Table of Content

29 March 2017, Volume 51 Issue 3 Previous Issue    Next Issue

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Indoor Air Quality Affected by Ultrasonic Atomization Liquid#br#  Desiccant Dehumidification System LI Xi,ZHANG Kaisheng,YANG Zili,LIAN Zhiwei 2017, 51 (3):  257.  Abstract ( 818 )   Save Abstract： The effect of ultrasonic atomization liquid desiccant dehumidification system (UADS) on indoor air quality was studied in this paper. The safety threshold of lithium chloride in indoor air was proposed to be 70μg/m3. Besides, the influence of inlet mass fraction of LiCl (wi) and mesh mist eliminator porosity on carryover was experimentally studied and analyzed. Results show that when the wi rises from 31.5% to 38.8%, the carryover increases to 26.93μg/m3. In addition, the porosity of mesh mist eliminator affects carryover significantly, porosity lower than 93.5% is safe. However, carryover is lower than the safety threshold even under the most unfavorable condition, it manifests UADS cannot affect indoor air quality. The result of this study provides some practical information for application of UADS. References | Related Articles | Metrics

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Numerical Calculation of Added Resistance of Ships in#br#  Waves Based on Weakly Nonlinear Assumption CHEN Si,MA Ning,GU Xiechong 2017, 51 (3):  277.  Abstract ( 944 )   Save Abstract： The added resistance of ships in head waves is calculated under the assumption of weak nonlinearity in potential theory of ship motions. Maruo’s added resistance theory and the nonlinear ship motion theory are combined. The nonlinear ship motions are calculated using a time domain strip method, in which the FroudeKrylov force and hydrostatic force are nonlinear while the radiation force and diffraction force are still linear. Then the added resistance is obtained according to Maruo’s formula using the motion results. The computational results for S175 containership are used to validate the accuracy of the implemented methods and the results prove that the influence of wave steepness can be considered effectively. The influence of ship speed on the nonlinearity of added resistance is further investigated. References | Related Articles | Metrics

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Simulation of Liquid Tank Sloshing by#br#  Using Inhomogeneous Multiphase Model LIU Dongxi1,TANG Wenyong1,WANG Jin1,2,XUE Hongxiang1 2017, 51 (3):  283.  Abstract ( 919 )   Save Abstract： Three rollinduced sloshing cases involving two filling levels and two excitation frequencies are simulated by using the inhomogeneous multiphase model. The lateral and vertical movements of liquid gravity center are analyzed. The free surface profiles, velocity amplitude distribution, the time history of impact pressures and corresponding power spectrums are calculated by the presented approach. The excellent capability of the multiphase model for sloshing simulation is validated by the qualitative and quantitative comparisons of experimental and numerical results obtained by inhomogeneous and homogeneous multiphase models, respectively. References | Related Articles | Metrics

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Maneuverability of a New Concept Unmanned Shuttle Vessel WANG Jiana,LIU Jingyanga,b，WEI Chengzhua,YI Honga,b 2017, 51 (3):  288.  Abstract ( 945 )   Save Abstract： A new concept unmanned surface vehicle (USV) i.e. shuttle vessel with semiplaning wavepiercing feature is introduced, and its excellent maneuverability is studied. According to the International Maritime Organization (IMO) standards for ship manoeuvrability, the system of the freerunning shuttle vessel model is built to do some standard freerunning model maneuverability tests and to obtain the related data. The maneuverability of the shuttle vessel is studied and analyzed according to the ship maneuverability theory combined with the experimental data. The results demonstrate that the shuttle vessel has good maneuverability and flexibility, and it has its own unique maneuverability characteristics and advantages. Some analyses of its unique characteristics are done by numerical computation method. References | Related Articles | Metrics

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Numerical Study of Pressure Fluctuation for Bow Thruster LIU Hui1,2,FENG Yukun1,2,CHEN Zuogang1,2,3,DAI Yi1,2,3,TIAN Ximin1,4 2017, 51 (3):  294.  Abstract ( 977 )   Save Abstract： A bow thruster is the main research object. In order to obtain the initial data for the optimization of structural design, the flow field in the tunnel is numerically simulated through solving the unsteady Reynoldsaveraged NavierStokes (RANS) equations by the finite volume method and the analysis on the pressure fluctuation is carried out. The numerical results agree very well with the measured data of the model test. The pressure fluctuation is concentrated in small area near the blade tip. By comparing the pressure fluctuation on the tunnel wall under different flow directions, it is found that the pressure fluctuation reaches the minimum and maximum value respectively when the flow is coming from the front and the back of the ship. Furthermore, the study shows that the fluctuating pressure is related to the complexity of the flow field. The smoother the flow is, the smaller the fluctuating pressure becomes, and vice versa. Due to the high precision of the numerical simulation, the results obtained in the paper are of great reference value for optimal design of structures. Therefore, the study is of profound practical significance in engineering. References | Related Articles | Metrics

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Effect of Partial Failure of SelfSupporting Prismatic Type B#br#  Liquefied Natural Gas Carriers’ Thermal Insulation Layer on#br#  Structure Safety MA Chenzeng,TANG Wenyong 2017, 51 (3):  300.  Abstract ( 879 )   Save Abstract： According to the selfsupporting prismatic type B (SPB) liquefied natural gas (LNG) carriers’ heat transfer characteristics after the failure of thermal insulation layer, the coefficients of area and temperature are proposed to describe the coupling between structure temperature field and air temperature field of internal convection space. A typical partial failure model is chosen to calculate the structure temperature field and thermal stress by computational fluid dynamics (CFD) numerical simulation and finite element method, and the change of temperature and stree before and after the partial failure is analyzed to estimate the effect of the thermal insulation layer failure on the structure safety. The results provide a reference for the research on the structure safety of SPB LNG carrier. References | Related Articles | Metrics

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Advanced Grade Evaluation of Trailing Suction Hopper Dredger WANG Yunlong，LI Kai，SHEN Jiaqi，JIN Chaoguang，CHEN Xiaoya 2017, 51 (3):  305.  Abstract ( 1062 )   Save Abstract： Combined with the characteristics of trailing suction hopper dredger (TSHD), the advanced grade evaluation method for TSHD which has been delivered is proposed on the basis of the national standard. The evaluation criteria system and calculation method are put forward to assess the capability of TSHD. Results of analysis and calculation examples prove the availability of evaluation criteria system and calculation method for TSHD. The advanced level of TSHD in the same type ship can be graded according to the obtained evaluation results to appraise whether the TSHD achieves the desired results, find out the existing problems, and summarize the experience to guide the future work. At the same time, the evaluation criteria system and calculation method will be a beneficial complement to function grade valuation system of ships and ocean structures in the national standard. References | Related Articles | Metrics

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Collaborative Optimization for Composite Material Pressure Hull#br# Based on Lamination Parameters LI Bina,PANG Yongjiea,CHENG Yanxuea,ZHU Xiaomengb 2017, 51 (3):  308.  Abstract ( 1028 )   Save Abstract： Given that the material performances are certain, the layout optimization is accomplished, where the fiber volume fraction and ply thickness are taken as design variables and the objective is the minimum structural mass. The lamination parameters are introduced as optimization variables to achieve structural layup optimization with the structural stability and material strength taken into consideration. The structure/material collaborative optimization of composite material pressure hull is performed by integrating optimization results of each subsystem. The results show that the mass of the pressure hull decreases by 20.57%, the critical buckling pressure is 30.78 MPa, the failure index is 0.675. The desired results are achieved. The presented collaborative optimization method based on lamination parameters can optimize the composite material pressure hull with high accuracy and solve problem of low efficiency of optimization with ply angle directly set as design variables. References | Related Articles | Metrics

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Design and Numerical Analysis of Hydrodynamic Performance for #br# AntiCavitation Twisted Rudder YE Jinming,WANG Wei,YU Anbin,ZHANG Kaiqi 2017, 51 (3):  314.  Abstract ( 1050 )   Save Abstract： The propeller wake is calculated by a surface panel method, and then the attack angle of the twisted rudder can be designed through the propeller wake. An approach of anticavitation twisted rudder is proposed. The hydrodynamic performance of rudder after propeller is calculated by a computational fluid dynamics (CFD) method, and it is validated by the rudder force tests. The pressure distributions of the twisted and ordinary rudders are compared with each other. The peak of negative pressure on the twisted rudder is smaller than that of the ordinary rudder. The twisted rudder has a better anticavitation performance and can reduce cavitation erosion，vibration and noise. Because the twisted rudder has better match performance for the propeller wake than the ordinary rudder, it has  lower cross force and torque than the ordinary rudder when the rudder angle is zero. The fact is favorable to rudder and steering engine. References | Related Articles | Metrics

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Influence of AngleVariable Stern Flap on#br#  Resistance Performance of Stepped Planing Hull JIANG Yi,SUN Hanbing,ZOU Jing,YANG Dongmei,HU Ankang 2017, 51 (3):  320.  Abstract ( 1059 )   Save Abstract： In order to study the effects of the mounting angle of stern flap on the resistance performance of stepped planing hull, we carried out a series of model tests for a doublestepped planing hull with flap mounting angle β=2°, 3°, 4.5°. A finite volume method (FVM) based computational fluid dynamics (CFD) software CFX was used to simulate the flow field around the tested models at the volume based Froude numbers ranging from 0.44 to 5.20. The operating mechanism of the flap and the effects of mounting angle on the hydrodynamic characteristics were analyzed. Comparisons of air cavities after steps and load coefficient of planing surfaces between different models were presented and discussed. The experimental and numerical results showed that increasing the mounting angle could improve the lowspeed resistance performance and increase the critical velocity at which porpoising would happen, whereas only less resistance increase could be observed at high speed. References | Related Articles | Metrics

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Numerical Analysis of Impeller Flow Field of#br#  Waterjet SelfPropelled Ship Model GONG jie,GUO Chunyu,ZHANG Haipeng 2017, 51 (3):  326.  Abstract ( 891 )   Save Abstract： The virtual disk (VD) and overset (OS) models had been applied to the numerical simulation of impeller in waterjet which was installed on ship model in order to build numerical model for selfpropulsion test. Research and discussions were mainly concentrated on the axial velocity distribution of hull flow field and internal flow field, and the flow field characteristics of waterjet propelled ship were analyzed. The results revealed that the hull flow field coincided with each other for two models, but there was obvious difference in the internal flow field. Compared with the VD model, the OS model is more applicable to the actual state of the impeller. Both calculating models simulated the flow field characteristics of waterjet propelled ship well. There was significant consistency both in the regularities of local pressure distribution and wave jamming effect caused by jet steam. References | Related Articles | Metrics

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Fatigue Analysis of TransverseOscillation of#br#  Soft Yoke Mooring System Based on Field Monitoring FAN Zheliang1,WANG Yanlin1,YUE Qianjin1,SUN Ye2 2017, 51 (3):  332.  Abstract ( 1013 )   Save Abstract： The resonance phenomenon of soft yoke mooring system (SYMS) transverseoscillation and tanker rolling was analyzed by the method of phase analysis to solve the problem of transverseoscillation in the SYMS of floating production storage and offloading (FPSO). Fatigue analysis method of the SRA transverseoscillation was studied. The upper hinge point of the SYMS was taken as an example. The number of cycles of upper hinge point in oneyear was counted by rain flow counting method, and the number of cycles in 15 years could be calculated. Therefore, the fatigue damage under the cycles of 15 years could be calculated by finite element analysis. The results show that the fatigue damage is up to 0.57. There exists a risk of fatigue failure in design life. It is urgent to find a practical and reliable method to reduce the impact of resonance. References | Related Articles | Metrics

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Ship Block Transportation Scheduling Approach Based on#br#  Genetic Algorithm WANG Chong1,MAO Yunsheng1,SHIN Jonggye2 2017, 51 (3):  338.  Abstract ( 1017 )   Save Abstract： This paper presented a twostage optimization model defined as the minimum number of transporters and task completion time of ship block transportation to efficiently solve the block transportation scheduling in the shipyard. Two kinds of heuristic method based on genetic algorithm were proposed. The numerical experiment method was used to validate the model, and the results showed that the two proposed algorithms realized the efficient use of the transporters in shipyard. References | Related Articles | Metrics

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Analysis of Elastic Parameters for Laminated Fabrics Used in#br#  Airships Under Biaxial Stresses CHEN Jianwen1,ZHOU Han1,CHEN Wujun2,ZHAO Bing2,WANG Mingyang3 2017, 51 (3):  344.  Abstract ( 671 )   Save Abstract： In order to reveal the response characteristics of elastic parameters for laminated fabric used in airships under biaxial stress loading, a series of biaxial tensile tests were first conducted on high performance envelope materials Uretek3216LV. The stressstrain data of nine stress ratios were obtained, and their nonlinear and orthotropic behaviors were analyzed. According to the testing method for elastic constants of membrane materials, the elastic parameters of the studied material were then calculated and the effects of the stress ratio and stress ratio combination on theses parameters were discussed. Finally, using the Matlab program, the response characteristics of elastic parameters in plane stress space were obtained and analyzed, and a weighting method was proposed to calculate the elastic parameters and to achieve the influences of the stress levels and stress ratios. Results indicate that there is no coupling relation between these parameters, and then the reciprocal relationship may not apply to constitutive model of laminated fabrics. The mechanical behaviors of the studied material are affected by the stress ratios and stress ratio combinations significantly, and obvious linearity and orthotropy can be observed for different stress levels and stress ratios. Therefore, during the real design practice of airship structures, for a steady reliable calculation of elastic parameters it might be more seasonable to use determination options whose stress ratios are determined by specific stress distributions of structural member. References | Related Articles | Metrics

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Analytical Calculation of the Optimal Damping Ratio of#br#  Secondary VerticalSuspension System for Subway ZHOU Changcheng1,YU Yuewei1,ZHAO Leilei1,2 2017, 51 (3):  353.  Abstract ( 1204 )   Save Abstract： For the problem of damping matching of subway secondary verticalsuspension system, an analytical calculation method of optimal damping ratio was provided. Based on the analysis of the typical track spectra, the track verticalprofile irregularity model built by the curve fitting method was established to effectively reflect the actual track traffic conditions and meet the theoretical analysis of vehicle running stability. According to the 1/4 vehicle threedegreeoffreedom verticalvibration model, the analytical calculation model of subway secondary verticalsuspension optimal damping ratio was built by the theory of random vibration and residue theorem. The model was aimed at minimum of mean square value of the vibration acceleration and was validated by the example calculation and simulation results. The maximum relative deviation of damping ratio between the analytical calculation value and the simulation value is only 2.55%. It shows that the analytical calculation model of subway secondary verticalsuspension optimal damping ratio is correct. References | Related Articles | Metrics

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Effect of Girder Vertical Deformation of Simply Supported Beam#br#  Bridges on the Running Properties of DoubleLane LightRail Train WANG Shaojie1,3,XU Zhaodong1,LIU Fusheng2,LI Shu1,DYKE S J3 2017, 51 (3):  359.  Abstract ( 691 )   Save Abstract： Based on the modeling theory of lightrail traintrackbridge (LTTB) system, a finite element (FE) model with consideration of girder deformation is established to perform analysis on dynamic behaviors of the multiple span girder bridge in the case of the doublelane trains passing through it. Factors such as nonlinearity of subsystem, wheeltruck contact and rail irregularities are also considered in this FE model. This model has unique merits of dynamic visual, high efficiency and rubust solutions. The offload factor, maximum acceleration of car body and Sperling index are employed to evaluate the performance of the running lightrail train. Besides, the interaction of running trains and girder deformation is investigated in detail. The results show that first, the running safety and stability of the train degenerate as the speed goes up. Then, the girder deformation leads to varying impacts on the running safety and stability of the train at the same train speed. For the case of the existing girder deformation, the running performance of the train is dominated by the factor of offload. Finally, when the train runs at not greater than 80km/h of  the design speed, it can meet the requirements of running safety while the pier settlement is not more than 30mm or the deflection/camber of girder is not more than 20 mm. References | Related Articles | Metrics

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Effect of Icing on Airfoil with Control Surface and Analysis of#br# Aerodynamic Parameters LI Dong,ZHANG Chen,WANG Fuxin,LIU Hong 2017, 51 (3):  367.  Abstract ( 811 )   Save Abstract： The aerodynamic character of an icedairfoil is closely related to the ice conformation, the effect of ice conformation on the flow field and the associated aerodynamic parameters of the elevator are unknown. In the present study, computational fluid dynamics (CFD) calculation was performed to simulate the flow features around an iced airfoil with control surface. Quantitative analyses were conducted to reveal the relations between the lift coefficient and the elevator deflection under various angles of attack. Comparison of the change rates of the lift coefficient with respect to the deflection angle was also given between the conditions of horn ice and ridged ice. The result indicate that related to a clean airfoil, the lift coefficient and its rate of change of an iced airfoil are severely degraded. The up wash effect induced by the downward deflection of the elevator aggravates the disturbance of the flow field caused by horn ice. In comparison with horn ice, flow over ridged ice separates more extensively in the upper surface of the tail, resulting in a smaller stall angle and a severe degradation of the derivative of lift coefficient to the deflection of the elevator. A threestep plunge of the relative aerodynamic derivative ratio is found to be a consequence of the increase of angle of attack and the elevator deflection for a hornice airfoil, while a twostep plunge with greater declination rates is observed for a ridgedice airfoil. References | Related Articles | Metrics

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Scaling Effects of Hydrofoil Tip Vortex Cavitation Inception PU Jijun,XIONG Ying,WANG Rui 2017, 51 (3):  374.  Abstract ( 832 )   Save Abstract： LES model was conducted in the analysis of hydrofoil tip vortex flow field．In order to reduce the discrete error induced by the grid, mesh refinement was applied to the area of the tip vortex core in numerical simulation. The axis velocity and tangential velocity of the tip vortex flow field with no cavitation were calculated and the results are in good agreement with experiments. The scaling law of tip vortex cavitation inception number is introduced and has been modified with the data of vortex core radius and vortex strength. References | Related Articles | Metrics

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Strategies Design for Online Newsboy Model with #br# Defect Rate and Delay Payment KANG Wanglin,WANG Lei,ZHANG Bo 2017, 51 (3):  379.  Abstract ( 798 )   Save Abstract： The online newsboy problem with defect rate and delay payment  is studied. Some online ordering strategies for the existence of defect rate and delay payment are presented by using the competitive analysis theory to problem with different risk preference. The results show that these strategies are useful, and the defect rate threshold and delay payments can help the newsboys to make online decision about ordering strategies with the incomplete information. The delay payments make the online newsboys to be risktaking and afford the higher defect rate. At the same time, this kind of delay payments also can help the suppliers to improve the technology and decrease the defect rate. References | Related Articles | Metrics