2017 Vol. 12, No. 1
 Numerical analysis of the scale effect of the nominal wake field of KCS…ZHANG Haipeng, ZHANG Donghan, GUO Chunyu, et al(1) Numerical study of hydrofoil tip vortex fluid field…PU Jijun, XIONG Ying(8) Effect of bow spray strips and Ω-type freeboard on high-speed boats…WEI Chengzhu, LI Yinghui, YI Hong(14) Wave-making resistance reduction characteristics based on spherical bow configuration…ZHANG Wenshan, LU Xiaoping(21) Maneuverability prediction for a ship with full-revolving twin propellers…WU Xingya, GAO Xiaopeng(27) Analysis of correlation between destroyer seakeeping and motion sickness in human factors…XIONG Hu, LU Xiaoping(32) 3D virtual human rapid modeling method based on top-down modeling mechanism…LI Taotao, FANG Xiongbing, LIN Rui, et al(38) Research progress of anti-icing/deicing technologies for polar ships and offshore platforms…XIE Qiang, CHEN Hailong, ZHANG Jifeng(45) Research development of buckling and ultimate strength of hull plate and stiffened panel…CHEN Yanting, YU Changli, GUI Hongbin(54) Reliability calculation method of longitudinal ultimate strength of ships under extreme sea conditions…ZHANG Zengyin, ZHAO Yao(63) Deformation analysis of horizontal stiffened cylindrical shells under the effects of gravity…LIU Dong, ZHANG Yuelin, CHEN Wu(72) Optimization of pre-swirl stators based on CFD for a chemical product carrier…HAN Cong, FU Huiping, MA Ning, et al(78) Theoretical and experimental research on influencing factors and rules of flow-induced rudder system vibration…XIAO Qing, HU Gangyi, XIE Junchao(84) GFRP and steel compounded structure subjected to impact by high velocity projectiles…ZHANG Yuanhao, CHEN Changhai, ZHU Xi(93) Research into energy absorption of liquid cabin subjected to close-range explosion…LI Siyu, LI Xiaobin, ZHAO Pengduo, et al(101) Phase-conjugate arrays and phase-conjugated fields produced by the arrays…LI Sheng, LI Ting, LIU Song(107) Effect of longitudinal vibration of fluid-filled pipe with elastic wall on sound transmission character…DONG Peng, CHEN Zhigang, GONG Qiang, et al(116) Response mechanism of impact load based on marine shafting-oil film-stern structure system …DONG Liangxiong, YANG Yi, GAO Junkai, et al(122) Method for rudder roll stabilization control by maintaining ship speed …LIU Zhiquan, JIN Hongzhang(128) Application of novel linear active disturbance rejection control in dynamic positioning control system of vessels…JIN Yue, YU Menghong, YUAN Wei(134)
The viscous self-propulsion flow fields of a model-scaled 55k DWT chemical product carrier fitted with a rudder-bulb-fin and a pre-swirl stator are numerically simulated based on the CFD general code FLUENT. The energy saving effects of stators are evaluated through the increase of propulsive efficiency. It is found that the computed changing tendencies of almost all self-propulsion factors after being equipped with a stator are the same as in the experiments, such as a decreased revolution rate, increased thrust deduction and mean wake. A wake energy analysis is also conducted to verify the energy-saving effects of stators, and it shows that the stator decreases the flow of kinetic energy behind the propeller through its contra-propeller pre-swirl. Next, an optimization of pre-swirl stators is conducted by CFD. Aside from the prototype stator, three modified stators are designed and the self-propulsion characteristics with these stators are also numerically simulated. The increase order of the evaluated energy-saving effects of these modified stators is seen to be the same as in the design idea. The case with the highest propulsive efficiency shows the largest increase of Ktotal before the propeller and the largest decrease of Ktotal behind the propeller relative to cases without stators.
Flow-induced rudder system vibration has a great influence on the stealthiness of underwater vehicles. In order to study the vibration characteristics of rudder systems, a mathematical model of a binary linear flutter rudder system is built according to a simplified rudder system structure. Next, the conditions of low speed flutter of the rudder system are determined, and the main influence factors and control rules of the low speed flutter are obtained. In addition, flow-induced vibration tests of the rudder model are made in a gravitation water tunnel, and a study is made of the influences on the rudder system caused by variations in such main parameters as support stiffness, torsional stiffness, mass center position and stiffness center position. The results show that the structural design has a great influence on flow-induced rudder system vi-bration. The flow-induced vibration of the rudder system can be effectively suppressed through the match-ing design of such parameters as the frequency ratio of heave motion and torsion motion, the ratio of the structural mass and added mass, and the positions of the stiffness center, mass center and chord center.
To explore the influence of steel and GFRP structural configuration on the perforation-resis-tance of a composite armor system of warship bulkhead, a series of high velocity ballistic impact experi-ments are performed.The outer and inner composite armor systems of warship bulkhead are simulated us-ing homogeneous steel plates prefaced and backed with composite laminates, respectively. Failure modes and energy absorption for the two types of combined targets are analyzed and compared with each other. Based on the experimental results, the compounded structure subjected to the impact caused by cube pro-jectiles is simulated using finite element program ANSYS/LS-DYNA, where the process of penetration is investigated and compared with experiment results. It is observed that the numerical results are in good agreement with the experimental results; the failure modes for the composite armors in the two types of com-bined targets are mainly the shear punch failure of steel plates and the fiber shear fracture of GFRP, while the GFRP in the combined target consisted of front steel plates and composite backed armors also has ten-sile failure of fibers; the combined target consisted of front steel plates and composite backed armors ab-sorbs much more energy than that consisted of front composite armors and steel backed plates.
In order to study the energy absorption of different parts of a liquid cabin under a close-range explosion, a fluid-structure coupling model is built on the basis of experiments, and the deformation of the bulkhead and energy absorption ratio of different parts of the liquid cabin are analyzed, in which the influence of the water, bulkhead thickness ratio and water thickness are also discussed. The results show that the existence of a liquid medium can change the energy absorption model of a cabin. The total energy absorption is mainly affected by the front bulkhead thickness and water thickness, and alterations to the bulkhead thickness ratio or water thickness can also affect the deformation model of the bulkhead and energy absorption ratio of different parts of the cabin. A logical explanation of the energy absorption mechanisms of the liquid cabin is proposed, and some useful suggestions for designs are given.
Phase Conjugate (PC) arrays can make sound waves travel backwards to converge, which can then be used to build the image of a noise source. This paper reviews and analytically studies three types of PC array (monopole PC array (PC/M), dipole PC array (PC/D) and perfect PC array (PC/P)) and the phase-conjugated fields produced by the arrays. The relationship between the sound field produced by the source and the phase-conjugated fields produced by the arrays are discussed. The various PC schemes are compared and analyzed from the evanescent wave component and the propagating wave component. The metrics of the focusing properties of PC arrays and the effects of the array element spacing on the focusing properties are discussed. The spatial resolutions of various PC schemes with different distances between array and source are studied numerically with linear arrays. The element deviation is also discussed. A numerical simulation shows that PC/D with half-wavelength element spacing is effective at near field focusing, and PC/M with half-wavelength element spacing is effective at a greater distance.
When one end of a fluid-filled pipe with an elastic wall is fixed and a harmonic force effect acts on the other end, a steady longitudinal vibration will be produced. Compared to the pipeline resonance mode, the amplitude of the steady longitudinal vibration of an elastic pipe is greater, and the effect on the sound is also greater. The study of the steady longitudinal vibration of pipes can better describe the effects of fluid-filled pipelines on the radiation sound field of the pipe opening. Through the contrast between the analysis calculation of the equivalent beam model and the experimental results, the accuracy of the equivalent beam model for the calculation of the steady longitudinal vibration of pipelines is verified, and a method of isolating the steady longitudinal vibration state is proposed and verified.
The anti-impact ability of shafting directly affects the stability and security of a ship's power transmission, and it cannot be ignored that large-scale effects on ships have an influence on the interaction intensity of the impact load. Based on the marine shafting-oil film-stern structure system, the average im-pact load, impact amplitude and orbit of the axle center are analyzed, and the range of shafting speed and load for safe running is determined. The results show that the law of interaction intensity changing with the load is different at different rotation speeds. The interaction intensity of shafting with loads depends on the stern shaft speed and impact intensity, and can be approximated as a function for assessing load carrying ca-pacity.
A ship navigating on the surface of the water may experience greater resistance, adversely affect-ing its speed and leading to energy loss. The added resistance of surface ships in both still water and waves are investigated, and the computation method of total speed loss is presented. An autopilot system is intro-duced to constrain the speed loss, and course keeping and rudder roll stabilization sliding mode control laws are proposed according to a compact control strategy. The two working conditions of "heading" and "heading plus anti-roll" are discussed, including roll stabilization, heading error, speed maintenance and rudder abrasion. The results show that the speed can be effectively maintained using this method, and from a commercial point of view, the fin-rudder roll stabilization control is not recommended for vessels equipped with both fins and rudders.
Aiming at the problem in which a vessel's dynamic positioning system can control it at an expected position, a novel linear active disturbance rejection controller is designed to solve the problem of poor dynamic performance due to the omission of a tracking differentiator. Based on the advantages of linear and nonlinear tracking differentiators, an improved tracking differentiator is designed which can track the differential signal and degrade the effects of noise; it constitutes a novel Linear Active Disturbance Rejection Controller (LADRC). The simulation results show that the novel LADRC based on the improved tracking differentiator has strong robustness, high control accuracy and good dynamic performance compared with the traditional LADRC.
In order to study the scale effect of the nominal wake field, the viscous flow field of KCS is studied without considering the free surface effect, and the nominal wake fields of KCS at different scales including full scale are solved numerically using the RANS method and the SST k-ω turbulence model. By comprehensively comparing the computed results with experimental data, the scale effect of the nominal wake field is further investigated. This shows that the reciprocal of the mean axial wake fraction at each radius exhibits a near-linear dependence on the Reynolds number in a logarithmic scale; for the nominal wake field of the propeller disc of KCS without a propeller, two wake peaks exit, and the amplitude of the axial wake peak decreases with the increase of the Reynolds number, which is conducive to a decrease in propeller exciting force and propeller cavitation; the scale effect of the small scale model is more obvious, and the scale effect of the mean axial wake fraction in the inner area is stronger than it is in the outer area.
Three different models, k-ω, DES and LES, are conducted in the analysis of the tip vortex flow field. In order to reduce the discrete error induced by the grid, mesh refinement is applied to the area of the tip vortex core in numerical simulations. The axis and tangential velocities of the tip vortex flow field with no cavitation are calculated, and the calculated velocities agree well with the experimental results. On the basis of this process, the influence of vortex roll-up on the tip vortex pressure filed is discussed, and bubble static equilibrium is proposed by which the tip vortex cavitation inception number is computed.
A high-speed boat may encounter severe wave-making at the bow and become wetter at high speed. Some measures can be taken to overcome these disadvantages. In order to compare the effect of bow spray strips and Ω-type freeboards on a high-speed boat, hull wetness, resistance, hull motion, stability and the restoring moment of the heel at high speed of models with these two kinds of auxiliaries were calculated and measured. CFD methods and model tests were adopted. Both of these two auxiliaries can reduce hull wetness, and the model with a Ω-type freeboard has a better initial stability and larger restoring moment of the heel at high speed. A free running model test also indicates that the Ω-type freeboard has a fine performance.
Nowadays, the mechanism of a bulbous bow on resistance reduction is still ambiguous. By carry-ing out a study of wave-making resistance based on spherical bow configuration, we can reveal the truth of the problem and find out the effect of reducing resistance and suppressing waves of a bulbous bow on a sur-face combat ship. As such, the study is fundamentally meaningful. As to ship type DTMB 5415, CFD soft-ware STAR-CCM was utilized to analyze the effect and mechanism of the bulbous bow's main configuration parameters on wave-making resistance. To this end, several groups of extended bulbous bows with extend-ed reach and various radius parameters were first set up. Next, analyses were carried out of the variation of resistance and the mechanism of the bulbous bow on resistance reduction, which associate with the known experimental data and CFD calculated data. The final results show that, in certain circumstances, the Froude number, vertical position and radius of the bulbous bow have vital and obvious influences on wave-making resistance.
To predict the maneuverability of full-revolving propeller ships, this paper analyzes the propeller force and establishes MMG equations for controlling motion mathematical models that are suited to the full-revolving propeller model, in accordance with the modeling method of the separating ship motion model and taking into account the special nature of the force and flexibility of a full rotation in the horizontal plane of a full-revolving propeller. Secondly, hydrodynamic force derivatives for the ship model are obtained by simulating the model's PMM movement, and the controlling Ordinary Differential Equation (ODE) is solved using the four-stage Rung-Kuta method. Finally, the numerical simulation of a certain ship's rotating motion and its zigzag test in still water is obtained, and the prediction results are compared with that of a self-running model. It is found that the simulation results agree well with the trial results, and the effectiveness of the ship motion model for the full-revolving propeller model is validated. In brief, this paper provides a reliable and effective method of predicting the maneuverability of full-revolving propeller ships.
Seakeeping is not only an important indicator of the overall performance of a ship, it also has a direct impact on the occurrence of motion sickness among ship personnel; as such, a good seakeeping design is the basis for guaranteeing the crew's comfort and work performance. In this paper, a seakeeping calculation program using the theory of the strip method is written to calculate the seakeeping of the DTMB 5415 standard model, and the vertical acceleration response at the bow and the center of gravity in head waves and under different speeds are obtained. Next, the effects on motion sickness of the vertical accelerations of DTMB 5415 corresponding to the destroyer's heaving are analyzed, and the numerical relationship of motion sickness with the destroyer's seakeeping performance is obtained. The results show that the calculated vertical accelerations at the bow and center of gravity are correct, the accuracy of which satisfies the requirements of motion sickness prediction; and the calculated regularities of the motion sickness are reasonable, and can be applied to analyze and predict the incidence of motion sickness on a ship, as well as to improve human factors in the hull form design of destroyers.
Aiming to satisfy the vast custom-made character demand of 3D virtual human and the rapid modeling in the field of 3D virtual reality, a new virtual human top-down rapid modeling method is put for-ward in this paper based on the systematic analysis of the current situation and shortage of the virtual hu-man modeling technology. After the top-level realization of virtual human hierarchical structure frame de-sign, modular expression of the virtual human and parameter design for each module is achieved gradu-al-level downwards. While the relationship of connectors and mapping restraints among different modules is established, the definition of the size and texture parameter is also completed. Standardized process is meanwhile produced to support and adapt the virtual human top-down rapid modeling practice operation. Finally, the modeling application, which takes a Chinese captain character as an example, is carried out to validate the virtual human rapid modeling method based on top-down modeling mechanism. The result demonstrates high modelling efficiency and provides one new concept for 3D virtual human geometric mod-eling and texture modeling.
The polar regions present adverse circumstances of high humidity and strong air-sea exchange. As such, the surfaces of ships and platforms (oil exploiting and drilling platforms) serving in polar regions can easily be frozen by ice accretion, which not only affects the operation of the equipment but also threatens safety. This paper summarizes the status of the anti-icing/deicing technologies of both China and abroad for polar ships and offshore platforms, and introduces the various effects of ice accretion on polar ships and offshore platforms, and the resulting safety impacts. It then reviews existing anti-icing/deicing technologies and methods of both China and abroad, including such active deicing methods as electric heating, infrared heating and ultrasonic guided wave deicing, as well as such passive deicing methods as super hydrophobic coating, sacrificial coating, aqueous lubricating layer coating and low cross-link density (with interfacial slippage) coating, summarizes their applicability to polar ships and offshore platforms, and finally discusses their advantages/disadvantages.
Buckling and ultimate strength of hull plate and stiffened panel are important contents in the de-sign of ship structures, have achieved plenteous results in recent years. The research development of buck-ling and ultimate strength of steel hull plate and stiffened panel in the past decade at home and abroad is re-viewed for the convenience of carrying out studies and researches. The case of static loading is emphatical-ly described, the cyclic loading and dynamic loading are also introduced. A systematical overview is pre-sented for intact structures and damaged structures under single load or combined loads, in accordance with four kinds of research methods, which are experiment, numerical computation method, analytical method and comprehensive approach. The superiority and inferiority of each research method are assessed. Significant achievements are summarized, and six further problems are identified for the future study.
Building a large ship in an overall sea area is a trend in shipbuilding. As such, it is necessary to take into account the influence of extreme waves in the calculation of a ship's longitudinal ultimate strength reliability. The general method of load calculation does not take into account the effects of special wave loads under extreme sea conditions. In addition, for reliability analysis, extreme loads have more complicated random variables. The general method of ship reliability calculation requires these variables to obey a certain distribution, which may mean that the original method cannot be used. From the perspective of navigational limit, the maximum value of the wave bending moment is greater than that of the conventional wave bending moment which does not take the impact of extreme wave sea conditions into account. The experimental data shows that the wave moment calculation method considering extreme wave sea conditions can to some extent reflect the wave loads of ships more realistically. Secondly, by considering the characteristics of different reliability calculation methods and using case calculations, this paper gives a selection of calculation methods of the longitudinal ultimate strength reliability of ships under extreme sea conditions.
In order to study the deformation of submarine pressure hulls under the effects of gravity, a sim-ple calculation formula of the deformation of the free ends of stiffened cylindrical shells is derived based on moment theory and non-moment theory, and the calculated results are compared with the results of Finite Element Analysis (FEA) which tests the reliability of the formula. The results show that when a thin-wall cylindrical shell simply supported at the bottom is affected by its own gravity, the deformation degree at the free end is directly proportional to the fourth power of the inner diameter of the cylindrical shell, and in-versely proportional to the square of the wall thickness; for cantilever cylindrical shells, the gravity load has little effect on the roundness of the free end plane. With the nonlinear increase of distance between the free end and fixed supporting end, the increase rate increases gradually. With the increase of the inner di-ameter of the cylindrical shell, the deformation degree of the free end decreases gradually. When the inner diameter of the cylindrical shell is 0.75 times its longitudinal length, the deformation degree of the free end is at a minimum, then increases gradually as the inner diameter increases. The gravity deformation calcula-tion of ring stiffened cylindrical shells in a horizontal state and the strengthening measures can provide ref-erences for further study.