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Table of Content

    28 December 2019, Volume 53 Issue 12 Previous Issue    Next Issue
    Test on Maneuverability in the Vertical Plane of a Revolution Submersible at Large Attack Angle in Circulating Water Channel
    LIANG Xiaoyang,MA Ning,LIU Han,GU Xiechong
    2019, 53 (12):  1395-1403.  doi: 10.16183/j.cnki.jsjtu.2019.12.001
    Abstract ( 1020 )   PDF (3008KB) ( 393 )   Save
    A series of static tests on a 1/2 scaled standard fully appended SUBOFF model are carried out by the planar motion mechanism(PMM) in the circulating water channel (CWC),by which the maneuverability in the vertical plane is studied including the uncertainty analysis. The horizontal force, the vertical force and the trim moment of the submersible model are measured under several angles of attack (ranging from -60° to 60°) and flow rates (ranging from 10m/s to 12m/s). The mathematical model of maneuverability motion in the vertical plane of the submersible is derived by piecewise function based on the results. The dimensionless hydrodynamic coefficients in the motion equation are analyzed with the least-square method. The results show that the total uncertainty of the measured dimensionless hydrodynamic forces and moment is small to illustrate the validity of the testing method. The dimensionless values of the vertical forces and the trim moment increase with the angle of attack increasing. There are obviously asymmetric and nonlinear characteristics in the dimensionless hydrodynamic forces and moment as the angle of attack is beyond the range of -25° to 25°. Piecewise function is more applicable for describing maneuverability motion in the vertical plane of the submersible under large angle of attack.
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    Extreme Response Estimate of Jack-Up Platforms Under the Action of Random Wave Loads
    XU Chaochao,NI Ping,GU Ying,HE Jun
    2019, 53 (12):  1404-1410.  doi: 10.16183/j.cnki.jsjtu.2019.12.002
    Abstract ( 889 )   PDF (1109KB) ( 224 )   Save
    For estimating the extreme response of the jack-up platform, a parametric method under the action of random wave loads is developed. The method approximates the extreme distribution of the stochastic response of the platform by using the shifted generalized lognormal distribution model. The model parameters are estimated by two supporting points and their exceeding probability in the adjacent tail distribution such that the size of the needed samples is reduced significantly. The extreme response analysis of a real platform shows that the proposed method has enough high numerical accuracy and needs relatively few computational costs, which is suitable for the reliability and risk assessment of the jack up platform under the action of random wave loads.
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    Deliberative Trajectory Planning for Shipborne Autonomous Collision Avoidance System
    YANG Rongwu,XU Jinsong,WANG Xin
    2019, 53 (12):  1411-1419.  doi: 10.16183/j.cnki.jsjtu.2019.12.003
    Abstract ( 904 )   PDF (3646KB) ( 334 )   Save
    Based on rapidly-exploring random tree (RRT) algorithm, a deliberative trajectory planner DTP was developed to search for global trajectory between the adjacent waypoints of the long voyage. The static obstacle constraints, ship maneuvering constraints, and trajectory optimality requirements are satisfied simultaneously to ensure the feasibility, completeness and optimality in planning. Through simulations and on-water tests of a trimaran model, the proposed DTP method was demonstrated to be effective, superior and stable for the autonomous collision avoidance. The present work provides an important basis for subsequent research and future application.
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    The Analysis of Ultimate Strength of Stiffened Panels Exposed to Fire Under Temperature Increase Condition
    ZHANG Liming,LI Yuanyuan,XUE Hongxiang,TANG Wenyong
    2019, 53 (12):  1420-1427.  doi: 10.16183/j.cnki.jsjtu.2019.12.004
    Abstract ( 811 )   PDF (7703KB) ( 809 )   Save
    Considering the thermodynamic properties of materials at different temperatures, the method of thermal-elastic-plastic finite element analysis and riks method are used to study the collapse mode and residual ultimate strength of stiffened panel exposed to fire. The residual ultimate strength of the uniaxial compression at different heating-up time is also calculated. The numerical results show that:the whole structure heats up faster and fails earlier when stiffener heated, which is more dangerous. The collapse mode is beam-column type collapse when plate heated. And the collapse mode is a combine of overall collapse mode and local buckling mode of stiffener web when stiffener heated. The ultimate strength of plate heated stiffened panel reduces to 13% of that in normal temperature and the ultimate strength of stiffener heated stiffened panel reduces to 5% when the heating time reaches 140s.
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    Numerical Studies on Hydrodynamic Performance of a SWATH Ship with Inclined Struts
    MAO Lifu,LI Yinghui,YI Hong
    2019, 53 (12):  1428-1439.  doi: 10.16183/j.cnki.jsjtu.2019.12.005
    Abstract ( 778 )   PDF (7716KB) ( 302 )   Save
    An unconventional small water-plane area twin-hull (SWATH) ship with inclined struts was investigated by numerical methods. The seakeeping performance was studied firstly based on the three-dimensional potential flow theory with considering viscous damping. The results show that the SWATH ship with inclined struts demonstrates improved seakeeping performances by comparison with a vertical-strut SWATH ship and the Delft 372 catamaran. Fully considering the viscous condition, 3D numerical simulations based on the Reynolds-averaged Navier-Stokes (RANS) equation and overset mesh method are carried out both in calm water and head regular waves. As negative added resistance is observed in the computational results, it can be concluded that the inclined struts could make use of wave energy to give rise to a reduction of power required in waves.
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    Development and Validation of a Time-Domain Coupling Simulation Code for Floating Offshore Wind Turbines
    CHEN Jiahao,LIU Geliang,HU Zhiqiang
    2019, 53 (12):  1440-1449.  doi: 10.16183/j.cnki.jsjtu.2019.12.006
    Abstract ( 1105 )   PDF (1489KB) ( 361 )   Save
    The paper presents the theories of an in-house time-domain simulation code for floating offshore wind turbines. The unsteady blade-element-momentum method with correction methods is applied to calculate aerodynamic loads. Combination of the potential-flow theory and the Morison’s formula are used to calculate hydrodynamic loads. The quasi-static catenary mooring method is implemented to calculate restoring forces from mooring lines. Kane’s dynamic equations are used to establish dynamic governing equation for the system. The generator-torque controller and the full-span rotor-collective blade-pitch controller are used to regulate wind energy tracking. Subsequently, feasibility testing of the code is conducted by a series of code-to-code comparisons, which will benefit researchers in their theoretical study and development of numerical code for floating offshore wind turbines.
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    Unsteady Flow Filed Study of Vaneless Diffuser in a Centrifugal Compressor Using Proper Orthogonal Decomposition Method
    YANG Xiaojian,HU Chenxing,ZHU Xiaocheng,DU Zhaohui
    2019, 53 (12):  1450-1458.  doi: 10.16183/j.cnki.jsjtu.2019.12.007
    Abstract ( 867 )   PDF (4713KB) ( 405 )   Save
    To investigate the unstable flow characteristics inside the centrifugal compressor with a vaneless diffuser, the proper orthogonal decomposition (POD) method was applied to the unsteady numerical simulation results to analyze the unsteady flow inside the vaneless diffuser under small flow conditions. The results indicate that the fluid field of vaneless diffuser is mainly influenced by the upstream blades and the downstream volute. In addition, POD method is capable of capturing the jet-wake flow structure, of which the characteristic frequency equals the blade passing frequency, as well as the unstable mode with low frequency. The characteristic frequency of the unstable mode is 22104Hz, and there exists several perturbations in different circumferential positions. These perturbations are mainly radial fluctuation but do not propagate in the circumferential direction. The reconstruction result of the unstable mode can visually show the development of the corresponding unstable flow. The sampling frequency of the flow field snapshots has an effect on the result of POD method.
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    Numerical Investigation of Flow and Heat Transfer of Ice Slurry Based on Population Balance Model
    ZOU Liangxu,MA Fei,MENG Zhaonan,ZHANG Peng
    2019, 53 (12):  1459-1465.  doi: 10.16183/j.cnki.jsjtu.2019.12.008
    Abstract ( 980 )   PDF (1682KB) ( 270 )   Save
    As a solid-liquid two-phase fluid, ice slurry is widely used in cold storage and transport systems due to its high energy storage density, good fluidity and heat transfer performance. Most of the studies on the flow and heat transfer characteristics of ice slurry are based on uniform particle diameter. In the present study, the flow and heat transfer characteristics of ice slurry are numerically investigated in horizontal circular pipes based on the variation of particle diameter through the Euler-Euler two-phase flow model with population balance model (PBM), which considers the interaction between the solid and liquid phases as well as the aggregation, breakage and melting of particles. The results show that the ice particle diameter increases with the increase of solid volume fraction and flow rate. The particle diameter changes from 125μm to 139μm at solid volume fraction of 10% and inlet velocity of 10m/s under the isothermal flow condition. Whereas the particle diameter gradually decreases from the initial diameter to completely melting at wall heat flux of 50kW/m2. Increasing the heat flux leads to a faster decrease of particle diameter and the particle diameter distribution is different from that under the isothermal flow condition.
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    Design of New Rail Mounted Gantry with the Regenerative Kinematic Chain Method
    ZHANG Qing,CHEN Miao,SUN Feng,QIN Xianrong,SUN Yuantao
    2019, 53 (12):  1466-1474.  doi: 10.16183/j.cnki.jsjtu.2019.99.004
    Abstract ( 1070 )   PDF (3057KB) ( 244 )   Save
    This paper proposed a novel rail mounted three-wheel gantry to improve the structure of traditional rail mounted gantry with larger weight and higher height by the regenerative kinematic chain method. Firstly, 16 kinds of kinematic chains for three-wheel gantry were obtained by embryo graph vertex insertion method. Then according to the topological requirements of mechanism, three kinds of kinematic chains with at least two three-kinematic-pairs and one of these connects three two-kinematic-pairs was screened from above chains. Finally, the best chain was chosed based on the principle of equilibrium wheel load, a novel three-wheel gantry with balancing-linkage mechanism was obtained. The results show that compared with the traditional gantry in same specifications, the weight and design height were reduced in the prototype gantry with new topological graph. Additionally, the new topological graph could be further used in the four-wheel gantry.
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    Monitoring of Grinding Signals and Development of Wheel Wear Prediction Model
    GUO Weicheng,LI Beizhi,YANG Jianguo,ZHOU Qinzhi
    2019, 53 (12):  1475-1481.  doi: 10.16183/j.cnki.jsjtu.2019.12.010
    Abstract ( 909 )   PDF (1616KB) ( 353 )   Save
    Based on the issue that monitoring of wheel wear is difficult to be implemented directly during grinding process, a multi-feature optimization and fusion based random forest (MFOF-RF) algorithm was proposed to realize the accurate prediction of wheel wear. An experiment of cylindrical traverse grinding was performed and the power, acceleration and acoustic emission signals were collected and processed in order to extract a large amount of time-domain and frequency-domain signal features. Statistical criteria were used to adjust model parameters and choose best feature combination for the prediction of wheel wear. The results shown that the MFOF-RF model improved the prediction accuracy and diminished error more than 30% compared with the model with single feature.
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    Output Feedback Control of Electro-Hydraulic Servo Systems with Command Filter
    WANG Guangwen,YAO Jianyong
    2019, 53 (12):  1482-1487.  doi: 10.16183/j.cnki.jsjtu.2019.12.011
    Abstract ( 831 )   PDF (2102KB) ( 263 )   Save
    An output feedback control algorithm with command filtering is proposed to solve the problem of uncertain nonlinear and unmeasurable state in the nonmatching model of electro-hydraulic servo systems. Through the effective integration of the extended state observer and command filtering technique, the state and external disturbances of the system are estimated by the extended state observer, the unmeasurable and uncertain nonlinear state problems are solved, and simultaneously the active compensation for disturbances is implemented. In process of controller design, the ‘differential explosion’ problem in backstepping scheme is avoided by using the command filter. Based on the Lyapunov function, the stability of the designed controller is proved and all the signals are bounded. The experimental results verify the effectiveness of the designed controller.
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    Effect of Deposition Path on Residual Stresses of Laser Additive Manufacturing Structures
    ZHANG Yifu,ZHANG Hua,ZHU Zhengqiang,SU Zhanzhan
    2019, 53 (12):  1488-1494.  doi: 10.16183/j.cnki.jsjtu.2019.12.012
    Abstract ( 1045 )   PDF (6991KB) ( 292 )   Save
    H13 tool steel powder is used as a raw material to rapidly form thin-walled structures using laser metal deposition technology. The gas/metal powder flow computational fluid dynamics (CFD) model was developed using Fluent software to analyze the forced convection heat loss parameters. The heat flow constitutive equations of the deposition process are established, the metal deposition is simulated using the life-and-death element technology, and the 3D thermo-mechanical sequential coupled finite element simulation of the laser metal deposition is performed based on the APDL language. The effects of deposition paths on the thermal distribution and residual stress field distribution of thin-walled structures were analyzed. The results show that there is a local residual tensile stress exceeding the tensile strength of the workpiece in the corners of the straight wall structure, resulting in cracks. Unlike the one-way deposition path, the zig-zag deposition path induces different symbolic residual shear stresses in the subsequent deposition layer. The temperature gradient of the one-way deposition wall is relatively low, and the residual stress is slightly lower than the zig-zag deposition wall, but the quality of the formed structures is low. The residual stress calculation results are in agreement with the experimental measurements, and can provide operation references for the deposition of specific part geometry.
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    Construction and Performance Investigation of Variable Cross-Section Scroll Profiles Based on Frenet Frame
    HOU Caisheng,LIU Tao
    2019, 53 (12):  1495-1501.  doi: 10.16183/j.cnki.jsjtu.2019.12.013
    Abstract ( 863 )   PDF (1488KB) ( 351 )   Save
    In the profiles design of scroll compressor, aiming at the problem of low compression ratio and inadequate area utilization ratio of the orbiting and the fixed scroll in the traditional constant cross-section scroll profiles,a new type of variable cross-section scroll profiles was proposed. Scroll profiles composed of circle involutes and three-order curve were constructed piecewise by using the Frenet frame. The basic geometrical theory of the profile was established. Displacement volume, compression ratio,area utilization coefficient,axial gas force and tangential gas force were introduced to evaluate the performance of scroll profiles. The results show that the newly constructed variable cross-section scroll profiles have better geometric performance than traditional constant cross-section scroll profiles composed of the single circle involute, and the changing range of dynamic performance are small. The displacement volume, compression ratio and area utilization coefficient are improved by 8.80%, 10.57% and 8.84% respectively.
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    Analysis and Suppression of Rehabilitation Robotic Wheelchair Vibrations Under Random Road Excitations
    ZHAO Leilei,YU Yuewei,ZHOU Changcheng,YANG Fuxing
    2019, 53 (12):  1502-1507.  doi: 10.16183/j.cnki.jsjtu.2019.12.014
    Abstract ( 814 )   PDF (921KB) ( 203 )   Save
    To effectively suppress vibrations of rehabilitation robot wheelchair under random excitations, an optimization method for suppression parameters is proposed. Taking cushions and tires as the vibration isolation elements with stiffness and damping, a vertical vibration model of human-wheelchair is established. Taking random excitations of road irregularities as typical model input, formulae of the human acceleration frequency response and the root-mean-square (RMS) response are derived, and response coefficients are proposed. Moreover, influences of the cushion system damping ratio and the tire system damping ratio are revealed. Based on the coefficients, an analytical optimization model for the two ratios is established. The results show that relative deviations of the cushion optimal damping and the tire optimal damping are 0.3% and 0.6%, respectively. The proposed analytical optimization model has been tested with case study and numerical simulation.
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    Application of Profile Likelihood Ratio and CLs Method in Data Analysis of PandaX-II Dark Matter Experiment
    ABDUKERIM Abdusalam,CHEN Xun,IMINNIYAZ Hoernisa
    2019, 53 (12):  1508-1514.  doi: 10.16183/j.cnki.jsjtu.2019.12.015
    Abstract ( 1062 )   PDF (1963KB) ( 380 )   Save
    The profile likelihood ratio statistics is used in the leading dark matter direct detection experiments around the world to perform the statistical analysis on the data. The results recently published in PandaX-II experiment present several constraints on the cross sections of dark matter scattering off nucleon via profile likelihood ratio and CLs method. This article introduces profile likelihood ratio and CLs method in detail and discusses how to construct profile likelihood ratio with the data analysis of PandaX-II as an example. The upper limits of the inelastic scattering cross section between dark matter particle and nucleon are obtained with CLs method.
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