检索结果-南通市图书馆

Defence Technology（防务技术） 2022年第6期18卷 995-1005页

作者： Yu-jia Liu Dian Li Hai-liang Hou Zhu-jie Zhao Yue Xie college of naval architecture and ocean engineering Naval University of EngineeringWuhan430033China

In order to study the influence of the bolt joint mode on low-velocity projectiles penetrating the composite protective structure,two bolt joint models which connect the composite target to the fixed frame were designed,the ballistic test of the bolted composite protective structure with limited span was carried out,and the bearing and failure characteristics of the bolted region,as well as the energy dissipation of each part of the structure,were analyzed.The results show that in the condition of lowvelocity impact,there are three failure modes for the bolted composite protective structure subjected to projectile penetration,including failure of the impact point of the composite target,failure of protective structure connecting components and failure of the holes in the bolted region of the composite target;the failure mode of bolt holes in the bolted region has a great influence on the protection performance,and the allowable value of the bearing capacity of the bolted region depends on the sum of the minimum failure load in the failure modes and the friction force;shear-out failure occurring in the bolt holes in the bolted region exerts the greatest effect on ballistic performance,which should be avoided;When simultaneous failure occurs in the bolted region and the free deformation region of the composite protective structure,the energy absorption per unit surface density of the composite protective structure reaches the maximum,which can give full play to its anti-penetration efficiency.

关键词： Impact dynamics Composite protective structure Bolt joint Ballistic test Failure modes

Sagging damage characteristics of hull girder with trapezoidal cross-section subjected to near-field underwater explosion

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2023年第3期21卷 1-13页

作者： Hai-tao Li Xin-ying Zheng Chi Zhang Zhi-yuan Mei Xue-fei Bai Kai Liu college of naval architecture and ocean engineering Naval University of EngineeringWuhan430033PR China

To investigate the overall damage characteristics and failure modes of a warship subjected to an underwater non-contact near-field explosion,a hull girder with a trapezoidal cross-section was designed,manufactured,and tested.The design criteria and parameters were determined according to the similarity criterion.Dynamic responses of the girder freely floating on water were obtained under varying conditions,including stand-off distance,charge mass,and position of attack.Damage morphologies of the girder model were obtained.Based on our analysis,basic conditions for sagging damage of the hull girder are proposed.The aim of this study was to determine an efficient method of attack resulting in the most severe damage to the ship hull.The experimental results show that the girder mainly exhibits a first-order response when the first wet frequency of the girder is close to the frequency of the explosion bubble pulsation.The largest deformation was observed when the underwater explosion occurred directly below the midspan of the girder compared to other explosions of the same intensity at different attack positions.When the ratio of stand-off to maximum bubble radius(λ)satisfies 0.7≤λ<2,the bubble mainly causes sagging damage instead of hogging.Asλdecreases(1≤λ<2),the sagging damage increases under the same charge mass.However,asλdecreases further(0.7≤λ<1),the sagging deformation decreases.This is likely due to the impact of the liquid jet formed by the collapsing bubble,which causes the girder deformation to shift from sagging back to hogging deformation.The initial shock wave excites the high-frequency response of the girder structure but contributes very little to the overall velocity and displacement.However,bubble pulsation typically causes a low-frequency response,which will affect the velocity and displacement of the girder.The low-pressure region of the flow field formed by bubble pulsation and resonant coupling between the girder and the bubble are the predominant causes of damage to the overall girder structur

关键词： underwater bubble girder

Dynamic Analysis of Semi-Submersible Production Platform Under the Failure of Mooring Lines

在线全文

学校读者我要写书评

暂无评论

China ocean engineering 2021年第1期35卷 84-95页

作者： CHUANG Zhen-ju LIU She-wen LI Chun-zheng LU Yu CHANG Xin Naval Architecture and Ocean Engineering College Dalian Maritime UniversityDalian 116026China

This paper quantitatively studies the transient dynamic response of a semi-submersible production platform with the loss of one or several positioning mooring lines.A semi-submersible platform,production risers,and positioning mooring lines are all included in the numerical simulation.Increased motion of the semi-submersible platform,tension variation of the remaining mooring lines/risers and the risk of mooring line or riser clashing are all investigated through fully coupled time-domain analysis.Combined environmental loads are selected from irregular waves and the steady current varying from very rough to extreme sea conditions.Three dimension radiation/diffraction theories and Morison’s equation are applied to calculate first-order wave force and second-order mean drift force of floating semi-submersible platform.Nonlinear time-domain finite element methods are employed to analyze the behavior of mooring lines and risers.Results show that the failure of mooring lines seriously reduce the platform’s stability performance.The tension of the rest lines is also increased accordingly.Remaining lines which are closer to the failed lines will have larger tension increase to compensate.Line-Line distance provides practical information for the risk of clashing investigation.

关键词： mooring line failure the transient response of platform tension variation of mooring line risk of lines clashing coupling effect between platform and mooring system

Influence of Cavity Leakage flow on Corner Separation in a Shrouded Stator Cascade

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2023年第1期32卷 351-365页

作者： KONG Xiaozhi HUANG Tianshuo LIU Yuxin LU Huawei WANG Long Naval Architecture and Ocean Engineering College Dalian Maritime UniversityDalian 116026China Marine engineering college Dalian Maritime UniversityDalian 116026China

The impacts of the cavity leakage flow on the shrouded stator aerodynamic performance were investigated by modelling the annular cascade mainstream with the seal cavity flow path based on the validated numerical method.Meanwhile,the interactions between the cavity leakage and the mainstream were also determined in the current study.The development of hub corner separation under the action of leakage was discussed and the total pressure loss coefficient as well as the entropy-based loss coefficient was employed to evaluate the performance changes at different seal clearances and cavity rotational speeds.The results show that the cavity leakage flow induces a new vortex near the blade leading edge and plays an important role in the development of passage vortex and the size of concentrated shedding vortex.By increasing the seal clearance with more cavity leakage flow rate,an increase in the pitchwise extent of the separation region under 15%span is significant and the total pressure loss in the separation core increases.In addition,with the increase of cavity rotating speed,the starting point of corner separation moves backward,reducing the size and depth of the hub corner separation.The mainstream loss reduction in combination with the entropy increase in the seal cavity causes the entropy-based loss coefficient to perform a trend of decreasing first and then increasing with the cavity speed.

关键词： shrouded stator cavity leakage flow corner separation loss coefficient

Numerical Study on Air Turbines with Enhanced Techniques for OWC Wave Energy Conversion

在线全文

学校读者我要写书评

暂无评论

China ocean engineering 2017年第5期31卷 517-527页

作者： CUI Ying HYUN Beom-Soo KIM Kilwon Department of ocean engineering College of EngineeringOcean University of China Division of naval architecture and ocean engineering Korea Maritime and Ocean University

In recent years,the oscillating water column(OWC) wave energy converter,which can capture wave energy from the ocean,has been widely applied all over the world.As the essential part of the OWC system,the impulse and Wells turbines are capable of converting the low pressure pneumatic energy into the mechanical shaft power.As an enhanced technique,the design of endplate or ring attached to the blade tip is investigated numerically in this paper.3 D numerical models based on a CFD-software FLUENT 12.0 are established and validated by the corresponding experimental results from the reports of Setoguchi et al.(2004) and Takao et al.(2001).Then the flow fields and non-dimensional evaluating coefficients are calculated and analyzed under steady conditions.Results show that the efficiency of impulse turbine with ring can reach up to 0.49 when Ф=1,which is 4% higher than that in the cases for the endplate-type and the original one.And the ring-type Wells turbine with fixed guide vanes shows the best performance with the maximal efficiency of 0.55,which is 22% higher than that of the original one.In addition,the quasi-steady analysis is used to calculate the mean efficiency and output-work of a wave cycle under sinusoidal flow condition.Taking all together,this study provides support for structural optimization of impulse turbine and Wells turbine in the future.

关键词： OWC impulse turbine Wells turbine CFD endplate ring quasi-steady analysis

Three-dimensional elastic exact solution for free vibration of composite cylindrical shells considering ply angle

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Acoustics 2019年第4期38卷 474-489页

作者： TONG Bo LI Yongqing ZHU Xi ZHANG Yanbing college of naval architecture and ocean engineering Naval University of Engineering

In order to obtain the exact free vibration solution of laminated cylindrical shell with arbitrary ply angle,the transfer matrix of transverse displacement and stress was established by combining the layer-wise theory with state space method.Based on the threedimensional elastic theory,the axial and circumferential displacement components were approximated using double helical pattern modes and the free vibration analytic formula of laminated cylindrical shell with arbitrary ply angle under simply supported boundary was derived.The exact form of the free vibration equation was obtained.The validity of the present theoretical method was performed by being compared with the theoretical model from the literature and finite element method.The results show that when the considered frequencies are less than two times the ring frequency,the calculation precision for natural frequency of thin shells is less than 1% and that of the thick shells is less than 2%.For the thick shells,the shell can be divided into multiple layers along the thickness direction,which can effectively improve the calculation precision.The influence of layer angle on the natural frequency was analyzed based on present method,the results shows that when the circumferential mode is low,the natural frequency is parabolic with the increasing of the layer angle and when the circumferential mode is high,the natural frequency increases monotonically with the increasing of the layer angle.The present method is also suitable for homogeneous isotropic shells and orthotropic cylindrical shells.

关键词： method. shells cylindrical

RANS Simulation for the Maneuvering and Control of a Suboff Submarine Model

在线全文

学校读者我要写书评

暂无评论

Fluid Dynamics & Materials Processing 2020年第3期16卷 561-572页

作者： Jinyu Ren Dezhi Xu Jing Xu naval architecture and ocean engineering Wuhan Technical College of CommunicationsWuhan430065China

Submarine maneuverability has been analyzed by means of computational fluid dynamics(CFD).This approach provides an alternative,accurate,and cost-effective method for simulating actual flow.The numerical results show that the numerical simulation of the viscous flow related to a moving submarine based on the RANS equation with a relevant turbulence model can not only provide rich flow field details such as flow separation,but also accurately predict its hydrodynamic performance.The present study indicates that CFD can be used to forecast the submarine’s maneuverability in the initial design stage.The present results will be used in the future as a basis for analyzing methods to reduce the vibration and noise generated by the submarine.

关键词： RANS equations numerical simulations suboff submarine model

Non-uniform rational B-spline based free vibration analysis of axially functionally graded tapered Timoshenko curved beams

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2020年第4期41卷 567-586页

作者： Zhiwei ZHOU Meixia CHEN Kun XIE School of naval architecture and ocean engineering Huazhong University of Science and Technology college of engineering Huazhong Agricultural University

The free vibration of axially functionally graded(FG) tapered Timoshenko curved beams is studied with the numerical approach. By using the non-uniform rational B-spline(NURBS) basis functions, the exact geometry and the generalized displacement?eld are formulated. Variable geometric parameters and material properties, including the curvature, cross-sectional area, area moment of inertia, mass density, and Young’s modulus, are expanded as functions of the coordinate in a parametric domain. Based on Hamilton’s principle, the weak formulation is derived by applying a re?ned constitutive relation which considers the thickness e?ect. Natural frequencies and mode shapes are obtained from the eigenvalue equation. Circular, elliptic, and parabolic curved beams are considered in numerical examples. The obtained results are in good agreement with those in the existing studies and those calculated by the ?nite element software ANSYS.Moreover, the e?ects of the material gradient, taper ratio, slenderness ratio, and heightspan ratio on vibration behaviors are discussed.

关键词： free vibration functionally graded(FG) material non-uniform crosssection curved beam variable curvature thickness effect

Quadratic Dissipation Effect on the Moonpool Resonance

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

China ocean engineering 2017年第6期31卷 665-673页

作者： LIU Heng-xu CHEN Hai-long ZHANG Liang ZHANG Wan-chao LIU Ming college of Shipbuilding engineering Harbin Engineering University college of naval architecture and ocean engineering Jiangsu University of Science and Technology

This paper adopted a semi-analytical method based on eigenfunction matching to solve the problem of sharp resonance of cylindrical structures with a moonpool that has a restricted entrance. To eliminate the sharp resonance and to measure the viscous effect, a quadratic dissipation is introduced by assuming an additional dissipative disk at the moonpool entrance. The fluid domain is divided into five cylindrical subdomains, and the velocity potential in each subdomain is obtained by meeting the Laplace equation as well as the boundary conditions. The free-surface elevation at the center of the moonpool, along with the pressure and velocity at the restricted entrance for first-order wave are evaluated. By choosing appropriate dissipation coefficients, the free-surface elevation calculated at the center of the moonpool is in coincidence with the measurements in model tests both at the peak period and amplitude at resonance. It is shown that the sharp resonance in the potential flow theory can be eliminated and the viscous effect can be estimated with a simple method in some provided hydrodynamic models.

关键词： in-fluid quadratic dissipation viscous effect moonpool sharp resonance

Molecular dynamics simulation of the flow mechanism of shear-thinning fluids in a microchannel

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2024年第4期33卷 516-525页

作者：杨刚郑庭程启昊张会臣 Naval Architecture and Ocean Engineering College Dalian Maritime UniversityDalian 116026China

Shear-thinning fluids have been widely used in microfluidic systems,but their internal flow mechanism is still unclear.Therefore,in this paper,molecular dynamics simulations are used to study the laminar flow of shear-thinning fluid in a microchannel.We validated the feasibility of our simulation method by evaluating the mean square displacement and Reynolds number of the solution layers.The results show that the change rule of the fluid system's velocity profile and interaction energy can reflect the shear-thinning characteristics of the fluids.The velocity profile resembles a top-hat shape,intensifying as the fluid's power law index decreases.The interaction energy between the wall and the fluid decreases gradually with increasing velocity,and a high concentration of non-Newtonian fluid reaches a plateau sooner.Moreover,the velocity profile of the fluid is related to the molecule number density distribution and their values are inversely proportional.By analyzing the radial distribution function,we found that the hydrogen bonds between solute and water molecules weaken with the increase in velocity.This observation offers an explanation for the shear-thinning phenomenon of the non-Newtonian flow from a micro perspective.

关键词： molecular dynamics simulation non-Newtonian fluid microchannel shear-thinning