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SUPERCAVITY MOTION WITH inertial force IN THE VERTICAL PLANE

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Journal of Hydrodynamics 2012年第5期24卷 752-759页

作者： YU Kai-ping ZOU Wang ARNDT Roger ZHANG Guang School of Astronautics Harbin Institute of TechnologyHarbin 150001China Saint Anthony Falls Laboratory University of MinnesotaMinneapolisUSA

The curvilinear motion in a vertical plane is one of the most important features of the supercavitating vehicle. It is of great significance to study the controllability and the maneuverability of the supercavitating vehicle. Models are built for the effects of the angle of attack, the gravity and the inertial force in the curvilinear motion in the vertical p｜ane. Numerica~ simulations are carried out for the supercavity motion based on these models combined with the Logvinovich model. It is shown that the maximum deviation displacement in the outward normal direction of the trajectory with a constant curvature, which occurs in the tail of the supercavity, increases as the cavitation number or the curvature radius of the supercavity trajectory decreases under the condition that other model and flow parameters are kept constant. For a varied curvature, the supercavity shape changes evidently because of the change of the ambient pressure, but with the same trend as in constant curvature. The deviation displacement increases along the supercavity length gradually.

关键词： supercavity inertial force curvilinear motion curvature radius

Design and identification of a double-acting piezoelectric-hydraulic hybrid actuator

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Chinese Journal of Aeronautics 2024年第3期37卷 456-467页

作者： Junjian ZHANG Zhihua FENG Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes University of Science and Technology of ChinaHefei 230026China

Traditional single-acting piezoelectric-hydraulic hybrid actuators usually have the problem of inertial force caused by flow pulsation of the liquid,which degrades their output *** suppress or solve the associated inertial force and enhance its output capabilities,this paper proposes a new type of double-acting piezoelectric-hydraulic hybrid actuator with four check valves acting as mechanical *** new hybrid actuator was fabricated and its output performance was *** the voltage is 700 Vp-pand the bias pressure is 2 MPa,the pulsation ratesδof the new actuator at 400 Hz,500 Hz and 600 Hz are 2.29,2.08 and 1.78,respectively,whileδof the single-acting hybrid actuator under the same conditions are 10.98,11.05 and ***,the liquid pulsation rate of the new hybrid actuator is significantly reduced,which is beneficial for improving the flow uniformity and weakening the influence of inertial force on the hybrid *** strategy ultimately leads to a maximum no-load velocity of 168.1 mm/s at 600 Hz and a maximum blocking force of 141 N at 450 Hz for the new hybrid *** addition,this strategy has the potential to be used in other electrohydrostatic actuators to improve their performance.

关键词： Double-acting Flow pulsation inertial force Piezoelectric actuators Piezoelectric devices Piezoelectric hydraulic actuation Piezoelectric pump

Mechanism and experimental study on the fruit detachment of Chinese wolfberry through reciprocating vibration

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International Journal of Agricultural and Biological Engineering 2024年第2期17卷 47-58页

作者： Song Mei Jinpeng Wang Zhiyu Song Dunbing Tang Cheng Shen College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Nanjing Research Institute for Agricultural Mechanization Ministry of Agriculture and Rural AffairsNanjing 210014China Nanjing Forestry University Nanjing 210037China

In order to realize the efficient and high-quality mechanical picking for Chinese wolfberry,firstly,the forced reciprocating vibration picking principle of the Chinese wolfberry branch was studied,and the mechanical model of vibration picking was established based on the simplified cantilever model,and the response analysis and solution of all positions for the branch were carried *** the same time,the critical mechanical model of fruit detachment under the condition of fruit hanging on branches was established,and the theoretical values of inertia force for each component of the branch were ***,through actual measurement and finite element modeling,the natural frequency and forced vibration response simulation for each component of the branch of Chinese wolfberry terminal branch model were both studied,and the relationship between single-point periodic excitation force and high-quality fruit shedding parameters was ***,according to the conclusion of the picking model,a test bench with many groups of adjustable parameters was ***,the last branch of fruit-hanging Chinese wolf berry for Ningqi No.1 was taken as the experimental object,a four-level orthogonal experiment was designed with three factors:frequency,amplitude and entrance ***,the net picking rate,damage rate and false picking rate were taken as the evaluating indicators,referring to the comprehensive scores of the three *** was concluded that the primary and secondary relations of factors affecting the picking effect are frequency,amplitude and entrance angle,and the best operation parameters are frequency of 20 Hz,amplitude of 15 mm,and entrance angle of 45°,then,a hand-held vibration picker with setting parameters was trial-produced,and the optimal parameter combination was verified in the Chinese wolfberry planting base of the National Chinese wolfberry Engineering and Technology Research *** results showed that the net picking rate of rip

关键词： Chinese wolfberry branches reciprocating vibration inertial force orthogonal experiment

Study of aerodynamic and inertial forces of a experimental and numerical methods

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Chinese Journal of Aeronautics 2022年第6期35卷 63-76页

作者： Xiaowu YANG Bifeng SONG Wenqing YANG Dong XUE Yang PEI Xinyu LANG School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical UniversityXi’an 710072China Research&Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518057China

The force-generation mechanism of a dovelike flapping-wing micro air vehicle was studied by numerical simulation and *** obtain the real deformation pattern of the flapping wing,the digital image correlation technology was used to measure the dynamic deformation of the *** dynamic deformation data were subsequently interpolated and embedded into the CFD solver to account for the aeroelastic *** dynamic deformation data were further used to calculate the inertial forces by regarding the wing as a system of particles to take into account the wing *** temporal variation of the forces produced by the flapping wing was measured by a miniature load *** numerical results provide more flow details of the unsteady aerodynamics of the flapping wing in terms of vortex formation and *** calculated results of the inertial forces are analyzed and compared with the CFD results which represent the aerodynamic *** addition,the total forces,i.e.,the sum of the CFD result and inertial result,are compared with the experimental results,and an overall good agreement is obtained.

关键词： Aerodynamic force CFD Digital image correlation Flapping-wing micro air vehicles inertial force

Laminar Flow in the Gap between Two Rotating Parallel Frictional Plates in Hydro-viscous Drive

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Chinese Journal of Mechanical Engineering 2012年第1期25卷 144-152页

作者： HUANG Jiahai WEI Jianhua QIU Minxiu The State Key Lab of Fluid Power Transmission and Control Zhejiang UniversityHangzhou 310027China

The velocity, pressure and temperature distributions of the flow in the gap between hydro-viscous drive friction disks are the key parameters in the design of hydro-viscous drive and angular velocity controller. In the previous works dealing with the flow in the gap between disks in hydro-viscous drive, few authors considered the effect of Coriolis force on the flow. The object of this work is to investigate the flow with consideration of the effects of centrifugal force, Coriolis force and variable viscosity. A simplified mathematical model based on steady and laminar flow is presented. An approximate solution to the simplified mathematical model is obtained by using the iteration method assuming that the fluid viscosity remains constant. Then the model considering the effect of variable viscosity is solved by means of computational fluid dynamics code FLUENT. Numerical results of the flow are obtained. It is found that radial velocity profile diverges from the ideal parabolic curve due to inertial forces and tangential velocity profile is nonlinear due to Coriolis force, and pressure has two possible solution branches. In addition, it is found that variable viscosity plays an important role on pressure profiles which are significantly different from those of fluid with constant viscosity. The experimental device designed for this work consists of two disks, and one of them is fixed. Experimental pressure and temperature of the flow within test rig are obtained. It is shown that the trend of numerical results is in agreement with that of experimental ones. The research provides a theoretical foundation for hydro-viscous drive design.

关键词： hydro-viscous drive rotating disks flow inertial force viscosity-temperature characteristics

MODAL TEST AND ANALYSIS OF CANTILEVER BEAM WITH TIP MASS

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Acta Mechanica Sinica 2002年第4期18卷 407-413页

作者：肖世富杜强陈滨刘才山向荣山周为华徐友钜徐有刚 Southwest Institute of Structural Mechanics P.O.Box 919-401Mianyang 621900China Department of Mechanics & Engineering Science Peking UniversityBeijing 100871China

The phenomenon of dynamic stiffening is a research field of general interest for flexible multi-body *** fact,there are not only dynamic stiffening but also dynamic softening phenomenon in the flexible multi-body *** this paper,a non-linear dynamic model and its linearization characteristic equations of a cantilever beam with tip mass in the centrifugal field are established by adopting the general Hamilton Variational ***,the problems of the dynamic stiffening and the dynamic softening are studied by using numerical ***, the modal test is carried out on our *** numerical results show that the system stiffness will be strengthened when the centrifugal tension force acts on the beam (*** dynamic stiffening).However,the system stiffness will be weakened when the centrifugal compression force acts on the beam (*** dynamic softening). Furthermore,the equilibrium position of the system will lose its stability when the inertial force reaches a critical *** theoretical analysis,we find that this phenomenon comes from the effect of dynamic softening resulting from the centrifugal compression *** test results verify the above conclusions and confirm that both dynamic stiffening and softening phenomena exist in flexible multi-body systems.

关键词： flexible multibody system centrifugal field inertial force dynamic stiffening dynamic softening

LABORATORY STUDIES ON WAVE force OF COASTAL STRUCTURES MADE OF FLAT GEOTUBES

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Journal of Hydrodynamics 2011年第6期23卷 820-825页

作者： LIN Gang SHU Yi-ming LU Xin DAI Lin-jun YU Xin-zhou ZHANG Xian-lei YI Jing-rong College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 China

Flat geotubes are widely used for coastal structures such as seawalls, breakwaters and sightseeing groins, etc.. However, the understanding of the stable mechanism involved in the wave-structure interactions should be deepened, and one of the important work is to clarify the stress state of the structure under the wave action. In this article, wave force acting on coastal structures made of flat geotube is experimentally investigated. The required drag, inertia and lift coefficients are especially analyzed from the results of hydraulic model experiments specially designed for geotube structure. Several types of structures made of flat geotubes under wave action have been tested in order to understand the stress state of the geotube fixed to force transducer within different structures. Experimental results show that the wave-induced forces on the instrumented geotube are markedly influenced by wave elements. Meanwhile, the magnitude of horizontal force of adjoining geotube is different at the same time.

关键词： flat geotube wave force coefficients inertial force drag lift coastal structure hydraulic model experiment

Dynamic Analysis and Structural Optimization of a Novel Palletizing Robot

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Journal of Beijing Institute of Technology 2010年第3期19卷 274-278页

作者：李金泉丁洪生段冰蕾南倩付铁 School of Automation Beijing University of Post and Telecommunication School of Mechanical Engineering Beijing Institute of Technology

A novel palletizing robot is presented and *** using the Newton-Euler method and the principle that the instantaneous inertial force system could be transformed into a static system,the force equilibrium equations of the whole robot and its subsystem were derived and the robot＇s dynamic models were *** that,an example simulation was performed by using Matlab software and the structural optimization of the robot＇s key parts were discussed and analyzed in ANSYS *** results show that the dynamic models are correct and can be helpful for the design,validation and kinetic control based on dynamics of this kind of palletizing robots.

关键词： Newton-Euler method palletizing robot inertial force dynamics structural optimization

The Nature of inertial and Vacuum Gravitational Field

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Journal of Modern Physics 2016年第15期7卷 2126-2134页

作者： Ning Wu Center for Theoretical Study Beijing China

The uniformly accelerated motion is studied in the framework of gauge theory of gravity. It is found that, when an inertial reference system is transformed into a uniformly accelerated system by a local gravitational gauge transformation, a non-trivial gravitational gauge field appears. If there is a mass point in the new reference frame, there will be a non-trivial gravitational force acting on it. The nature and the characteristic of this new force are completely the same as those of the traditional inertial force. This new gravitational force is considered to be the inertial force. Therefore, the nature of inertial force is gravity, which is the basic idea of the equi-valence principle.

关键词： Lorentz Transformation Gravitational Gauge Transformation inertial force Gauge Theory of Gravity Gravitational Gauge Field