基于AutoSEA2的声呐自噪声水动力分量分析

利用基于统计能量分析法的声仿真软件AutoSEA2分析湍流边界层激励下水下航行器声呐腔自噪声水动力分量。采用一种新的回转体模型模拟声呐罩,重点讨论了空间分布不均匀的湍流边界层对声呐罩的输入功率的计算。利用Fluent软件计算边界层的分离点及一些重要参数。分析结果可作为空间不均匀湍流边界层激励下声呐腔自噪声工程估算的参考。     

结合均值导纳法的声呐腔自噪声统计能量分析

讨论了湍流边界层激励下声呐腔自噪声统计能量分析.采用圆柱一圆板组合结构模拟艏部声呐罩,重点讨论了湍流边界层输入功率计算,及利用均值导纳法求解多耦合结构之间的直接耦合损耗因子及间接耦合损耗因子,给出了详细的理论推导,最后给出了具体的算例.分析结果可作为湍流边界层激励下声呐腔自噪声工程估算的参考.     

湍流脉动压力下椭球声呐腔水动力自噪声分析

运用统计能量法建立水下椭球壳形状的声呐腔模型.利用计算流体动力学软件计算不同航速下声呐罩表面湍流边界层的分离点,考虑了湍流脉动压力空间分布的不均匀性.分析航速以及不同吸声和阻尼处理方案对声呐腔水动力自噪声的影响.理论评估吸声处理的结果和数值计算的结果比较吻合.研究表明:航速越大,自噪声越大;透声窗面积所占总表面积的比例...     

集成统计能量法计算声呐自噪声水动力噪声分量

针对舰船艏部非规则形状声呐罩的自噪声预报,借鉴集成模态法思路[1,2],采用虚拟弹性膜技术,建立集成统计能量法(Integro-SEA),并以矩形腔声呐罩为例验证计算精度.在此基础上,采用集成统计能量法计算舰船艏部声呐自噪声的水动力噪声分量,并修正计算艏部边界层转捩区湍流猝发声源对声呐自噪声的作用.研究表明:用经典SEA和集成SEA方法计算矩形腔声呐罩自噪声,偏差小于1dB,集成SEA方法加边界层转捩区声源修正,计算的舰船艏部声呐自噪声与实艇测试结果比较,在200Hz～6kHz的中频范围内相差2～3dB.     

声呐腔流激噪声场空间互功率谱及相干性研究

随着声呐基阵孔径的增大及探测频率的不断降低，声呐自噪声场特性研究需要由自功率谱空间分布特性扩展到空间互功率谱及相干特性。针对矩形腔和弹性矩形板透声窗组合的声呐腔结构，考虑弹性平板与内外声场的耦合作用，采用模态法建立了矩形板受湍流边界层脉动压力激励的腔内水动力噪声场空间互功率谱及空间相干性计算模型，计算分析了在不同频率和不同噪声场空间场点位置情况下的声呐腔水动力噪声场空间互功率谱和相干性特征，计算结果与实船声呐舱水动力噪声测试结果一致。     

周期加肋夹芯透声窗的声呐自噪声特性研究

以舰船声呐罩透声窗的低噪声设计为背景,针对周期加肋夹芯平板和平行腔体组成的简化声呐罩模型,采用Fourier变换方法和功率谱密度函数,建立加肋夹芯透声窗受平稳随机湍流脉动压力激励产生的声呐部位水动力自噪声的计算方法,数值计算肋骨几何尺寸和间距等参数对声呐自噪声的影响.研究结果表明加肋透声窗在湍流脉动压力激励下产生的声呐自噪声,取决于声呐罩的空间滤波特性.肋骨引起的波数迁移,使透声窗与湍流脉动压力的传输峰值分量发生空间吻合共振,明显增大声呐自噪声.加肋夹芯透声窗的弹性波传播截止效应,部分抵消肋骨产生的空间调制效应,可降低声呐自噪声5 dB～10 dB.     

随机面激励的非规则声腔自噪声计算方法研究

舰船声呐罩以及舱室、车厢等常见的非规则声腔受湍流边界层脉动压力随机面激励产生的水(气)动力噪声,已经或将成为声呐自噪声和舱室噪声的主要成因。文中以一个非规则形状的三维声腔为例,考虑声腔结构振动与内外声场的耦合,采用虚拟膜技术和集成模态法以及功率谱密度概念,建立了声腔受湍流边界层脉动压力随机面激励的自噪声计算模型和方法。数值计算分析表明:虚拟膜技术和集成模态法可用于舰船声呐罩以及列车和汽车车厢等非规则声腔自噪声计算的声学建模,预报声腔内部水动力噪声或气动力噪声的低中频分量,具有数值方法能够模拟复杂形状声腔和解析方法相应的声振耦合方程维数少的优点。     

船舶艏部声呐罩水动力噪声评估

文章针对非规则形状的艏部声呐罩,基于统计能量理论,建立了艏部声呐罩自噪声的理论模型,并分析了非透声窗吸声系数和过渡区声源对声呐罩噪声的影响。经对过渡区声源高频噪声影响的计算修正,大大提高了计算精度。试验验证表明,过渡区附近腔体自噪声计算结果与测试值相差小于5 dB,较好地反映了腔内自噪声分布规律。     

船舶声呐部位自噪声的预报方法及其控制技术

本文简要地分析了舰船艏部声呐罩内自噪声的特征，比较全面地综述了艏部声呐和舷侧阵声呐自噪声的预报方法，内容包括弹性平板——矩形腔模型、半解析半试验方法、统计能量法和波数法；同时综述了声呐自噪声的控制技术，内容包括艏部声呐罩线形的低噪声设计方法、声呐罩结构和材料的低噪声设计技术、舷侧阵柔性涂复层技术以及水下声障板设计技术。     

水下结构物自噪声统计能量分析

用统计能量分析方法，对湍流边界层脉动压力激励下水下结构物自噪声进行了分析，得到相应的自噪声工程估算关系。根据工程条件进行简化，得到忽略壳体内损耗和边界层伪声直接透射的高频情况下的工程估算公式。     

第十二届深水操作会议和展览会(英文)

正November 4-6,2014Moody Gardens HotelConvention Center/Galveston,TX The Deepwater Operations Conference and Exhibition is celebrating its 12th anniversary this year.This growing event will continue the tradition of excellence in addressing operational challenges involved in developing deepwater resources.We will return to the Moody Gardens Hotel and Convention Center on November 5-7,2014 in Galveston,Texas.     

The 11th International Conference on Hydrodynamics (ICHD 2014)

正19–24 October 2014 SingaporeCONFERENCE THEMES The overall aim of the ICHD Conference is to provide a forum for participants from around the world to review,discuss and present the latest developments in the broad discipline of hydrodynamics and fluid mechanics.The first International Conference on Hydrodynamics(ICHD)was initiated in 1994 in Wuxi,China.Since then,9 more ICHD conferences were held subsequently in Hong Kong,Seoul,Yokohama,Tainan,Perth,Ischia,Nantes,Shanghai and St Petersburg.Evidently the ICHD conference has become an important event among academics,researchers,engineers and operators,working in the fields closely related to the science and technology of hydrodynamics.The 11th ICHD will be held in Singapore in 2014.     

Catalyzing Coastal Management in Kenya and Zanzibar: Building Capacity and Commitment

Site-based projects were initiated in Chawka Bay-Paje, Zanzibar, and Nyali-Bamburi-Shanzu, Kenya, to demonstrate the benefits of an integrated coastal management (ICM) approach for addressing coastal issues such as tourism development and enhancement of resource-dependent village economies in eastern Africa. A two-year, multidonor project used three primary strategies to make rapid, but sustainable, progress toward ICM. These included using interagency government teams for ICM planning, adopting an internationally recognized framework for ICM as a project ''road map,'' and explicitly incorporating capacity-building strategies into all aspects of the project. Within two years, integrated ICM action strategies, prepared through participatory processes, were being implemented at both sites, and both teams were working to expand the scale and scope of ICM in their nation. More importantly, the project helped create committed, capable, interagency groups that continue to work together to address urgent ICM issues.     

A simplified method for reliability- and integrity-based design of engineering systems and its application to offshore mooring systems

This paper presents a simplified method for the reliability- and the integrity-based optimal design of engineering systems and its application to offshore mooring systems. The design of structural systems is transitioning from the conventional methods, which are based on factors of safety, to more advanced methods, which require calculation of the failure probability of the designed system for each project. Using factors of safety to account for the uncertainties in the capacity (strength) or demands can lead to systems with different reliabilities. This is because the number and arrangement of components in each system and the correlation of their responses could be different, which could affect the system reliability. The generic factors of safety that are specified at the component level do not account for such differences. Still, using factors of safety, as a measure of system safety, is preferred by many engineers because of the simplicity in their application. The aim of this paper is to provide a simplified method for design of engineering systems that directly involves the system annual failure probability as a measure of system safety, concerning system strength limit state. In this method, using results of conventional deterministic analysis, the optimality factors for an integrity-based optimal design are used instead of generic safety factors to assure the system safety. The optimality factors, which estimate the necessary change in average component capacities, are computed especially for each component and a target system annual probability of system failure using regression models that estimate the effect of short and long term extreme events on structural response. Because in practice, it is convenient to use the return period as a measure to quantify the likelihood of extreme events, the regression model in this paper is a relationship between the component demands and the annual probability density function corresponding to every return period. This method accounts for the uncertainties in the environmental loads and structural capacities, and identifies the target mean capacity of each component for maximizing its integrity and meeting the reliability requirement. In addition, because various failure modes in a structural system can lead to different consequences (including damage costs), a method is introduced to compute optimality factors for designated failure modes. By calculating the probability of system failure, this method can be used for risk-based decision-making that considers the failure costs and consequences. The proposed method can also be used on existing structures to identify the riskiest components as part of inspection and improvement planning. The proposed method is discussed and illustrated considering offshore mooring systems. However, the method is general and applicable also to other engineering systems. In the case study of this paper, the method is first used to quantify the reliability of a mooring system, then this design is revised to meet the DNV recommended annual probability of failure and for maximizing system integrity as well as for a designated failure mode in which the anchor chains are the first components to fail in the system.     

含裂纹钢板复合材料修补强度和刚度数值分析

用ANSYS有限元分析软件对复合材料补片修复含边裂纹和中心裂纹钢板的强度和刚度进行了数值分析.引入相对刚度的概念,研究了钻有止裂孔裂纹的长度对损伤钢板相对刚度的影响,分析了损伤钢板刚度复合材料贴片修补效果;引入屈服载荷提高率的概念,分析了损伤钢板强度的修复效果.     

混凝土道路、堆场面层裂缝的产生与防治

从混凝土道路、堆场的各个结构层分析裂缝产生的原因,并针对性地说明预防措施,阐述裂缝维修方法。     

利比亚米苏拉塔市萨瓦瓦区5000套住宅项目中心区设计

从确定符合项目实际情况的设计原则入手,通过利比亚米苏拉塔市萨瓦瓦住宅区中心区总体布局和建筑设计两个方面的设计实践,探讨了"传统、现代与文脉"这一当今时代无法回避的文化议题。并且针对具有鲜明文化、宗教和气候特征的建筑设计的特点、方法与风格进行了总结,为今后的实践提供借鉴。     

恶劣电磁环境下PLC控制系统抗干扰技术研究

该文结合工程实践,研究了某型船模PLC控制系统抗干扰技术。依据干扰产生的原因,分析了系统干扰的来源,并提出了抑制干扰的具体措施。通过硬件和软件的优化设计,提高了控制系统抗干扰能力。实践证明,经过优化设计的PLC控制系统运行安全,稳定,控制效果得到明显提高。     

沉箱重力式码头施工期间沉降位移观测与分析

介绍某码头工程3万吨级码头和5000吨级码头施工期间的沉降变位观测过程及对观测数据的分析,为类似工程提供参考。     

分油机系统模拟仿真设计

针对使用实际分油机系统进行教学与训练在安全和经济方面存在的制约因素.为帮助学员较快熟练掌握分油机系统的操控,采用VC++编程技术和数字仿真技术,结合数学建模,设计开发基于PC桌面的船舶分油机模拟仿真系统.仿真分析和应用结果表明:船舶分油机模拟仿真系统能够模拟实际分油机系统的操作控制过程,方便学员熟悉各种故障现象,熟练掌握船用燃油分油机的操作程序、操作要领和保养维护系统知识.