2018 Vol. 13, No. 2

Contens of CJSR 2018, Vol.13, No.2
Chinese Journal of Ship Research
2018, 13(2): .
Abstract:
[1] Influence of carrier corridor configuration on evacuation performance…LIU Boyun,ZHOU Xiaosong,YAN Shuyi(1) [2] Two-dimensional numerical simulation of NACA 0012 flapping foil hydrodynamics…LV Yuanbo,TIAN Xinliang,LI Xin,et al(7) [3] Numerical research on control of longitudinal motion of ship in waves by T-foil…SUN Yifang,JIANG Yichen,ZONG Zhi(16) [4] Numerical simulation of three-dimensional flow around a circular cylinder of finite length…WANG Xiaocong,GUI Hongbin,LIU Yang(27) [5] Simulation analysis of overpressure value for collective protection system of surface ship…CHEN Hongchao,SONG Kaohua,BAO Jian,et al(35) [6] Manned submersible working cabin layout design method under cabin function system constraints and ergonomic constraints…CHEN Dengkai,FAN Yu,ZHANG Shuai,et al(41) [7] Peridynamic model for submarine surfacing through ice…YE Liyu,WANG Chao,GUO Chunyu,et al(51) [8] Vibro-acoustic characteristics of typical periodically stiffened plate based on spatial harmonic expansion method…GAO Shuang,ZHU Xiang,LI Tianyun,et al(60) [9] Influence factors analysis of flow-induced vibration of elbow in piping system…KE Bing(70) [10] Analysis of free vibration characteristics of thin rectangular plate with typically-shaped central opening…ZHANG Jun,LI Tianyun,ZHU Xiang,et al(76) [11] Optimization of natural frequency of laminated composite rudder…WU Jiatong,SHI Min,REN Chunyu(84) [12] Test method of Poisson's ratio for low modulus elastomer…ZHOU Jun,MEI Zhiyuan,WANG Yongli,et al(91) [13] Clustering-based classification method of loading schemes of multi-span beams under multiple patch loading…ZHU Guangji,HE Yuansong,WAN Qi,et al(97) [14] Preliminary design of rim-electric driven propeller and effect factor analysis on cogging torque…YU Ping,ZHOU Junwei,ZHANG Guozheng(103) [15] Feasibility research for design of marine propellers and energy recovery turbines…LI Hang,YU Long(110) [16] Thermal dynamic calculation method and characteristic analysis of marine secondary circuit system under all operating conditions…CUI Jialin,YANG Zichun,ZHANG Lei(116) [17] Influence factor analysis on anti-whip restraint of ship's main steam pipeline based on LS-DYNA…XUE Meixin,YANG Pengju,ZHAO Cuina(123) [18] Longitudinal vibration model and analytic study of submarine propulsion shafting…XU Da,HAN Baohong,HE Wanheng,et al(129) [19] Precision measurement of ship's induced vertical magnetic signatures…GUO Chengbao,ZHOU Weichang(135) [20] Numerical simulation of transient electromagnetic response of aircraft to lightning strikes…LI Qianhua,CHEN Xi,LIU He'nan,et al(140)
Ship Design and Performance
Influence of carrier corridor configuration on evacuation performance
Boyun LIU, Xiaosong ZHOU, Shuyi YAN
2018, 13(2): 1-6. doi: 10.3969/j.issn.1673-3185.2018.02.001
Abstract:
  Objectives  The aircraft carrier escape and evacuation process is complex and difficult to quantify.  Methods  To solve this problem, this paper develops an intelligent multi-purpose intelligent agent (MUPI) evacuation behavior model and simulates the evacuation process of aircraft carrier Saratoga on EXODUS, and the simulation results are verified by grey relational analysis.  Results  The following conclusions are obtained:escape time increases with the decrease of exit width when the exit width is less than 1 m; the influence of exit width on escape time is relatively large; when the exit width is greater than 2 m, changing the exit width has less effect on escape time; increasing the exit width has a better effect on average escape time than increasing the number of exits; for the three indicators of walking distance, distance travelled and average time taken, stair width has a greater effect than gate width or number of lifeboats.  Conclusions  The research findings of this paper can provide references for the layout design of domestic aircraft carriers.
Two-dimensional numerical simulation of NACA 0012 flapping foil hydrodynamics
Yuanbo LV, Xinliang TIAN, Xin LI, Chunhui SONG
2018, 13(2): 7-15. doi: 10.3969/j.issn.1673-3185.2018.02.002
Abstract:
  Objectives  In order to study the impact of the hydrodynamic performance of foil in the design of a wave glider,   Methods  on account of the characteristics of the oscillating foil when the wave glider is heaving, and based on the Dynamic Fluid Body Interaction(DFBI) module in STAR-CCM+ with the SST k-ω turbulence model, the passive oscillating process of foil when it is forced to heave is simulated. The effects of limit angles, wave heights and frequencies on the thrust coefficient of NACA 0012 flapping foil are investigated.  Results  We find that the passive rotation method can effectively simulate foil oscillating process, and its thrust coefficient is about 30% smaller than the coefficient obtained by the active rotation method. Moreover, the maximum limit angle of a wave glider of around 20° gives a better hydrodynamic performance. The numerical simulation result indicate that the thrust coefficient increases with the increase of wave height and wave frequency in a certain region.  Conclusions  This can provide a reference for propulsive performance and hydrodynamic performance under different states of the sea.
Numerical research on control of longitudinal motion of ship in waves by T-foil
Yifang SUN, Yichen JIANG, Zhi ZONG
2018, 13(2): 16-26. doi: 10.3969/j.issn.1673-3185.2018.02.003
Abstract:
  Objectives  A T-foil with an active control system can provide higher lift force and improve the seakeeping of a ship. It is necessary to calculate the anti-vertical motion effect with the different control signals.  Methods  The motion responses of the Wigley model in different wavelengths among three different Froude numbers are obtained via the slender body theory, and the lift force model of a T-foil is established. The torque control is used to obtain the governing equation of the T-foil's swing angle by analyzing the control signal. On the basis of calculating the motion of the Wigley model, the vertical motions of a ship with a T-foil in different control signals are calculated in time domain, and the attenuation effect with the three different control signals is compared. Finally the multi-signals hybrid control is studied preliminarily.  Results  The results show that the T-foil with torque control can reduce 32.43% of the heave and 57.62% of the pitch angle response extremum, and can provide a reduction of more than 61.17% in bow acceleration at peak response compared with a ship without a T-foil and with a high Froude number. The anti-vertical motion effect in the condition of Fr=0.3 is more obvious when the lift moment is controlled by the pitch angle signal, and as the speed of the ship increases, using the control signal of pitch angular velocity can obtain a lower vertical motion response.  Conclusions  In practical application the swinging angle of the T-foil can be controlled by different signals and control parameters at different speeds.
Numerical Simulation of three-dimensional flow around a circular cylinder of finite length
Xiaocong WANG, Hongbin GUI, Yang LIU
2018, 13(2): 27-34. doi: 10.3969/j.issn.1673-3185.2018.02.004
Abstract:
  Objectives  In this paper, in order to study the flow characteristics and mechanism of three-dimensional flow around a circular cylinder of finite length,   Methods  a numerical simulation using a Large Eddy Simulation (LES) and vortex structural classification technology is carried out, and the accuracy of the simulation is proven.  Results  When analyzing the flow field, it is found that the length of the recirculation zone is smaller for a circular cylinder of finite length. In addition, the downstream from the free end can suppress the common phenomenon of Karman-Vortex-Street which leads to a loss of drag-coefficient. Compared with the fixed wall at the bottom, the free end surface has a higher influence on the onstream-wise velocity. The 'mushroom' vortex appears in pairs and two original points exist on the free end. The circular cylinder of finite length appears to be strongly three-dimensional with a lower drag-coefficient. Moreover, there is a tip vortex behind the free end and a horseshoe vortex in the cylinder-wall junction.  Conclusions  The results of this paper give a relatively comprehensive description of the flow characteristics of a circular cylinder of finite length, and can provide useful references for relevant research.
Simulation analysis of overpressure value for collective protection system of surface ship
Hongchao CHEN, Kaohua SONG, Jian BAO, Wenjun LUO
2018, 13(2): 35-40. doi: 10.3969/j.issn.1673-3185.2018.02.005
Abstract:
  Objectives  The collective protection system is an essential part of surface ship defense. In order to solve the overpressure value of the collective protection system of surface ships,   Methods  the overpressure value of the collective protection system of an entire ship is calculated by theoretical analysis, a simplified physical model and mathematical model of a foreign frigate are created, and an analysis of the overpressure value of the collective protection system is carried out by simulating the pressure distribution of the entire ship under different wind directions and speeds.  Results  The simulation results show that the pressure distribution of an entire ship is extremely non-uniform, increasing from bow to mast until it reaches the maximum, then decreasing dramatically until it presents negative pressure after the stern. It can be concluded that the overpressure value of a surface ship is influenced by wind direction and speed, and each section of a surface ship's overpressure value should be set according to its pressure distribution.  Conclusions  The simulation results of the overpressure value of a surface ship can provide data to support the design of collective protection systems; combined with the pressure distribution of a surface ship, it can also provide useful references for the design of collective protection systems.
Manned submersible working cabin layout design method under cabin function system constraints and ergonomic constraints
Dengkai CHEN, Yu FAN, Shuai ZHANG, Junlin QU
2018, 13(2): 41-50. doi: 10.3969/j.issn.1673-3185.2018.02.006
Abstract:
  Objectives  The cabin layout of deep sea manned submersibles presents difficult problems, mainly regarding the reasonable arrangement of the equipment and the optimization and adjustment of the working area. Previous cabin designs were based on human muscle fatigue requirements, which easily led to the excessive concentration of equipment beyond the limited space of the phenomenon. This also caused such problems as insufficient space for the installation, use and maintenance of equipment. A two-goal-oriented design method focusing on cabin function and ergonomics may avoid these problems.  Methods  In this paper, we propose a layout design method based on two constraints, forming a deep sea submersible cabin layout design flow by analyzing the cabin function constraints and ergonomic constraints under two kinds of guidance. We take the 'Jiaolong' submersible cabin layout design as an example in accordance with the proposed process for program design, and use the JACK analysis system and other tools for human-computer comprehensive evaluation.  Results  This program can provide a comfortable, safe and labor-saving working environment for divers. The proposed layout design methods are reasonable and effective.  Conclusions  Research into the cabin function and ergonomics-oriented method can solve the problem of the small spatial layout of deep sea submersibles, and provide references for the similar layout design of small space and multi-equipment cabins.
Ship Structure and Fitting
Peridynamic model for submarine surfacing through ice
Liyu YE, Chao WANG, Chunyu GUO, Xin CHANG
2018, 13(2): 51-59. doi: 10.3969/j.issn.1673-3185.2018.02.007
Abstract:
  Objectives  With deepening research on the geographical and climatic environment of the Arctic, the political and military value of submarines in the region has been well recognized. Although the thick ice in the Arctic provides natural protection for submarines, it also poses a risk to submarines during the ice surfacing process. A method for accurately predicting the ice surfacing process and transient ice loads can be the most important issue in the design of submarine shells and choice of ice thickness.  Methods  In this paper, a numerical method for dealing with the submarine and ice contact problem is developed. First, the peridynamic theory on the capture of material fractures is briefly introduced and the feasibility of peridynamics in modeling the ice failure problem is discussed. To reflect the physical reality of submarine-ice interaction, a contact detection algorithm is established to prevent the interpenetration of the submarine surface and ice material particles, and a method for calculating the contact load is introduced. Finally, based on peridynamics and the contact detection algorithm, a numerical program for predicting submarine-ice interaction is compiled. Using the DARPA SUBOFF submarine model, the ice surfacing process of a submarine is simulated.  Results  The results show that this method can vividly capture the ice failure process, which corresponds to observations of the ice surfacing process of American nuclear submarines, and the dynamic ice load can be calculated over time.  Conclusions  This method provides new concepts in the study of submarine-ice interaction, and its results support the optimal shell structure design of arctic submarines.
Vibro-acoustic characteristics of typical periodically stiffened plate based on spatial harmonic expansion method
Shuang GAO, Xiang ZHU, Tianyun LI, Weiping HE, Jianhui WEI
2018, 13(2): 60-69. doi: 10.3969/j.issn.1673-3185.2018.02.008
Abstract:
  Objectives  One-way periodic stiffened plates are widely used in ship structures, and their vibro-acoustic characteristics provide a theoretical reference for the analysis and optimization of the sound and vibration characteristics of stiffened plates.  Methods  Considering the force and torque of the stiffeners to the plate, along with the coupling effect between the fluid acoustic medium and the plate, a structural dynamic model of infinite one-dimensional and two-dimensional periodically stiffened plates is established. The spatial domain is transformed into a space wave number domain using the Fourier transforms method. The vibration equation of the stiffened structure is deduced using the constructor, Poisson's formula and periodic function. The analytical solution of the motion equations of typical periodic stiffened plates is obtained and calculated under a time-harmonic point force or harmonic excitation. Combined with the stationary phase method, the far field radiated sound pressure can be obtained. The influence of the torque of the stiffener, excitation types, excitation locations, plate thickness, periodicity spacing and parameters of stiffeners on the sound radiation characteristics of three different models of periodic stiffened plates are numerically quantified.  Results  The torque of the stiffener has a lesser effect on structural vibration characteristics. The influence of the stiffener parameters on the phonon crystal band gap can be used to attenuate the vibration at certain peak frequencies. The excitation load on the strong structural components can effectively weaken the vibration. The periodicity spacing and parameters of the stiffeners have obvious effects on structural vibration characteristics.  Conclusion  The underwater acoustic vibration characteristics of reinforced plate structures can be effectively optimized by the reasonable setting of the excitation types and parameters of the stiffeners.
Influence factors analysis of flow-induced vibration of elbow in piping system
Bing KE
2018, 13(2): 70-75. doi: 10.3969/j.issn.1673-3185.2018.02.009
Abstract:
  Objectives  As important parts of any piping system, the elbows are one of the main factors causing vibration. To have a better understanding of Flow-Induced Vibration(FIV) of elbows in piping system.  Methods  In this paper, the diameter, curvature radius, bending angle are chosen as variables, and a study of turbulence flow-induced vibration of elbow by a combined method of finite element numerical calculation and experiment is carried out, so as to obtain the effect of different curvature radius, bending angle on the fluctuating pressure and the structural vibration response of pipeline elbow under variable flow velocity.  Results  The numerical and experimental results show that the effect of the curvature radius and flow velocity on the FIV of an elbow is significant; with the increase of the curvature radius and decrease of flow velocity, the FIV decreases.  Conclusions  The research results of this paper can provide useful references for the acoustic design of piping systems.
Analysis of free vibration characteristics of thin rectangular plate with typically-shaped central opening
Jun ZHANG, Tianyun LI, Xiang ZHU, Wenjie GUO, Fan CHEN
2018, 13(2): 76-83. doi: 10.3969/j.issn.1673-3185.2018.02.010
Abstract:
  Objectives  A large number of structures with openings are used in engineering projects, which is of great significance for studying the vibration characteristics of plates with openings.  Methods  By introducing an improved Fourier series, the permissible displacement function of rectangular plates with openings is simulated. By using displacement springs and angle springs, arbitrary boundary conditions are simulated. While obtaining the overall energy functional, the kinetic energy and strain energy of the opening part are subtracted. Based on the Rayleigh-Ritz method, the Lagrange energy functional of the structure is constructed and the variational extremum of unknown coefficients in the Fourier series obtained, transforming the original vibration problem into a problem of eigenvalue equations. The paper studies the influence on the free vibration of rectangular plates with different shaped and sized openings.  Results  A comparison with the results of finite element software ANSYS shows that the current method is accurate and reliable,  Conclusions  providing a reference for practical engineering.
Optimization of natural frequency of laminated composite rudder
Jiatong WU, Min SHI, Chunyu REN
2018, 13(2): 84-90. doi: 10.3969/j.issn.1673-3185.2018.02.011
Abstract:
  Objectives  A rudder structure will inevitably vibrate while a ship is at sea. This is why it is necessary to make the first order natural frequency and working frequency of a rudder staggered through reasonable design.  Methods  This paper discusses the problem of optimization for the first order natural frequency of composite rudders in 3 aspects. Finite element software ABAQUS is used to build a simulated model of a composite rudder. Initial design parameters are provided to calculate the natural frequency. Ten types of skeleton layouts are designed and compared with each other, and an optimized design is obtained. Then, with the help of Isight software, the gradient optimization algorithm NLPQL is used to optimize the thickness of the skeleton and the LSGRG algorithm is used to obtain the optimal fiber orientation ply thicknesses. Finally, 10 types of ply sequence are designed.  Results  The results show that the first order natural frequency of the rudder is increased by 169.19% and its weight decreased by 16.63%.  Conclusions  The ideas and methods proposed in this paper are feasible for the optimization of the first natural frequency of a composite rudder, and a satisfactory design scheme can be obtained.
Test method of Poisson's ratio for low modulus elastomer
Jun ZHOU, Zhiyuan MEI, Yongli WANG, Xiaosong ZHOU
2018, 13(2): 91-96, 122. doi: 10.3969/j.issn.1673-3185.2018.02.012
Abstract:
  Objective  There are many problems in the axial load of low modulus and high elasticity samples, such as large deformation and poor uniformity, and it is difficult to accurately measure the Poisson's ratio of such material using the conventional resistance strain test method.  Methods  In this paper, based on the theory of elastic mechanics, the expressions of the volume compression modulus, elastic modulus and Poisson's ratio of a cylindrical low modulus elastomer with radial rigidity constraint are derived. On the basis of the above theoretical analysis, this paper puts forward a test method for the axial loading Poisson's ratio of a steel sleeve radial constraint, and carries out related experimental research work on steel tube restraint to determine the accuracy and effectiveness of the final verification test method. Finally, a simulation analysis of the buoyancy material model test process is carried out, and the wall thicknesses of different steel sleeves are simulated to illustrate the influence of wall thickness on the test.  Results  Research into the low modulus elastomer Poisson's ratio test method can obtain the accurate measurement of the Poisson's ratio of the material, making it suitable for studying the mechanical properties of the low modulus and elasticity modulus of the elasticity of material.  Conclusions  The research results of this paper can provide valuable references for related testing.
Clustering-based classification method of loading schemes of multi-span beams under multiple patch loading
Guangji ZHU, Yuansong HE, Qi WAN, Jun LIU, Yuansheng CHENG
2018, 13(2): 97-102. doi: 10.3969/j.issn.1673-3185.2018.02.013
Abstract:
  Objectives  It is of great significance to classify a large number of loading schemes quickly and accurately, and obtain loading schemes with similar structural design requirements or decide the structural design of multi-span beams.  Methods  In this paper, a classification method for the loading schemes of multi-span beams under multiple patch loading is proposed. For the given multi-span beams and vehicles, the worst-case analysis of multi-span beams under multiple patch loading is used to obtain the maximum bending moment, maximum shear force and maximum deflection of a multi-span beam under all possible loading schemes; then the XB index and fuzzy C-means (FCM) algorithm are used to classify the loading schemes according to the above results. For three-span beams and four-span beams, the influence of the ratio of span and moment of inertia on the classification results is analyzed.  Results  The numerical results show that the classification of multi-span beams with different structural forms is not exactly the same. The maximum margin of error between the results of multi-span beam structures with variable span ratio or variable moment of inertia ratio calculated with the classification of equal span rigidity multi-span beams and actual worst-case results is less than 2%.  Conclusions  The relationships between the loading schemes of multi-span beams under multiple patch loading is analyzed, providing a reference for the design of deck structures under multiple patch loading.
Marine Machinery, Electrical Equipment and Automation
Preliminary design of rim-electric driven propeller and effect factor analysis on cogging torque
Ping YU, Junwei ZHOU, Guozheng ZHANG
2018, 13(2): 103-109. doi: 10.3969/j.issn.1673-3185.2018.02.014
Abstract:
  Objectives  Cogging torque has an important influence on the blade vibration of a Rim-Electric Driven Propeller (REDP). In order to investigate a method for reducing the cogging torque of REDP, this paper analyzes the combination of slot number, pole number, tooth shape and pole arc coefficient on the influence of cogging torque.  Methods  First, according to the Ka4-50 propeller model parameters and the design standards of the Permanent Magnet Brushless DC Motor, a 36-slot and 26-pole driven motor is designed. The magnetic circuit calculation software Maxwell Rmxprt is then used to analyze the influence of different slot number and pole number combinations, tooth shape and pole arc coefficient on the motor.  Results  The results show that for a frictional slot and concentrated windings motor, the amplitude of the cogging torque is inversely proportional to the lowest common multiple. Among opening slots, closed slots and half-closed slots, half-closed slots have the greatest torque, opening slots have less and closed slots have the least. The influence of pole arc coefficient on cogging torque shows a fluctuation rule. In the design, it is necessary to find the extreme pole arc coefficient corresponding to the minimum value of the cogging torque through specific analysis.  Conclusions  This paper provides references for the overall design of REDP and a theoretical basis for further exploring the influence of the motor on the vibration and noise of REDP.
Feasibility research for design of marine propellers and energy recovery turbines
Hang LI, Long YU
2018, 13(2): 110-115. doi: 10.3969/j.issn.1673-3185.2018.02.015
Abstract:
  Objectives  This paper develops a design method for a new concept energy conservation device.  Methods  An energy recovery turbine is arranged in the slipstream of a marine propeller with the generator driven by the slipstream of the propeller, in such a way that the turbine converts the kinetic energy into electricity so as to reduce the energy consumption of the ship. In this paper, the propeller and aft turbine are holistically designed. The Vortex Lattice Method is applied in the propeller design while an in-house Matlab code based on the Modified Blade Element Momentum Theory (M-BEMT) is used for turbine performance evaluation. The turbine blade is design and optimized by a Genetic Algorithm (GA). An application case study is completed and a combined thruster solution put forward. The efficiency in open water is simulated on the basis of CFD.  Results  At the same advance coefficient, the efficiency of the combined thruster is about 4% higher than that of the original propeller, with a slight increase in absorbed power. By adjusting the rotational speed, the combined thruster has lower power consumption of around 3.43%.  Conclusions  The feasibility of this new concept device is validated by comparison with that of the original propeller.
Thermal dynamic calculation method and characteristic analysis of marine secondary circuit system under all operating conditions
Jialin CUI, Zichun YANG, Lei ZHANG
2018, 13(2): 116-122. doi: 10.3969/j.issn.1673-3185.2018.02.016
Abstract:
  Objectives  In order to carry out the comprehensive thermal calculation of the marine secondary circuit systems of nuclear power plants conveniently and efficiently,  Methods  a thermal dynamic calculation method under all operating conditions is proposed and a mathematical model of a secondary circuit system established on the basis of the features of the secondary circuit systems of marine nuclear power plants, the characteristics of main steam turbine sets and accessory equipment, and the calculation results of equipment parameters and heat balance under several typical operating conditions. Several powers of main steam turbine are set evenly between minimum and maximum operating conditions, and the power of the main steam turbine is used as the input argument. The thermal parameters of the equipment change synchronously through a several-layer nesting cycle. The changing laws of such parameters as the steam consumption of each main piece of equipment, temperature of the steam and water in each heat exchanger, and overall steam consumption and efficiency with respect to the operating conditions are obtained. The reasons for the above-mentioned changing laws are analyzed and the calculation values compared with the design values.  Results  The results show that the margins of error of the system parameters are small, which satisfies calculation accuracy requirements.  Conclusions  The proposed method and changing laws in this paper provide a reference for the study of the parameter matching characteristics of secondary circuit systems.
Influence factor analysis on anti-whip restraint of ship's main steam pipeline based on LS-DYNA
Meixin XUE, Pengju YANG, Cuina ZHAO
2018, 13(2): 123-128. doi: 10.3969/j.issn.1673-3185.2018.02.017
Abstract:
  Objectives  To address the high-energy pipe whip design problem faced by the nuclear power plants of ships,  Methods  LS-DYNA software is used to establish a nonlinear finite element model of the main steam pipe and U-shaped whip restraint device(i.e U-bolt)so as to simulate the dynamic whipping process.  Results  It is found that the whip restraint rejection force reaches its maximum peak at the primary collision and reduces towards the static support reaction after several collisions. Within a range of 40 -120 mm, the maximum rejection force increases as the initial clearance between the pipe and U-bolt whip restraint device is increased, while the increasing slope gradually reduces and the dynamic magnification factor comes to a limit of 1.74. Within the range of 1.5D-2.5D, the maximum rejection force decreases slightly by 2.5% as the relative axial location between the pipe and U-bolt whip restraint device is increased. Compared with the U-bolt whip restraint, the U-shaped plate can not only reduce the cross-sectional area by 16.3% but also lessen the maximum rejection force by 5.5%.  Conclusions  The analysis results show that the maximum rejection force of the U-shaped plate whip restraint device has a positive correlation with the initial clearance of the restraint, but there is a limit to the dynamic magnification factor, the square section U-shaped plate whip restraint device has greater bearing capacity.
Longitudinal vibration model and analytic study of submarine propulsion shafting
Da XU, Baohong HAN, Wanheng HE, Jinfeng YU, Weikai LI
2018, 13(2): 129-134. doi: 10.3969/j.issn.1673-3185.2018.02.018
Abstract:
  Objectives  In order to solve the problem of the longitudinal vibration of submarine propulsion shafting,  Methods  complex submarine propulsion shafting is simplified to a uniform stepped shaft continuum model, Wave Propagation Analysis (WPA) is used and the longitudinal vibration transfer relationship of each axis is deduced. Combined with the actual propulsion shafting boundary conditions, the steady state response of propeller shaft longitudinal vibration under propeller excitation is obtained.  Results  The reliability of the model is verified by comparing the theoretical calculated value with the finite element software simulation results and experimental test data, proving that it can be used for the longitudinal vibration analysis of propulsion shafting. Dimensionless formulas for the first natural frequency of the longitudinal vibration of submarine propulsion shafting are deduced, providing convenience for further analysis.  Conclusions  The results have definite value for engineering applications.
Precision measurement of ship's induced vertical magnetic signatures
Chengbao GUO, Weichang ZHOU
2018, 13(2): 135-139. doi: 10.3969/j.issn.1673-3185.2018.02.019
Abstract:
  Objectives  For the precision measurement of a ship's induced vertical magnetic signatures, a new method combining numerical analysis and geomagnetic simulating coils is proposed.  Methods  After the currents in the geomagnetic simulating coils are calibrated by numerical analysis, the coils are used to measure the ship's induced vertical magnetic fields. A simulation experiment installation is established and an evaluation test performed on a magnetic ship mockup.  Results  The results indicate that the difference between the measurement values and standard values of the ship mockup's induced vertical magnetic fields falls within 4%,  Conclusions  which validates the theory that this technique can be used for the precision measurement of a ship's induced vertical magnetic fields with high practical value.
Weapon, Electronic and Information System
Numerical simulation of transient electromagnetic response of aircraft to lightning strikes
Qianhua LI, Xi CHEN, He'nan LIU, Zhijun HU, Yong PENG, Zhongquan LONG, Jun GUO
2018, 13(2): 140-148. doi: 10.3969/j.issn.1673-3185.2018.02.020
Abstract:
  Objectives  With the rapid development of space technology, launching aircraft at sea has gradually become a future development trend. Aircraft flying in the atmosphere will sometimes encounter lightning strikes, which can cause damage to airborne equipment.  Methods  In response to this issue, two aircraft models (one with a gap and one with no gap) are built. Based on the CST transmission line matrix method, the induced electric and magnetic fields, surface current and induced current distribution of the cables of the two aircraft models are studied. At the same time, the changes in induced current in cables of different lengths are studied.  Results  For the same aircraft model, the surface electric and magnetic fields and internal electric and magnetic fields at the same axial position are not only different in induction peak value but also in change trend. The gap has little effect on the surface electric and magnetic fields of the aircraft, but the influence is particularly obvious inside the aircraft. The gap of the aircraft has a great influence on the induced current of the cable. Compared with the model with a gap, the single wire induced current peak of the model with no gap decreased by 1 000 times, and the current peak of the coaxial wire decreased by 15 times.  Conclusions  The research results of this paper can provide references for understanding the electromagnetic effect of lightning strikes on aircraft, and the results will be helpful for carrying out the next step in lightning protection work.