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Heat transfer and flow structure in centrally-confined 2-D Rayleigh-Bénard convection

Journal of Hydrodynamics 2024年第4期36卷 772-780页

作者： Cong Sun Jian-zhao Wu Xiao-hui Meng Cai-xi Liu Wei Xu Yu-hong Dong Quan Zhou Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai Key Laboratory of Mechanics in Energy EngineeringShanghai UniversityShanghai200072China China Electrical Equipment Group Research Institute of Science and Technology Co.Ltd. Shanghai200072China

Through direct numerical simulations,we investigated the flow structure and heat transfer of the centrally confined 2-D Rayleigh-Bénard(RB)convection over the Rayleigh number range 9×10^(5)≤Ra≤10^(9) at a fixed Prandtl number Pr=*** is found that with increasing Ra,the number of convection rolls in the central vertical channel increases from zero to *** there is no rolls in the vertical channel,the convective flow in central region is significantly influenced by the boundary layer,whereas when the convection rolls is generated in the vertical channel,the convective flows in central regions is free from the boundary layer limitation,and by defining the characteristic length,one obtains the heat transfer scaling law relation in vertical channel,i.e.,Nu_(vc)∼Ra_(vc)^(0.476±0.005),which could be the evidence of“ultimate regime”.

关键词： Rayleigh-Benard(RB)turbulence heat transport vertical channel ultimate regime

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A dive into spectral inference networks: improved algorithms for self-supervised learning of continuous spectral representations

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applied Mathematics and mechanics(English Edition) 2023年第7期44卷 1199-1224页

作者： J.WU S.F.WANG P.PERDIKARIS Graduate Group in Applied Mathematics and Computational Science University of Pennsylvania PhiladelphiaPA 19104U.S.A. Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania PhiladelphiaPA 19104U.S.A.

We propose a self-supervising learning framework for finding the dominant eigenfunction-eigenvalue pairs of linear and self-adjoint *** represent target eigenfunctions with coordinate-based neural networks and employ the Fourier positional encodings to enable the approximation of high-frequency *** formulate a self-supervised training objective for spectral learning and propose a novel regularization mechanism to ensure that the network finds the exact eigenfunctions instead of a space spanned by the ***,we investigate the effect of weight normalization as a mechanism to alleviate the risk of recovering linear dependent modes,allowing us to accurately recover a large number of *** effectiveness of our methods is demonstrated across a collection of representative benchmarks including both local and non-local diffusion operators,as well as high-dimensional time-series data from a video *** results indicate that the present algorithm can outperform competing approaches in terms of both approximation accuracy and computational cost.

关键词： spectral learning partial differential equation(PDE) neural network slow features analysis

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A human-sensitive frequency band vibration isolator for heavy-duty truck seats

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applied Mathematics and mechanics(English Edition) 2024年第10期45卷 1733-1748页

作者： Qingqing LIU Shenlong WANG Ge YAN Hu DING Haihua WANG Qiang SHI Xiaohong DING Huijie YU School of Mechanical Engineering University of Shanghai for Science and TechnologyShanghai 200093China State Key Laboratory of Mechanical System and Vibration School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Frontier Science Center of MechnoinformaticsShanghai Institute of Applied Mathematics and MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China Yanfeng Adient Seating Co. Ltd.Shanghai 201315China College of Mechanical and Electrical Engineering Jiaxing Nanhu UniversityJiaxing 314001Zhejiang ProvinceChina

In this study,a human-sensitive frequency band vibration isolator(HFBVI)with quasi-zero stiffness(QZS)characteristics for heavy-duty truck seats is designed to improve the comfort of heavy-duty truck drivers on uneven ***,the analytical expressions for the force and displacement of the HFBVI are derived with the Lagrange equation and d'Alembert's principle,and are validated through the prototype restoring force ***,the harmonic balance method(HBM)is used to obtain the dynamic responses under harmonic excitation,and further the influence of pre-stretching on the dynamic characteristics and transmissibility is ***,the experimental prototype of the HFBVI is fabricated,and vibration experiments are conducted under harmonic excitation to verify the vibration isolation performance(VIP)of the proposed vibration *** experimental results indicate that the HFBVI can effectively suppress the frequency band(4-8 Hz)to which the human body is sensitive to vertical *** addition,under real random road spectrum excitation,the HFBVI can achieve low-frequency vibration isolation close to 2 Hz,providing new prospects for ensuring the health of heavy-duty truck drivers.

关键词： human-sensitive frequency band quasi-zero stiffness(QZS) heavy-duty truck seat real random road spectrum low-frequency vibration isolation

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Modeling,analysis,and simulation of X-shape quasi-zero-stiffness-roller vibration isolators

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applied Mathematics and mechanics(English Edition) 2022年第7期43卷 1027-1044页

作者： Xiaoye MAO Mengmeng YIN Hu DING Xiaofeng GENG Yongjun SHEN Liqun CHEN Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200444China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China

Existing quasi-zero stiffness(QZS)isolators are *** terms of their advantages,a novel X-shape QZS isolator combined with the cam-roller-spring mechanism(CRSM)is *** from the existing X-shape isolators,oblique springs are used to enhance the negative stiffness of the ***,the CRSM is used to eliminate the gravity of the loading mass,while the X-shape structure leaves its static *** existing QZS isolators are demonstrated and classified according to their nonlinearity mechanisms and classical *** is shown that the oblique spring can realize negative stiffness based on the simplest *** X-shape has a strong capacity of loading mass,while the CRSM can achieve a designed restoring force at any *** proposed isolator combines all these advantages *** on the harmonic balance method(HBM)and the simulation,the displacement transmissibilities of the proposed isolator,the X-shape isolators just with oblique springs,and the X-shape isolators in the traditional form are *** results show that the proposed isolator has the lowest beginning isolation frequency and the smallest maximum displacement ***,it still has some disadvantages similar to the existing QZS *** means that its parameters should be designed carefully so as to avoid becoming a bistable system,in which there are two potential wells in the potential energy curve and thus the isolation performance will be worsened.

关键词： quasi-zero stiffness(QZS) cam-roller X-shape isolator nonlinear isolation

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The Scheme to Determine the Convergence Term of the Galerkin Method for Dynamic Analysis of Sandwich Plates on Nonlinear Foundations

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Acta Mechanica Solida Sinica 2021年第1期34卷 1-11页

作者： Hong-Yan Chen Hu Ding Shao-Hua Li Li-Qun Chen Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai Institute of Applied Mathematicsand MechanicsSchool of Mechanics and Engineering ScienceShanghai UniversitygShanghai 200444China State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversitxyShiyiazhuang 050043China

The vibration of a plate resting on elastic foundations under a moving load is of great significance in the design of many engineering fields,such as the vehicle-pavement system and the aircraft-runway *** or runways are always laminated *** Galerkin truncation method is widely used in the research of *** number of truncation terms directly affects the convergence and accuracy of the response ***,the selection of the number of truncation terms has not been clearly stated.A nonlinear viscoelastic foundation model under a moving load is *** on the natural frequency of linear undisturbed derivative systems,the truncation terms are used to determine the convergence of vibration *** criterion for the convergence of the Galerkin truncation term is *** scheme is related to the natural frequency with high efficiency and *** the dynamic response of the sandwich beam under a moving load,the feasibility of the scheme is *** effects of different system parameters on the scheme and the truncation convergence of dynamic response are *** research in this paper can be used as a reference for the study of the vibration of elastic foundation ***,the model established and the truncation analysis method proposed are helpful for studying the vibration of vehicle-pavement system and related systems.

关键词： ndwich plate Galerkin method Convergence Nonlinear foundation

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Deformation and annealing of brass

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Materials Today: Proceedings 2022年 64卷 1380-1383页

作者： Gaurav Chakraborty, Purnashis Prasad Vejendla, S.B. Department of Mechanical Engineering KIET Group of Institutions Ghaziabad 201206 India Department of Applied Mechanics IIT Delhi New Delhi 110016 India Department of Materials Science and Engineering IIT Delhi New Delhi 110016 India

In the present investigation, the deformation behaviour and annealing of brass have been studied. The brass samples were rolled at ambient temperature and subsequently annealed at 420 °C, 520 °C and 620 °C for 30 min. This work aims to study the hardness variation with different percentage reductions in the thickness of the brass. The hardness variation has been correlated with the microstructure evolution of the annealed brass specimen. The work findings demonstrate that the cold rolling progresses, increases in hardness value and grain shape changes. As the annealing temperature increased, the drop in hardness was noticed. © 2022

关键词： Hardness

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Numerical Simulation of Train-Induced Structural Vibration 2

Numerical Simulation of Train-Induced Structural Vibration

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2nd International Conference on Advances in Modern Physics sciences and engineering Technology, ICPSET 2023

作者： Lin, Gang Liu, Donghuan China Energy Engineering Group Guangdong Electric Power Design Institute Co. Ltd. Guangzhou510663 China Department of Applied Mechanics University of Science and Technology Beijing Beijing100083 China

Train-induced structural vibration caused more and more attentions nowadays, and the present paper developed a numerical approach of train-induced structural vibration simulation with ANSYS software. The finite element model is composed by buildings, rail, sleepers, ballast and several layers of soil, and the moving load is represented by wheel-rail coupling forces, and both solid element, shell element and beam element are used in the finite element model. Acceleration time history and vibration levels of the key point on the buildings are given, and effect of different wheel-rail coupling forces and the dynamic response of the building are also numerically investigated. Comparisons of free boundary, symmetric boundary, fixed boundary and transmitting boundary conditions on the dynamic responses are also illustrated. Numerical results show that, both boundary condition and load type could affect the dynamic response of the structures near the train tracks, and validation test should be performed firstly to determine the proper boundary condition and load amplitude and frequency. The proposed numerical method provides a powerful technic tool for numerically predicting the dynamic response of train-induce structural vibration, and could also be employed to evaluate the vibration control results of different approaches. © Published under licence by IOP Publishing Ltd.

关键词： Dynamic response

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Design and implementation of a low-cost non-invasive modular kit for wheelchairmotorization in developing countries 31

Design and implementation of a low-cost non-invasive modular...

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31st IEEE International Conference on Electronics, Electrical engineering and Computing, INTERCON 2024

作者： Valladolid-Ballon, Anthony Flores-Oscanoa, Jesus Revilla-Segovia, Richard Kevin Astete-Florez, Brayan Yordy Lavayen-Farfan, Daniel Fosca-Pastor, Carlos Pontificia Universidad Católica del Perú Faculty of Science and Engineering Lima Peru Pontificia Universidad Católica del Perú Applied Mechanics Machines and Mechanisms Research Group Mechanical Engineering Section Lima Peru Pontificia Universidad Católica del Perú Mechanical Engineering Section Lima Peru

ISBN: (纸本)9798350378344

Wheelchairs are essential for people with reduced mobility. Motorization of these devices can provide an increase quality of living and independence for their users. However, the cost of electric wheelchairs makes them inaccessible to users from developing countries. To address this issue, a low-cost modular kit is proposed, designed and manufactured. The mechatronic design of the kit includes the mechanical design of the components as well as dimensioning, the selection of electronic components, as well as the incorporation of IoT technology to be able to control it using a smartphone if necessary. The resulting modular kit proves to be useful as it can be rapidly installed on a commercial wheelchair without modifying its structure. Preliminary tests of the functional prototype show the wheelchair can provide enhanced mobility to the user, a low turning radius for narrow spaces, as wells as the ability to easily climb up and down on ramps. © 2024 IEEE.

关键词： Wheelchairs

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Functional hydrogel coatings

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National science Review 2021年第2期8卷 151-169页

作者： Junjie Liu Shaoxing Qu Zhigang Suo Wei Yang Center for X-Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province and Department of Engineering MechanicsZhejiang University State Key Laboratory of Fluid Power and Mechatronic System Zhejiang University Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong University John A.Paulson School of Engineering and Applied Sciences Kavli Institute for Bionano Science and TechnologyHarvard University

Hydrogels—natural or synthetic polymer networks that swell in water—can be made mechanically,chemically and electrically compatible with living tissues. There has been intense research and development of hydrogels for medical applications since the invention of hydrogel contact lenses in 1960. More recently,functional hydrogel coatings with controlled thickness and tough adhesion have been achieved on various substrates. Hydrogel-coated substrates combine the advantages of hydrogels, such as lubricity,biocompatibility and anti-biofouling properties, with the advantages of substrates, such as stiffness,toughness and strength. In this review, we focus on three aspects of functional hydrogel coatings:(i) applications and functions enabled by hydrogel coatings,(ii) methods of coating various substrates with different functional hydrogels with tough adhesion, and(iii) tests to evaluate the adhesion between functional hydrogel coatings and substrates. Conclusions and outlook are given at the end of this review.

关键词： hydrogel coatings coating methods coating tests adhesion hydrogel applications

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Effect of Filler Content on Flexural and Viscoelastic Properties of Coir Fibers and Argania Nut-shells Reinforced Phenolic Resin Composites

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Journal of Bionic engineering 2022年第6期19卷 1886-1898页

作者： Hala Bensalah Marya Raji Kamal Gueraoui Abdelazziz Khtira Hamid Essabir Rachid Bouhfid Abou el kacem Qaiss Group of Mechanics and Materials Energy Research CenterFaculty of ScienceMohammed V University in Rabat10100RabatMorocco Composites and Nanocomposites Center Moroccan Foundation for Advanced ScienceInnovation and Research(MAScIR)10100RabatMorocco Mohammed Ⅵ Polytechnic University Lot 660 Hay Moulay Rachid43150Ben GuerirMorocco Group of Simulation in Mechanics and Energy Energy Research CenterFaculty of ScienceMohammed Ⅴ University10100RabatMorocco Group of Semiconductors and Environmental Sensor Technologies Energy Research CenterFaculty of ScienceMohammed V University10100RabatMorocco Mechanic Materials and Composites(MMC) Laboratory of Energy EngineeringMaterials and SystemsNational School of Applied Sciences of AgadirIbn Zohr University80000AgadirMorocco

The characteristics of two different kinds of lignocellulosic materials(vegetable fillers)with two morphologies as Argania nut-shells(ANS)particles and Coir Fibers(CF)were used as reinforcement for phenolic resin(Bakelite)in this work,and the composite are studied as a function of filler types,shape,content(10,20,and 30%***)and manufacturing loading force(1500 and 3000 LBs).Compression molding was used to create the composites,which were then evaluated using Scanning electronic microscopy(SEM),Fourier-transform infrared spectroscopy(FTIR),bending,dynamic-mechanical-thermal and rheological *** morphology of broken samples demonstrates that both fillers are well dispersed and *** fillers are added to the matrix,the flexural characteristics improve,and the optimal values are attained in the case of Argania *** results showed that the kind and shape of the fillers had a direct influence on the dynamic mechanical characteristics of the composites due to the reinforcement's modulus *** was noticed that,the increment of manufacturing loading force decreased the mechanical and dynamical properties of *** optimum properties obtained indicate that the composites can only be manufactured at low manufacturing loading force(1500 LBs).

关键词： Phenolic resin composites Bionic materials Coir Fibers Argania nut-shells Dynamical mechanical properties Rheological properties

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