Engineering department Al-Mustaqbal University CollegeBabylonIraq department of Chemical and Biochemical Engineering Missouri University of Science and TechnologyRollaUSA

hydrodynamics characterization in terms ofﬂow regime behavior is a crucial task to enhance the design of bubble column reactors and scaling up related methodologies.This review presents recent studies on the typicalﬂow regimes established in bubble columns.Some effort is also provided to introduce relevant deﬁnitions pertaining to thisﬁeld,namely,that of“void fraction”and related(local,chordal,cross-sectional and volumetric)variants.Experimental studies involving different parameters that affect design and operating conditions are also discussed in detail.In the second part of the review,the attention is shifted to cases with internals of various types(perfo-rated plates,bafﬂes,vibrating helical springs,mixers,and heat exchanger tubes)immersed in the bubble columns.It is shown that the presence of these elements has a limited inﬂuence on the global column hydrodynamics.However,they can make the homogeneousﬂow regime more stable in terms of transition gas velocity and transi-tion holdup value.The last section is used to highlight gaps which have not beenﬁlled yet and future directions of investigation.

关键词： hydrodynamics ﬂow regime bubble column heat-exchanging internals

Interaction Mechanisms between Natural Debris Flow and Rigid Barrier Deflectors:A New Perspective for Rational Design and Optimal Arrangement

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 1679-1699页

作者： Yu Huang Beilei Liu Dianlei Feng Hao Shi department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai200092China department of Hydraulic Engineering College of Civil EngineeringTongji UniversityShanghai200092China

Rigid barrier deflectors can effectively prevent overspilling landslides,and can satisfy disaster prevention requirements.However,the mechanisms of interaction between natural granular flow and rigid barrier deflectors require further investigation.To date,few studies have investigated the impact of deflectors on controlling viscous debris flows for geological disaster prevention.To investigate the effect of rigid barrier deflectors on impact mechanisms,a numerical model using the smoothed particle hydrodynamics(SPH)method with the Herschel–Bulkley model is proposed to simulate the interaction between natural viscous flow and single/dual barriers with and without deflectors.This model was validated using laboratory flume test data from the literature.Then,the model was used to investigate the influence of the deflector angle and multi-barrier arrangements.The optimal configuration of multi-barriers was analyzed with consideration to the barrier height and distance between the barriers,because these metrics have a significant impact on the viscous flow pile-up,run-up,and overflow mechanisms.The investigation considered the energy dissipation process,retention efficiency,and dead-zone formation.Compared with bare barriers with similar geometric characteristics and spatial distribution,rigid barriers with deflectors exhibit superior effectiveness in preventing the overflow and overspilling of viscous debris flow.Recommendations for the rational design of deflectors and the optimal arrangement of multi-barriers are provided to mitigate geological disasters.

关键词： Rigid barrier deflectors deflector angle single-barrier dual-barrier arrangements viscous debris flow over-spilling delta-plus-SPH

Numerical study of the near-wall vortical structures in particle-laden turbulent flow by a new vortex identification method-Liutex

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Journal of hydrodynamics 2024年第1期36卷 53-60页

作者： Farid Rousta Goodarz Ahmadi Bamdad Lessani Chaoqun Liu department of Mechanical and Aerospace Engineering Clarkson UniversityPotsdamNYUSA Mechanical Engineering and Engineering Science The University of North Carolina at CharlotteNCUSA department of Mathematics University of Texas at ArlingtonArlingtonTXUSA

This study investigates turbulent particle-laden channel flows using direct numerical simulations employing the Eulerian-Lagrangian method.A two-way coupling approach is adopted to explore the mutual interaction between particles and fluid flow.The considered cases include flow with particle Stokes number varying from St=2 up to St=100 while maintaining a constant Reynolds number of Reτ=180 across all cases.A novel vortex identification method,Liutex(Rortex),is employed to assess its efficacy in capturing near-wall turbulent coherent structures and their interactions with particles.The Liutex method provides valuable information on vortex strength and vectors at each location,enabling a detailed examination of the complex interaction between fluid and particulate phases.As widely acknowledged,the interplay between clockwise and counterclockwise vortices in the near-wall region gives rise to low-speed streaks along the wall.These low-speed streaks serve as preferential zones for particle concentration,depending upon the particle Stokes number.It is shown that the Liutex method can capture these vortices and identify the location of low-speed streaks.Additionally,it is observed that the particle Stokes number(size)significantly affects both the strength of these vortices and the streaky structure exhibited by particles.Furthermore,a quantitative analysis of particle behavior in the near-wall region and the formation of elongated particle lines was carried out.This involved examining the average fluid streamwise velocity fluctuations at particle locations,average particle concentration,and the normal velocity of particles for each set of particle Stokes numbers.The investigation reveals the intricate interplay between particles and near-wall structures and the significant influence of particles Stokes number.This study contributes to a deeper understanding of turbulent particle-laden channel flow dynamics.

关键词： Turbulent channel flow particle-laden flow direct numerical simulation(DNS) Eulerian-Lagrangian vortex identification turbulence coherent structures Liutex

Error evaluation of binocular vision method for reconstructing breaking wave surface

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Journal of hydrodynamics 2022年第5期34卷 970-974页

作者： Qian Wang Hao-cheng Lu Chang-ze Zhao Hua Liu department of Engineering Mechanics Shanghai Jiao Tong UniversityShanghai200240China Key Laboratory of hydrodynamics(MOE) Shanghai Jiao Tong UniversityShanghai200240China

Quantization error and its source of the binocular stereo vision technique are evaluated by measuring breaking wave surface in wave flume.The verification test focuses on the run-up process of a breaking solitary wave on a slope.The three-dimensional topography of the free surface is reconstructed at three representative stages of wave propagation.The two-dimensional profile from the side view and statistical data are used to evaluate the quantization error.The breaking degree of wave surface has a mild influence on the performance of stereo reconstruction in the current configuration.The mean error of detecting the surface elevation is about 2 mm,around 0.1%of the measurement distance.Sixty percent of the error comes from the deficient match in image interrogation,and the remaining forty percent arises from the limited system configuration.The precise stereo measurement of the breaking surface shows that the present binocular vision system provides a new technique in experiments in hydrodynamics with the breaking surface.

关键词： Binocular stereo reconstruction surface deformation breaking wave image processing