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The visualization of turbulent coherent structure in open channel flow

Journal of Hydrodynamics 2019年第2期31卷 266-273页

作者： Xiao-dong Bai Wei Zhang Qing-he Fang Yong Wang Jin-hai Zheng An-xin Guo Ministry of Education Key Laboratory of Coastal Disaster and Defence Hohai UniversityNanjing 210098China College of Harbor Coastal and Offshore EngineeringHohai UniversityNanjing 21009China Science and Technology on Water Jet Propulsion Laboratory Marine Design and Research Institute of ChinaShanghai 200011China Ministry of Education Key Laboratory of Structural Dynamic Behavior and Control School of Civil EngineeringHarbin Institute of TechnologyHarbin 150090China Max Planck Institute for Dynamics and Self-Organization GottingenGermany

Due to its multiscale and multi-layer natures,the coherent structures of turbulent in the open channel flow is complex and difficult to be visualized for understanding its *** this paper,five types of methods for the vortical structure in the fluids,namely the Q-criterion,the vorticity,the Omega method,the velocity-vorticity correlation structures(VVCS)as well as the most recent Rortex method,are adopted to visualize the turbulent flow in the open *** the free surface modelled as a free slip boundary,a direct numerical simulation(DNS)is carried out to study the multi-layered flow structure characteristics under the free *** visualization results by the Q-criterion,the vorticity,the Omega method and the Rortex are firstly *** the turbulent flow layers near the free surface are identified with corresponding anisotropy ***,the VVCS within various turbulence layers are visualized *** research indicates that the VVCS can straightforwardly show the geometry information of the cohere nt structures of turbulent in different layers for the ope n channel flow.

关键词： Open channel flow flow visualization velocity-vorticity coherent structure direct numerical simulation(DNS)

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Impact of residual stress on high and very high cycle fatigue behaviours of Inconel 718 at room temperature and 650 °C

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International Journal of Fatigue 2025年

作者： Yong-Jie Wang Hua-Yan Hu Yi-Fan Yang Nai-Jian Dong Xiang-Fan Nie Jian-Feng Wen Miao Song Yong-Hui Chen Shan-Tung Tu Key Laboratory of Pressure Systems and Safety Ministry of Education School of Mechanical and Power Engineering East China University of Science and Technology Shanghai 200237 China School of Nuclear Science and Engineering Shanghai Jiao Tong University Shanghai 200240 China Science and Technology on Plasma Dynamic Laboratory Air Force Engineering University Xi’an 710038 China Shanghai Institute of Aircraft Mechanics and Control 130 Meilong Road Shanghai 200237 China National Key Laboratory of Strength and Structural Integrity Aircraft Strength Research Institute of China Xi’an 710065 China

High and very high cycle fatigue behaviours are influenced not only by the machined surface quality but also by the inherent stress state of components. In the study, the influence of inherent residual stress state within a forged Inconel 718 turbine disc on high and very high cycle fatigue life was investigated through ultrasonic fatigue testing at 20 °C and 650 °C. At 20 °C, the exterior of the turbine disc exhibited approximately 190 MPa higher fatigue limit compared to the interior, attributed to inherent compressive residual stress partially offsetting the applied stress, thereby reducing the mean stress. However, this discrepancy in fatigue limit between the exterior and interior positions became negligible at 650 °C due to stress relaxation during high temperature. A modified Basquin model incorporating surface quality and inherent residual stress effects on fatigue life was proposed. This modified model accurately predicated fatigue life for specimens with varying inherent residual stress and surface conditions at 20 °C and 650 °C, with fatigue data falling into the range of life factors ±3, compared to the range of life factors ±30 in classical Basquin model.

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Recovering compressed images for automatic crack segmentation using generative models

arXiv

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arXiv 2020年

作者： Huang, Yong Zhang, Haoyu Li, Hui Wu, Stephen Key Laboratory of Intelligent Disaster Prevention and Mitigation for Civil Infrastructures Ministry of Industry and Information Technology Harbin Heilongjiang150090 China Ministry of Education Key Laboratory of Structural Dynamic Behavior and Control School of Civil Engineering Harbin Institute of Technology Harbin China Institute of Statistical Mathematics Research Organization of Information and Systems 10-3 Midori-cho Tachikawa Tokyo190-8562 Japan Graduate University for Advanced Studies SOKENDAI 10-3 Midori-cho Tachikawa Tokyo190-8562 Japan

In a structural health monitoring (SHM) system that uses digital cameras to monitor cracks of structural surfaces, techniques for reliable and effective data compression are essential to ensure a stable and energy-efficient crack images transmission in wireless devices, e.g., drones and robots with high definition cameras installed. Compressive sensing (CS) is a signal processing technique that allows accurate recovery of a signal from a sampling rate much smaller than the limitation of the Nyquist sampling theorem. The conventional CS method is based on the principle that, through a regularized optimization, the sparsity property of the original signals in some domain can be exploited to get the exact reconstruction with a high probability. However, the strong assumption of the signals being highly sparse in an invertible space is relatively hard for real crack images. In this paper, we present a new approach of CS that replaces the sparsity regularization with a generative model that is able to effectively capture a low dimension representation of targeted images. We develop a recovery framework for automatic crack segmentation of compressed crack images based on this new CS method and demonstrate the remarkable performance of the method taking advantage of the strong capability of generative models to capture the necessary features required in the crack segmentation task even the backgrounds of the generated images are not well reconstructed. The superior performance of our recovery framework is illustrated by comparing with three existing CS algorithms. Furthermore, we show that our framework is extensible to other common problems in automatic crack segmentation, such as defect recovery from motion blurring and *** Codes 62P30, 97M50 Copyright © 2020, The Authors. All rights reserved.

关键词： Compressed sensing

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Investigation on mapping relationship between deflection and cable tension by artificial neural networks 11

Investigation on mapping relationship between deflection and...

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11th International Workshop on structural Health Monitoring 2017: Real-Time Material State Awareness and Data-Driven Safety Assurance, IWSHM 2017

作者： Tian, Yadi Li, Hui Key Laboratory of Intelligent Disaster Prevention and Mitigation for Civil Infrastructure Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters Ministry of Industry and Information Technology Key Laboratory of Structural Dynamic Behavior and Control School of Civil Engineering Harbin Institute of Technology Harbin150090 China

ISBN: (纸本)9781605953304

Cables usually serve as critical load-bearing structural components in cable-stayed bridges. Vertical deflection is an important overall indicator that directly reflects the health status of bridge. The relationship between cable tension and vertical deflection also reflects the underlying mechanism of structures. In this context, a machine learning-based approach is proposed. Cable tension and vertical deflection are caused by prestress, temperature and vehicle loads. In this study, we focus on the cable force and vertical deflection caused by vehicle loads. Artificial neural network (ANN) is employed as the supervised learning method to learn the relationship between cable tension and vertical deflection. Field monitored data of Jintang Bridge are used to test the validity of the proposed method. The results show that ANN is capable of modelling vertical deflection from cable tension data in the case of arbitrary vehicle distribution. The proposed method which integrates the local and global variables by using two different kinds of monitoring data, avoids the complicated mechanical derivations, and is proved to be environment-insensitive.

关键词： Neural networks

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Compressible effect on the cavitating flow:A numeric study

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Journal of Hydrodynamics 2017年第6期29卷 1089-1092页

作者：张伟柏晓东马峥陈刚 Yong Wang Science and Technology on Water Jet Propulsion Laboratory Marine Design and Research Institute of ChinaShanghai 200011China Ministry of Education Key Laboratory of Structural Dynamic Behavior and Control School of CivilEngineeringHarbin Institute of TechnologyHarbin 150090China China Ship Scientific Research Center Wuxi 214082China Max Planck Institute for Dynamics and Self-Organization Am Faflberg 17Gottingen 3 7077Germany

To understand the effect of the compressibility on the cavitating flow, a compressible, multiphase, single component Reynolds averaged Navier-Stokes（RANS） solver is used to study the cavitating flow on a wedge in the present work. A barotropic equation of status is used. A non-linear model for compressibility in the mixture is adopted to capture the effect of the compressibility within the complex cavitation bubbly mixtures. An unsteady cavitation phenomenon is found in the numerical simulation. The numerical results of local compressibility and Mach number in the bubbly mixture are given. The mechanism responsible for the unsteady shedding of the bubbly mixture is discussed based on the numerical results.

关键词： Cavitation compressibility barotropic flow

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On two asymmetry wake patterns behind two side-by-side square cylinders

On two asymmetry wake patterns behind two side-by-side squar...

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第二届全球华人水动学学术会议

作者： Wei Zhang Xiaodong Bai Science and Technology on Water Jet Propulsion Laboratory Marine design and research institute of China Ministry of Education Key laboratory of Structural Dynamic Behavior and Control School of Civil EngineeringHarbin Institute of Technology

Several asymmetric wake patterns are discovered for flow behind two side-by-side circle *** present work extends previous researches to study flow behind two side-by-side square cylinders with focus on two types of asymmetric wake flow,namely deflected oscillatory wake and flip-flop,which are believed to be of the same *** combination of the direct numerical simulation by lattice Boltzmann method(DNS-LBM) and the state-of-art dynamic mode decomposition(DMD) is used to explore the underlying physics of the *** types of asymmetric wake patterns are presented in the wake like the wake of a pair of circle *** is confirmed that the deflection of the wake is not of Coanda ***,the dynamic modes of the flows are extracted from the numerical *** comparing the corresponding modes,it is found here the two types of flow are of different mechanism.

关键词： Wake flow pattern Side-by-side cylinder DMD DNS-LBM

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Seismic fragility analysis of steel-concrete composite bridges excited by near-fault ground motions

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Tumu Gongcheng Xuebao/China Civil Engineering Journal 2016年 49卷 56-60and77页

作者： Liu, Yang Lu, Dagang Yu, Xiaohui Key Lab of Structural Dynamic Behavior and Control of China Ministry of Education Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China State Key Laboratory for Disaster Reduction in Civil Engineering Tongji University Shanghai200092 China

The seismic fragility analysis was conducted for a steel-concrete composite bridge (SCCB) including the effects of the near-fault pulse-like ground motions. A total of 60 real ground motions were selected from the PEER strong earthquake database as the inputs. The global fragility curves and local fragility curves of the bridge were obtained through the fragility analysis. Compared to the fragility results of the far-field earthquake records, it is found that the demands due to the near-fault ground motions are significantly larger than that due to the far-field ground motions. Under the near-fault pulse-like ground motions, the pier is the most fragile component, while the concrete crossbeam and the studs are less fragile. © 2016, Editorial Office of China Civil Engineering Journal. All right reserved.

关键词： Concretes

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Pounding-induced stress wave analysis and mitigation of highway bridges under earthquakes 6

Pounding-induced stress wave analysis and mitigation of high...

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Joint 6th International Conference on Advances in Experimental structural Engineering, AESE 2015 and 11th International Workshop on Advanced Smart Materials and Smart Structures Technology, ANCRiSST 2015

作者： Li, Suchao Guo, Anxin Cui, Lili Mao, Chenxi Li, Hui Ministry of Education Key Laboratory of Structural Dynamic Behavior and Control School of Civil Engineering Harbin Institute of Technology Harbin150090 China School of Civil Engineering Harbin Institute of Technology Harbin150090 China Institute of Engineering Mechanics China Earthquake Administration Harbin150090 China

Seismic colliding between adjacent structures without enough distance may lead to considerable structural damage or even collapse during large earthquakes. Additionally, during the contact-separation process, pounding-induced waves not only increase internal damage of the structure but also have significant effect on the acceleration measurement. To investigate the propagation behavior of the colliding-induced stress wave and the pounding mitigation effects of shape memory alloy pseudo-rubber shock absorber devices (SMAPR-SADs) on adjacent superstructures, a series of shaking table tests on a 1:30 scaled steel highway bridge model are performed. Then, the effect of stress waves on the acceleration signals of bridge structures is firstly investigated. The characteristics of pounding stress waves are analyzed based on wave theory, the cross wavelet transform and wavelet coherence analysis. The amplitude and absolute energy of the stress waves are compared between the original structure and after the installation of SMAPR-SADs. Furthermore, the mitigation mechanism of SMAPR-SADs on pounding-induced stress waves is interpreted. Results show that SMAPR-SAD has stable energy absorption ability and could obviously reduce the amplitude and energy of the pounding stress waves, and also lower the corresponding effect on the accuracy of the measurement system. © International Conference on Advances in Experimental structural Engineering. All rights reserved.

关键词： Shock absorbers

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Experimental validation of a signal-based approach for structural earthquake damage detection using fractal dimension of time frequency feature

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Earthquake Engineering and Engineering Vibration 2014年第4期13卷 671-680页

作者： Tao Dongwang Mao Chenxi Zhang Dongyu Li Hui Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering Mechanics China Earthquake Administration Key Lab of Structures Dynamic Behavior and Control (Harbin Institute of Technology) Ministry of Education Center of Structural Monitoring and Control School of Civil Engineeing Harbin Institute of Technology

This article extends a signal-based approach formerly proposed by the authors, which utilizes the fractal dimension of time frequency feature （FDTFF） of displacements, for earthquake damage detection of moment resist frame （MRF）, and validates the approach with shaking table tests. The time frequency feature （TFF） of the relative displacement at measured story is defined as the real part of the coefficients of the analytical wavelet transform. The fractal dimension （FD） is to quantify the TFF within the fundamental frequency band using box counting method. It is verified that the FDTFFs at all stories of the linear MRF are identical with the help of static condensation method and modal superposition principle, while the FDTFFs at the stories with localized nonlinearities due to damage will be different from those at the stories without nonlinearities using the reverse-path methodology. By comparing the FDTFFs of displacements at measured stories in a structure, the damage-induced nonlinearity of the structure under strong ground motion can be detected and localized. Finally shaking table experiments on a 1：8 scale sixteen-story three-bay steel MRF with added frictional dampers, which generate local nonlinearities, are conducted to validate the approach.

关键词： earthquake damage detection time frequency feature fractal dimension signal-based shaking table test frictional damper

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