细长前锥段超空泡航行器高速入水的载荷数值模拟

以具有细长前锥段的超空泡航行器为计算对象,利用动网格技术进行数值模拟,获得高速入水过程中的冲击过载,分析不同入水速度、通气与否时入水冲击过载的变化规律。研究表明通气可以有效地降低轴向过载,但对于法向过载,降载若使用通气方法,还须考虑空化器直径。     

航行器斜入水跳弹现象研究

为避免航行器结构破坏和电子器件失灵,可以利用入水时的跳弹现象减小入水冲击。本文通过实验方法探究了入水条件对航行器入水过程的影响,研究了不同速度和角度下航行器的跳弹/下沉过程,得到了一个可以预测航行器跳弹/下沉的经验公式。撞水瞬间航行器的头部会受到很大的冲击力,利用CFX软件对航行器不同工况入水过程进行了仿真,计算了不同工况下航行器的压力响应曲线,可以为航行器高速入水时减小入水冲击力提供参考。     

着速和着角对水雷入水过载影响的数值仿真分析

为了研究高速水雷入水时受到的过载情况,采用流固耦合仿真软件MSC-Dytran,对水雷击水问题进行数值模拟仿真研究。分别计算了不同入水情况下雷体指定部位的加速度响应随时间的变化。仿真结果表明水,雷冲击载荷随入水速度的增大而迅速增大,入水速度是水雷受到的冲击载荷大小的主要影响因素。对新型水雷的结构设计、引信的设计、水雷装药的安全性设计以及其他元器件的抗冲击设计提供有价值参考。     

弹体入水冲击载荷特性分析

对由MSC.Dytran仿真计算得到的2种不同初始速度入水弹体入水冲击载荷进行了平稳性检验、功率谱、冲击响应谱、高斯特性、高阶统计等特征分析.研究表明,水雷入水冲击载荷是平稳信号并且为非高斯分布,速度是影响冲击载荷信号的主要因素,为弹体抗冲击总体设计提供依据.     

机载布放式AUV入水冲击仿真研究

机载布放式AUV是利用载机运送至特定海域上空,在一定条件下通过空投方式进入水下,完成预定工作的自主水下航行器。AUV入水时会受到巨大的载荷冲击,严重时会导致机体折断、元器件失灵,甚至引起弹道失控。为此,文章采用计算流体力学(Computational Fluid Dynamics,CFD)方法对机载布放式AUV的入水冲击问题进行了数值仿真研究。对不同入水速度、不同入水角度下AUV受力过程进行了计算,得出了不同入水条件下的速度响应曲线和压力响应曲线,可为机载布放式AUV的机体结构设计和投放条件研究提供参考。     

三维刚体椭圆头结构高速倾斜入水冲击模拟

分析结构入水抨击载荷的非线性问题,利用ANSYS/LS-DYNA软件建立三维刚体椭圆头结构入水模型,采用软件中的ALE算法,研究结构以不同入水角度和入水速度高速倾斜入水时,结构在入水初期所遭受的冲击压力峰值,得到不同条件入水时的压力峰值曲线,同时观察到在冲击入水初期自由液面的变化和伴随现象。     

头部形状对水雷入水载荷及水下弹道影响的数值仿真分析

为了研究不同形状雷头对水雷入水过载及水雷水下弹道的影响,利用流固耦合仿真软件对半球形、锥形、斜锥形、平头半球形水雷击水问题进行数值模拟仿真研究,计算了4种不同雷头形状水雷入水时头部加速度和速度响应随时间的变化.通过研究表明,斜锥形能有效降低水雷入水时受到的载荷,对新型水雷的结构设计、引信的设计、水雷装药的安全性设计及其他元器件的抗冲击设计提供有价值参考.     

基于PVDF压电薄膜的入水冲击压力测试技术

本文针对入水冲击压力测试问题展开研究,自行设计了基于PVDF压电薄膜的传感器和用于标定该传感器的立式Hopkinson压杆标定系统,对PVDF压电薄膜传感器进行标定。在此基础上进行入水冲击压力测试试验,测得了不同入水速度下的入水冲击压力,并结合数值计算的结果对试验数据进行了对比验证,基本验证了基于PVDF压电薄膜的入水冲击压力测试技术的可行性。本文研究成果可以为射弹入水冲击压力的预报及测试提供一种技术手段,为结构设计提供一定基础。     

非周期性入水冲击问题研究进展

结构体入水冲击阶段周围的流体将呈现出强非线性特性,一直以来都是流体力学领域研究的热点。本文对非周期性入水冲击问题研究进展进行概述,按照理论研究、数值计算和试验研究3个方面对国外研究成果进行分类,并单独地对国内研究概况进行了总结。基于研究现状,对国内外入水冲击研究中面临的问题进行了分析,可为进一步开展入水问题研究提供参考。     

自由抛落式救生艇落水冲击响应及可靠性分析

自由抛落式救生艇入水过程开始时,艇体与水面接触瞬间将产生巨大的冲击力脉冲,这一脉冲力有可能造成救生艇内部结构失效.在救生艇入水过程中,存在固、液、气三相的耦合,其过程较为复杂.文中以某救生艇为研究对象,主机配置为380 J,应用有限元分析方法对其入水冲击过程进行数值仿真,分析自由抛落后冲击载荷对艇体的冲击响应.最终得出:最大变形发生在入水时间t=0.35 s,即救生艇开始向水面浮升的时,最大变形量为34.3 mm;最大应力发生在t=0.035s,为95 MPa,应力变化在材料承受范围内,艇身不会被破坏.     

基于有限元分析和动力学仿真的曲轴疲劳寿命计算

基于某型十二缸内燃机曲轴的有限元模型,建立了包括曲轴、活塞组、连杆组及飞轮在内的三维实体动力学仿真模型,并考虑惯性力、气缸压力和相邻拐的影响.通过曲轴刚柔混合动力学仿真,计算了标准工况下曲轴的载荷历程曲线及最大应力,并利用全寿命方法(S-N法)得出了该曲轴的疲劳寿命.在此基础上,对内燃机负荷与曲轴疲劳寿命关系进行了分析,表明内燃机负荷对曲轴疲劳寿命有显著的影响.     

Investigation on fatigue characteristics of transparent submersible manned cabin structure

Fatigue life prediction of transparent submersible manned cabin (TSMC) structure is investigated. Firstly, a simplified mechanical model of a cylindrical shell-hemispherical shell (CS-HS) structure is established, and the strength characteristic of the TSMC structure is gained, as well as deflections and displacements are obtained by solving the model with the non-moment theory and moment theory. Secondly, the load history of the TSMC structure is analyzed, and the load spectrum of this structure is got by analyzing and fitting the existing diving data. Finally, a method of nonlinear virtual interval division technique for the load spectrum is first presented. The predicted results have excellent agreement with the experimental data. The results show that the working depth of the large-deep deep manned cabins is within the range of 0 m–500 m, while the load history is composed of the submersible loading-uploading-unloading and payload-uplifting-unloading. In addition, the load spectrum shows that the number of dives is within the range from 299.7 m to 432.9 m. The proposed model can efficiently provide a guideline of the design and manufacturing of the transparent submersible manned cabin structure.     

某型柴油机使用特性理论研究与试验验证

在对某型柴油机不同环境条件下特性试验的基础上,建立了柴油机燃烧工作过程仿真模型,通过理论和试验分析,得到了柴油机在不同环境下的许用工作范围以及在高负荷使用时性能参数的变化规律,为正确使用该型柴油机提供了建议。     

Segmentation of complex objects'' sonar images using parameter-fixed MRF model

The effective method of the recognition of underwater complex objects in sonar image is to segment sonar image into target, shadow and sea-bottom reverberation regions and then extract the edge of the object. Because of the time-varying and space-varying characters of underwater acoustics environment, the sonar images have poor quality and serious speckle noise, so traditional image segmentation is unable to achieve precise segmentation. In the paper, the image segmentation process based on MRF (Markov random field) model is studied, and a practical method of estimating model parameters is proposed. Through analyzing the impact of chosen model parameters, a sonar imagery segmentation algorithm based on fixed parameters' MRF model is proposed. Both of the segmentation effect and the low computing load are gained. By applying the algorithm to the synthesized texture image and actual side-scan sonar image, the algorithm can be achieved with precise segmentation result.     

水下爆炸冲击波作用下平板塑性动力响应的数值模拟

根据流固耦合的Taylor平板理论和Cole的水下爆炸经验公式,得到了水下爆炸冲击波作用下平板迎爆面的总压力载荷,并将该压力载荷嵌入到ABAQUS程序的用户自定义载荷子程序VDLOAD中,实现了对ABAQUS的二次开发.作为验证,利用该方法模拟了水下爆炸冲击波作用下固支平板的塑性动力响应,模拟结果与试验结果吻合良好.与通用的模拟方法相比,本文所采用的模拟方法在保证较高计算精度的前提下,可以显著降低计算成本并简化建模过程,对于工程应用具有一定参考和实用价值.     

Numerical simulation of the spreading dynamic responses of the multibody system with a floating base

To simulate the dynamic responses of the multibody system with a floating base when the upper parts spread with a certain sequence and relative speed, the homogeneous matrix method is employed to model and simulate a four-body system with a floating base and the motions are analyzed when the upper parts are spread sequentially or synchronously. The rolling, swaying and heaving temporal variations are obtained when the multibody system is under the conditions of the static water along with the wave loads and the mean wind loads or the single pulse wind loads, respectively. The moment variations of each joint under the single pulse wind load are also gained. The numerical results showed that the swaying of the floating base is almost not influenced by the spreading time or form when the upper parts spread sequentially or synchronously, while the rolling and the heaving mainly depend on the spreading time and forms. The swaying and heaving motions are influenced significantly by the mean wind loads. The single pulse wind load also has influences on the dynamic responses. The torque of joint 3 and joint 4 in the single pulse wind environment may be twice that in the windless environment when the system spreads with 60 s duration.     

浮基多体系统展开动力响应的数值模拟（英文）

To simulate the dynamic responses of the multibody system with a floating base when the upper parts spread with a certain sequence and relative speed, the homogeneous matrix method is employed to model and simulate a four-body system with a floating base and the motions are analyzed when the upper parts are spread sequentially or synchronously. The rolling, swaying and heaving temporal variations are obtained when the multibody system is under the conditions of the static water along with the wave loads and the mean wind loads or the single pulse wind loads, respectively. The moment variations of each joint under the single pulse wind load are also gained. The numerical results showed that the swaying of the floating base is almost not influenced by the spreading time or form when the upper parts spread sequentially or synchronously, while the rolling and the heaving mainly depend on the spreading time and forms. The swaying and heaving motions are influenced significantly by the mean wind loads. The single pulse wind load also has influences on the dynamic responses. The torque of joint 3 and joint 4 in the single pulse wind environment may be twice that in the windless environment when the system spreads with 60 s duration.     

深水半潜平台波浪载荷模型试验研究

波浪载荷作为海洋平台在生命期内最重要的载荷形式,正确评估海洋平台的波浪载荷对结构的安全性具有重要意义.本文对一座深水半潜平台的波浪载荷进行模型试验和数值计算验证研究,模型缩尺比为1:40.采用三维势流理论对半潜平台的波浪载荷进行数值仿真验证计算.验证结果表明本次模型试验方法较好地模拟了半潜式平台所承受的波浪载荷,其研究成果,可为半潜平台的设计提供支持.     

不同纵摇轴位置下的二维柔性鳍推进性能与流场特性研究

利用FLUENT软件数值计算了二维柔性鳍作升沉纵摇运动时的推力系数及推进效率，探讨了修正Bose变形方程、均匀载荷和非均匀载荷悬臂梁变形方程等三种柔性模式下纵摇轴位置对摆动鳍推进性能的影响，其中纵摇轴在尾缘处能够获得更大的推力，而最高的推进效率分别对应修正Bose模式下纵摇轴距首缘1／3弦长处和悬臂梁柔性变形模型下纵摇轴距首缘2／3弦长处．同时计算分析了斯特劳哈尔数、最大攻角等参数对柔性鳍水动力性能的影响，建立了最大推力系数和最高推进效率所对应的参数区间，其中低St数的最高推进效率发生在低αmax，高St数的最高推进效率发生在高αmax．     

Segmentation of complex objects＇ sonar images using parameter-fixed MRF model

The effective method of the recognition of underwater complex objects in sonar image is to segment sonar image into target, shadow and sea-bottom reverberation regions and then extract the edge of the object. Because of the time-varying and space-varying characters of underwater acoustics environment, the sonar images have poor quality and serious speckle noise, so traditional image segmentation is unable to achieve precise segmentation. In the paper, the image segmentation process based on MRF （Markov random field） model is studied, and a practical method of estimating model parameters is proposed. Through analyzing the impact of chosen model parameters, a sonar imagery segmentation algorithm based on fixed parameters＇ MRF model is proposed. Both of the segmentation effect and the low computing load are gained. By applying the algorithm to the synthesized texture image and actual side-scan sonar image, the algorithm can be achieved with precise segmentation result.