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A machine learning based solver for pressure Poisson equations

Theoretical & Applied Mechanics Letters 2022年第5期12卷 315-321页

作者： Ruilin Chen Xiaowei Jin Hui Li Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of TechnologyHarbin 150090China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of TechnologyHarbin 150090China Guangdong-Hong Kong-Macao Joint Laboratory for Data-Driven Fluid Mechanics and Engineering Applications Harbin Institute of Technology(Shenzhen)Shenzhen 518055China

When using the projection method(or fractional step method)to solve the incompressible Navier-Stokes equations,the projection step involves solving a large-scale pressure Poisson equation(PPE),which is computationally expensive and *** this study,a machine learning based method is proposed to solve the large-scale *** machine learning(ML)-block is used to completely or partially(if not sufficiently accurate)replace the traditional PPE iterative solver thus accelerating the solution of the incompressible Navier-Stokes *** ML-block is designed as a multi-scale graph neural network(GNN)framework,in which the original high-resolution graph corresponds to the discrete grids of the solution domain,graphs with the same resolution are connected by graph convolution operation,and graphs with different resolutions are connected by down/up prolongation *** well trained MLblock will act as a general-purpose PPE solver for a certain kind of flow *** proposed method is verified via solving two-dimensional Kolmogorov flows(Re=1000 and Re=5000)with different source *** the premise of achieving a specified high precision(ML-block partially replaces the traditional iterative solver),the ML-block provides a better initial iteration value for the traditional iterative solver,which greatly reduces the number of iterations of the traditional iterative solver and speeds up the solution of the *** experiments show that the ML-block has great advantages in accelerating the solving of the Navier-Stokes equations while ensuring high accuracy.

关键词： Pressure Poisson equation Machine learning Projection method Multi-scale GNN

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Experimental investigation on the impingement of synthetic jet vortex rings on a spherical wall

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Physical Review Fluids 2022年第4期7卷 044703-044703页

作者： Changlong Chen Donglai Gao Wen-Li Chen Key Laboratory of Smart Prevention and Mitigation of Civil Engineering Disasters The Ministry of Industry and Information Technology Harbin Institute of Technology Harbin 150090 China Key Laboratory of Structures Dynamic Behavior and Control The Ministry of Education Harbin Institute of Technology Harbin 150090 China

An experimental study was conducted to investigate the influence of sphere diameter and Reynolds number on synthetic jet vortex rings impinging on a spherical wall. Laser-induced fluorescence and two-dimensional particle image velocimetry techniques were applied to visualize flow and measure flow velocity, respectively. In this experiment, the stroke length was kept constant (L=3.6), and different diameters (d/D=1, 6, and 16) and Reynolds numbers (Resj=227 and 682) were analyzed. In addition to flow visualization images and phase-averaged λci fields, the vortex ring trajectories and circulation are presented to reveal the evolution features of the vortex rings. The results demonstrated that the Reynolds number mainly determined the strength and induced ability of the primary vortex ring (PVR) and the sphere-diameter effect was reflected by the expansion distance of the PVR and its separation from the wall boundary layer. It was found that only a secondary vortex ring (SVR) was induced in the case of a small diameter or a low Reynolds number. As the diameter and Reynolds number increased, the PVR expanded continuously along the wall and induced a SVR and tertiary vortex ring. In particular, driven by the curve, the strength of the induced vortex ring decreased with the increase in the sphere diameter.

关键词： Vortex flows Wakes & jets

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Analysis of measured data of snow loads on roof with parapets based on comparison of foreign codes

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Jianzhu Jiegou Xuebao/Journal of Building Structures 2019年第6期40卷 32-39页

作者： Zhang, Guolong Zhang, Qingwen Mo, Huamei Fan, Feng Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China Key Laboratory of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China

In the calculation of the snow load on the roof with parapets, standards of Japan, America, and Europe have given full consideration to the erosion effect on the snow load of the fully exposed roof caused by wind field, the movement of snow induced by wind, the supplementation of upstream snow to snow heaped up around downstream obstruction. In addition, factors such as the indoor heating and the combined effect of rain and snow are introduced to realize an accurate estimation of snow load on building roofs. By contrast, the Chinese code only considers the influence of the parapet height. Therefore, based on the measured snow distribution on an actual parapet roof on ages and the influencing factors in foreign codes introduced above, the snow distribution characteristics on the parapet roof were analyzed. The results show that: more snow is blown downstream towards the parapet;the peak snow depth close to the downstream parapet is proportional to the upstream roof width, and with an increasing wind velocity, the drifting effect is enhanced;the upstream roof width and the ground snow load have a great influence on the peak snow depth at the parapet, and the influence of wind velocity depends on the ground snow load;the larger the ground snow load is, the greater influence the wind velocity has;the ratio of the snowdrift length to the parapet height is around 3.75, and it is suggested to adopt a value of 4.0 in Chinese code. © 2019, Editorial Office of Journal of Building Structures. All right reserved.

关键词： Roofs

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Ordered mesoporous carbon as an efficient heterogeneous catalyst to activate peroxydisulfate for degradation of sulfadiazine

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Chinese Chemical Letters 2022年第5期33卷 2747-2752页

作者： Zhi-Ling Li Di Cao Hao Cheng Fan Chen Jun Nan Bin Liang Kai Sun Cong Huang Ai-Jie Wang State Key Laboratory of Urban Water Resource and Environment School of EnvironmentHarbin Institute of TechnologyHarbin 150090China School of Civil&Environmental Engineering Harbin Institute of Technology(Shenzhen)Shenzhen 518055China School of Ecology and Environment Northwestern Polytechnical UniversityXi’an 710129China Key Lab of Structures Dynamic Behavior and Control of China Ministry of Education School of Civil EngineeringHarbin Institute of TechnologyHarbin 150090China National Technology Innovation Center of Synthetic Biology Tianjin Institute of Industrial BiotechnologyChinese Academy of SciencesTianjin 300308China

Catalytic potential of carbon nanomaterials in peroxydisulfate(PDS)advanced oxidation systems for degradation of antibiotics remains poorly *** study revealed ordered mesoporous carbon(type CMK)acted as a superior catalyst for heterogeneous degradation of sulfadiazine(SDZ)in PDS sys-tem,with a first-order reaction kinetic constant(k)and total organic carbon(TOC)mineralization efficiency of 0.06 min^(–1) and 59.67%±3.4%within 60min,*** catalyzed PDS system exhibited high degradation efficiencies of five other sulfonamides and three other types of antibiotics,verifying the broad-degradation capacity of *** neutral pH conditions,the optimal catalytic parameters were an initial SDZ concentration of 44.0mg/L,CMK dosage of 0.07g/L,and PDS dosage of 5.44mmol/L,respectively.X-ray photoelectron spectroscopy and Raman spectrum analysis confirmed that the defect structure at edge of CMK and oxygen-containing functional groups on surface of CMK were major active sites,contributing to the high catalytic *** radical quenching analysis revealed that both SO_(4)•−and•OH were generated and participated in catalytic *** addition,direct electron transfer by CMK to activate PDS also occurred,further promoting catalytic *** of SDZ molecule was optimized using density functional theory,and the possible reaction sites in SDZ molecule were calculated using Fukui *** ultra-high-performance liquid chromatography(UPLC)–mass spectrometry(MS)/MS analysis,three potential degradation pathways were proposed,including the direct removal of SO_(2)molecules,the 14S-17N fracture,and the 19C-20N and 19C-27N cleavage of the SDZ *** study demonstrated that ordered mesoporous carbon could work as a feasible catalytic material for PDS advanced oxidation during removal of antibiotics from wastewater.

关键词： Ordered mesoporous carbon CMK Sulfadiazine Peroxydisulfate Degradation pathway Density functional theory Physicochemical properties

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Bayesian system identification based on hierarchical sparse Bayesian learning and gibbs sampling with application to structural damage assessment

arXiv

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arXiv 2017年

作者： Huang, Yong Beck, James L. Li, Hui Key Lab of Structural Dynamic Behavior and Control of the Ministry of Education School of Civil Engineering Harbin Institute of Technology Harbin China Division of Engineering and Applied Science California Institute of Technology CA United States

Bayesian system identification has attracted substantial interest in recent years for inferring structural models based on measured dynamic response from a structural dynamical system. The focus in this paper is Bayesian system identification based on noisy incomplete modal data where we can impose spatially-sparse stiffness changes when updating a structural model. To this end, based on a similar hierarchical sparse Bayesian learning model from our previous work, we propose two Gibbs sampling algorithms. The algorithms differ in their strategies to deal with the posterior uncertainty of the equation-error precision parameter, but both sample from the conditional posterior probability density functions (PDFs) for the structural stiffness parameters and system modal parameters. The effective dimension for the Gibbs sampling is low because iterative sampling is done from only three conditional posterior PDFs that correspond to three parameter groups, along with sampling of the equation-error precision parameter from another conditional posterior PDF in one of the algorithms where it is not integrated out as a "nuisance" parameter. A nice feature from a computational perspective is that it is not necessary to solve a nonlinear eigenvalue problem of a structural model. The effectiveness and robustness of the proposed algorithms are illustrated by applying them to the IASE-ASCE Phase II simulated and experimental benchmark studies. The goal is to use incomplete modal data identified before and after possible damage to detect and assess spatially-sparse stiffness reductions induced by any damage. Our past and current focus on meeting challenges arising from Bayesian inference of structural stiffness serve to strengthen the capability of vibration-based structural system identification but our methods also have much broader applicability for inverse problems in science and technology where system matrices are to be inferred from noisy partial information about their eigenq

关键词： Probability density function

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引用

Physical Review Fluids 2024年第5期9卷 054608-054608页

作者： Xue-Lu Xiong (熊雪露) Shujin Laima (赖马树金) Hui Li (李惠) Yi Zhou (周毅) School of Energy and Power Engineering Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Guangdong-Hong Kong-Macao Joint Laboratory for Data-Driven Fluid Mechanics and Engineering Applications

This paper presents a quadrant analysis of turbulent rotor wakes, placing a particular emphasis on the self-similarity in single-point turbulent statistics. The self-similarity analysis reveals that within the wake self-similar region, the distribution of the Reynolds shear stress −u′v′¯ and the turbulent kinetic energy k in different quadrants can also attain a state of self-similarity. The length scaling is the same for −u′v′¯, k, and their different quadrant contributions. However, the velocity scaling of the ejection contribution differs from that of −u′v′¯ and k. Additionally, the analysis of hole filtering and spectrum filtering effects on the self-similarity and scaling of the ejection contribution to −u′v′¯ reveals a strong connection between ejection events and large-scale coherent structures, as well as deceleration extreme events. This finding is further confirmed through quadrant analysis of the time evolution of velocity fluctuations. The present study can be helpful in improving our understanding of the turbulent wake self-similarity.

关键词： Shear flows Wakes & jets

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Three-Dimensional Reconstruction and Monitoring of Large-Scale Structures via Real-Time Multi-vision System 11th

Three-Dimensional Reconstruction and Monitoring of Large-Sca...

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11th International Symposium on Intelligence Computation and Applications, ISICA 2019

作者： Tang, Yunchao Chen, Mingyou Wu, Xiangguo Huang, Kuangyu Wu, Fengyun Zou, Xiangjun He, Yuxin College of Urban and Rural Construction Zhongkai University of Agriculture and Engineering Guangzhou510225 China Key Laboratory of Key Technology on Agricultural Machine and Equipment College of Engineering South China Agricultural University Guangzhou510642 China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education and School of Civil Engineering Harbin Institute of Technology Harbin150001 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China

ISBN: (纸本)9789811555763

A four-ocular vision system is proposed for the three-dimensional (3D) reconstruction of large-scale concrete-filled steel tube (CFST) materials under complex testing conditions. These measurements are vitally important for evaluating the seismic performance and 3D deformation of large-scale specimens. A four-ocular vision system is constructed to sample the large-scale CFST, then point cloud acquisition, filtering, and stitching algorithms are applied to obtain 3D point cloud of the specimen surface. Novel point cloud correction algorithms based on geometric features and deep learning are proposed to correct the coordinates of the stitched point cloud. The proposed algorithms center on the stitching error of the multi-view point cloud and the geometric and spatial characteristics of the targets for error compensation, which makes them highly adaptive and efficient. A high-accuracy multi-view 3D model for the purposes of real-time complex surface monitoring can be obtained via this method. Performance indicators of the two algorithms were evaluated on actual tasks. The cross-section diameters at specific heights in the reconstructed models were calculated and compared against laser range finder data to test the performance of the proposed method. A visual tracking test on a CFST under cyclic loading shows that the reconstructed output well reflects the complex 3D surface after point cloud correction and meets the requirements for dynamic monitoring. The proposed method is applicable to complex environments featuring dynamic movement, mechanical vibration, and continuously changing features. © 2020, Springer Nature Singapore Pte Ltd.

关键词： Vibrations (mechanical)

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Experimental and Numerical Study on dynamic Responses of a Tlp-Type Modular Floating Structure System

SSRN

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SSRN 2024年

作者： Li, Yanwei Ren, Nianxin Cai, Wenyu Liu, Yaqiong Ou, Jinping School of Marine Science and Engineering Hainan University Haikou570228 China State Key Laboratory of Marine Resource Utilization in South China Sea Hainan University Haikou570228 China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education China

This paper explores a proposed TLP-type modular floating structure system, incorporating both central TLP modules and peripheral floating artificial reef modules. The outermost floating artificial reef module can function as a floating breakwater, and also serving as a habitat for surrounding marine organisms. Both scale model tests (1:80) and time-domain numerical simulations were performed. The simulations accounted for hydrodynamic interactions among the bodies and the mechanical coupling effects. During the scale model test, a survival strategy has been proposed to prevent collision risks between reef modules and adjacent TLP modules. A preliminary stiffness recommendation was suggested by a trade-off between the pitch of the reef module and the spring force. Numerical and experimental results have been widely compared and discussed. A good agreement has been achieved, although responses are slightly overestimated by numerical simulation due to the neglect of the viscous damping effect. In addition, the responses of the proposed system, connected with and without the outermost floating artificial reef module, have been compared and analyzed. The results suggest that the connection of the reef module can significantly reduce the system's surge response and enhance its survivability under severe sea conditions. © 2024, The Authors. All rights reserved.

关键词： dynamic response

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Study on the performance of reinforced concrete blocks treated by styrene-acrylic emulsion

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Chemical Engineering Transactions 2018年 66卷 85-90页

作者： Zhu, Jing Zheng, Wenzhong Xie, Lili Wu, Yunqiang Zhang, Yongxin Fu, Junxiang Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering Mechanics China Earthquake Administration Harbin150080 China College of Civil Engineering and Architecture Harbin University of Science and Technology Harbin150080 China Key Lab of Structures Dynamic Behavior and Control of the Ministry Education Harbin Institute of Technology Harbin150090 China

This paper introduces a method of improving the performance of reinforced concrete blocks and reveals the reinforcing effect of fibers. It is pointed out that the plant fibers treated by styrene-acrylic emulsion can effectively improve the interfacial bonding conditions, for the modified straw fibers which were treated by alkali processing and acrylic coating, their performance has been significantly improved, which is conducive to absorbing energy and improving the strength of the material. This paper focuses on introducing three types of reinforced concrete blocks, it’s known that the bridging effect can effectively prevent the development of micro cracks. The occurrence of cracks increases the macroscopic tensile strain of the material and increases the ductility and toughness of the matrix. Studying plant fiber reinforced blocks will help promote the application of this new wall materials. Copyright © 2018, AIDIC Servizi S.r.l.

关键词： Tensile strain

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Research on Local Heating Technology in Extremely Low Temperature Environment Based on Thermal Comfort and CFD 18

Research on Local Heating Technology in Extremely Low Temper...

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18th IBPSA Conference on Building Simulation, BS 2023

作者： Wang, Zhen Zhang, Yuanyuan Gao, Hu Xia, Yun Wu, Yue Liu, Jing School of Architecture Harbin Institute of Technology Heilongjiang Harbin150006 China Key Laboratory of Cold Region Urban and Rural Human Settlement Environment Science and Technology Ministry of Industry and Information Technology China Heilongjiang Province Academy of Cold Area Building Research Heilongjiang Harbin150080 China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of Technology Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China

This paper investigated the effect of personal heating technology on human thermal comfort and skin temperature in extremely low temperature environment. Four subjects carried out personal heating experiments in a low temperature laboratory at around -21°C. Personal heating equipment includes heating glove, heating cushion, heating mat and airwarmer. In order to maximize the thermal comfort of personnel, this paper designed an efficient local heating system based on airwarmer and heating mat. At the same time, in order to better evaluate the thermal comfort of personnel in an extremely low temperature environment, an improved one-dimensional stolwijk human thermoregulation model(HTM) was established. By combining it with CFD, the influence of the airwarmer on the thermal comfort of personnel and skin temperature was simulated. This method can be used to assess the overall thermal sensation and thermal comfort of personnel in extremely low temperature environment. © 2023 *** rights reserved.

关键词： Thermal comfort

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