Identifying the Design Alternatives and Flow Interference of Tuna Purse Seine by the Numerical Modelling Approach

Dynamic responses of tuna purse seine to currents were numerically studied with regard to the vertical subsidence and global load distribution, and determinant attributes were identified. We rebuilt the submerged geometry of a purse seine net using the lumped mass method with hydrodynamic coefficients obtained from measurements of the prototype material, as well as a mesh grouping method, which corrects the twine diameter and netting material density for the equivalent net by introducing the compensation coefficient. Uneven tension distribution showed that it was vulnerable to high loads in the bunt area at shooting and along the lead line at pursing. High loads were present at the convex sections of net circles in the direction of the current. Higher shooting speeds resulted in well-balanced sinking, while a reduced hanging ratio of netting panels was beneficial to faster sinking. While large mesh sizes reduce water resistance and increase sinking velocity, extensive use should be cautioned in terms of the sensibility to stress. Comparing two options of different proportions of large-mesh panels, mesh sizes doubled for 15 strips versus 5 strips, suggesting that the 15 strip option would pose a higher risk of strand vulnerability, while the 5 strip option may be a more balanced alternative with a lower mesh density and a lower mesh stress.

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Research on Vibration Influence Chart of Planetary Gear Systems

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.86.747 ◽

2011 ◽

Vol 86 ◽

pp. 747-751 ◽

Cited By ~ 1

Author(s):

Le Hao Chang ◽

Geng Liu ◽

Li Yan Wu ◽

Zhong Hong Bu

Keyword(s):

Planetary Gear ◽

Dynamic Responses ◽

Lumped Mass ◽

Mesh Stiffness ◽

Common Definition ◽

Lumped Mass Method ◽

The Common ◽

Gear Systems ◽

Planetary Gear System ◽

Definition Of

The common definition of vibration influence chart is proposed in this study. A 46 degree-of-freedom time-varying dynamic model with coupled translation-rotation effect is developed to simulate the vibration of an encased differential planetary gear system using lumped mass method. With the dynamic load and the acceleration on gears and bearings as references, the dynamic responses in different load cases are investigated to search the change law of concerned parameters. The parameters considered include mesh stiffness, structure stiffness, gear mass and moment of inertia. The good and poor regions for vibration are evidently presented in figures, which is convenient to conduct the parameters design of planetary gear systems.

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Dynamic analysis of a helical gear reduction by experimental and numerical methods

Noise Control Engineering Journal ◽

10.3397/1/37684 ◽

2020 ◽

Vol 68 (1) ◽

pp. 48-58

Author(s):

Chao Liu ◽

Zongde Fang ◽

Fang Guo ◽

Long Xiang ◽

Yabin Guan ◽

...

Keyword(s):

Numerical Methods ◽

Dynamic Analysis ◽

Dynamic Behavior ◽

Fourth Order ◽

Numerical Models ◽

Helical Gear ◽

Operating Conditions ◽

Dynamic Responses ◽

Lumped Mass ◽

Gear Mesh

Presented in this study is investigation of dynamic behavior of a helical gear reduction by experimental and numerical methods. A closed-loop test rig is designed to measure vibrations of the example system, and the basic principle as well as relevant signal processing method is introduced. A hybrid user-defined element model is established to predict relative vibration acceleration at the gear mesh in a direction normal to contact surfaces. The other two numerical models are also constructed by lumped mass method and contact FEM to compare with the previous model in terms of dynamic responses of the system. First, the experiment data demonstrate that the loaded transmission error calculated by LTCA method is generally acceptable and that the assumption ignoring the tooth backlash is valid under the conditions of large loads. Second, under the common operating conditions, the system vibrations obtained by the experimental and numerical methods primarily occur at the first fourth-order meshing frequencies and that the maximum vibration amplitude, for each method, appears on the fourth-order meshing frequency. Moreover, root-mean-square (RMS) value of the acceleration increases with the increasing loads. Finally, according to the comparison of the simulation results, the variation tendencies of the RMS value along with input rotational speed agree well and that the frequencies where the resonances occur keep coincident generally. With summaries of merit and demerit, application of each numerical method is suggested for dynamic analysis of cylindrical gear system, which aids designers for desirable dynamic behavior of the system and better solutions to engineering problems.

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A Simplified Model of SSI Dynamic Analysis

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.446-449.334 ◽

2012 ◽

Vol 446-449 ◽

pp. 334-339

Author(s):

Zhi Ying Zhang ◽

Ying Li ◽

Qing Sun

Keyword(s):

Dynamic Analysis ◽

Soil Structure ◽

Design Method ◽

Simplified Model ◽

Lumped Mass ◽

Foundation Soil ◽

Linear Elastic ◽

Lumped Mass Method ◽

Actual Mechanism ◽

Seismic Design Method

Aiming at the problem of dynamic analysis of SSI system, the dynamic influence of different parts of foundation soil is studied on the linear elastic assumption according to the actual mechanism of Soil-Structure Interaction (SSI); in addition, a simplified model on the condition of the lumped mass method is put forward and the corresponding motion equations of SSI system are built, which can be a reference for the structural seismic design method considering SSI effect.

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Modeling and Simulation of Clamp Band Dynamic Envelope in a LV/SC Separation System

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.141.359 ◽

2011 ◽

Vol 141 ◽

pp. 359-363 ◽

Cited By ~ 5

Author(s):

Jun Lan Li ◽

Shao Ze Yan ◽

Xue Feng Tan

Keyword(s):

Friction Coefficient ◽

Modeling And Simulation ◽

Band System ◽

Separation Process ◽

Impact Behavior ◽

Separation System ◽

Lumped Mass ◽

Lumped Mass Method ◽

Simulation Results ◽

Contact Impact

The clamp band system is a typical locked and separated device of the launch vehicle (LV) / the spacecraft (SC), and its release-separation process is one of the important factors that affect the LV/SC separation movement. A nonlinear spring-damper model was employed to describe the contact-impact behavior between the V-segment of the clamp band and the LV/SC interface, and lumped mass method was used to depict the clamp band. By using ADAMS, a dynamic model of the clamp band system was established. The simulation results show that the impulse of the explosive bolts and the stiffness of lateral-restraining springs have significant effects on the clamp band dynamic envelope. The shock of the satellite-vehicle separation is very vulnerable to the clamp band pretension and the friction coefficient between the V-segment and the LV/SC interface.

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Research on Dynamic Simulation of AUV Launching a Towed Navigation Buoyage

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.433-435.1170 ◽

2013 ◽

Vol 433-435 ◽

pp. 1170-1174

Author(s):

Guang Pan ◽

Zhi Dong Yang ◽

Xiao Xu Du

Keyword(s):

Angular Momentum ◽

Boundary Conditions ◽

Dynamic Simulation ◽

Numerical Scheme ◽

Mathematic Model ◽

Dynamic Equations ◽

Lumped Mass ◽

Lumped Mass Method ◽

Towed Cable ◽

Undersea Vehicle

A mathematic model was established to simulate the process of AUV (autonomous undersea vehicle) launching a towed buoyage. Based on the lumped mass method and moment theorem and angular momentum theorem, dynamic equations of the cable and the buoyage were developed, respectively. Then the boundary conditions and the numerical scheme to deal with the cable with non-fixed length were presented. Moreover, the process of AUV launching a towed cable was simulated. By using the model, the results show the trajectory of buoyage and shape of towed cable can be well predicted.

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Numerical Simulation of Subsea Cluster Manifold Installation by the Sheave Method

Volume 5: Pipelines, Risers, and Subsea Systems ◽

10.1115/omae2018-77336 ◽

2018 ◽

Author(s):

Yu Zhao ◽

Yingying Wang ◽

Liwei Li ◽

Chao Yang ◽

Yang Du ◽

...

Keyword(s):

Numerical Simulation ◽

Mathematical Model ◽

South China Sea ◽

Deep Sea ◽

High Reliability ◽

Two Dimensional ◽

Complex Environment ◽

Lumped Mass ◽

Lumped Mass Method ◽

The Mathematical Model

The sheave installation method (SIM) is an effective and non-conventional method to solve the installation of subsea equipment in deep water (>1000m), which has been developed to deploy the 175t Roncador Manifold I into 1,885 meters water depth in 2002. With the weight increment of subsea cluster manifold, how to solve its installation with the high reliability in the deep sea is still a great challenge. In this paper, the installation of the 300t subsea cluster manifold using the SIM is studied in the two-dimensional coordinate system. The mathematical model is established and the lumped mass method is used to calculate the hydrodynamic forces of the wireropes. Taking into account the complex environment loads, the numerical simulation of the lowering process is carried out by OrcaFlex. The displacement and vibration of the subsea cluster manifold in the z-axis direction and the effective tension at the top of the wireropes can be gotten, which can provide guidance for the installation of the cluster manifold in the South China Sea.

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Modeling and Analysis of Amplitude-Frequency Characteristics of Torsional Vibration for Automotive Powertrain

Shock and Vibration ◽

10.1155/2020/6403413 ◽

2020 ◽

Vol 2020 ◽

pp. 1-17

Author(s):

Jinli Xu ◽

Jiwei Zhu ◽

Feifan Xia

Keyword(s):

Torsional Vibration ◽

Transmission Error ◽

Frequency Characteristics ◽

Response Analysis ◽

Lumped Mass ◽

Modeling And Analysis ◽

Gear Mesh ◽

Runge Kutta Method ◽

Lumped Mass Method ◽

Automotive Powertrain

In the present paper, the amplitude-frequency characteristics of torsional vibration are discussed theoretically and experimentally for automotive powertrain. A bending-torsional-lateral-rocking coupled dynamic model with time-dependent mesh stiffness, backlash, transmission error etc. is proposed by the lumped-mass method to analysis the amplitude-frequency characteristic of torsional vibration for practical purposes, and equations of motive are derived. The Runge–Kutta method is employed to conduct a sweep frequency response analysis numerically. Furthermore, a torsional experiment is performed and validates the feasibility of the theoretical model. As a result, some torsional characteristics of automotive powertrain are obtained. The first three-order nature torsional frequencies are predicted. Torsional behaviors only affect the vibration characteristics of a complete vehicle at low-speed condition and will be reinforced expectedly while increasing torque fluctuation. Gear mesh excitations have little effects on torsional responses for such components located before mesh point but a lot for ones behind it. In particular, it is noted that the torsional system has a stiffness-softening characteristic with respect to torque fluctuation.

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Numerical Modelling of the Mooring Line Failure Induced Performance Changes of a Marine Fish Cage in Irregular Waves and Currents

Volume 3: Structures, Safety, and Reliability ◽

10.1115/omae2019-95730 ◽

2019 ◽

Author(s):

Hung-Jie Tang ◽

Ray-Yeng Yang ◽

Chai-Cheng Huang

Keyword(s):

Marine Fish ◽

Low Frequency ◽

Frequency Region ◽

Irregular Waves ◽

Mooring Line ◽

Lumped Mass ◽

Lumped Mass Method ◽

Waves And Currents ◽

Failure Scenario ◽

The Time Domain

Abstract This study aims to investigate the performance changes resulted from a mooring line failure of a marine fish cage exposed to irregular waves and current. A numerical model based on the lumped mass method and Morison equation was extended to simulate the mooring line failure scenario. In this study, the failed resulting changes were compared with its normal counterpart in both the time domain and the frequency domain. After one upstream anchor loss, the maximum tension on the remaining anchor has increased significantly, as well as the drift distance of the rearing part (net chamber, floating collar, and tube-sinker) of the fish cage. The resulting changes can also be seen in both the wave-frequency and the low-frequency region in the spectra, including mooring tensions and body motions.

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Spectrally Consistent Approximations to the Matrix Exponent and Their Applications to Boundary Layer Problem

Computational Methods in Applied Mathematics ◽

10.2478/cmam-2002-0020 ◽

2002 ◽

Vol 2 (4) ◽

pp. 354-377

Author(s):

Vladimir V. Bobkov

Keyword(s):

Piecewise Linear ◽

Parabolic Problems ◽

Resolvent Estimate ◽

Weighted Norm ◽

Lumped Mass ◽

Boundary Layer Problem ◽

Lumped Mass Method ◽

The Matrix ◽

Mesh Ratio ◽

Ratio Condition

AbstractIn an attempt to show maximum-norm stability and smoothing estimates for finite element discretizations of parabolic problems on nonquasi-uniform triangulations we consider the lumped mass method with piecewise linear finite elements in one and two space dimensions. By an energy argument we derive resolvent estimate for the associated discrete Laplacian, which is then a finite difference operator on an irregular mesh, which show that this generates an analytic semigroup in l_p for p‹∞ uniformly in the mesh, assuming in the two-dimensional case that the triangulations are of Delaunay type, and with a logarithmic bound for p=∞. By a different argument based on a weighted norm estimate for a discrete Green's function this is improved to hold without a logarithmic factor for p=∞ in one dimension under a weak mesh-ratio condition. Our estimates are applied to show stability also for time stepping methods.

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