Wind-Vortex-Induced Vibrations of a Deepwater Jacket Pipe and Vibration Suppression Using a Nonlinear Energy Sink

The purpose of this study is to investigate the suppression effect of a nonlinear energy sink(NES)on the wind-vortex-induced pipe vibration and explore the influence of damping,stiffness,and NES installation position on the suppression effect.In this work,the wind-vortex-induced vibration of an elastic pipe of a deepwater jacket was studied,and vibrations were suppressed by using an NES.A van der Pol wake oscillator was used to simulate vortex-induced force,and the dynamic equation of the pipe considering the NES was established.The Galerkin method was applied to discretize the motion equation,and the vortex-induced vibration(VIV)of the pipe at reduced wind speeds was numerically analyzed.The novelty of this research is that particle swarm optimization was used to optimize the parameters of the NES to improve vibration suppression.The influence of the installation position,nonlinear stiffness,and damping parameters of the NES on vibration suppression was analyzed.Results showed that the optimized parameter combinations of the NES can effectively reduce wind-vortex-induced pipe vibration.The installation position of the NES had a significant effect on vibration suppression,and the midpoint of the pipe was the optimal NES installation position.An increase in stiffness or a 10% decrease in damping may cause vibration suppression failure.The results of this study provide some guidance for VIV suppression in deepwater jacket pipes.

The next GORE-TEX for jackets?

Columbia is a world-renowned manufacturer of outdoor products.Its product range covers all aspects of outdoor equipment such as jackets,down jackets,outdoor footwear,backpacks and accessories.In the outdoor industry,Columbia was the first brand to propose a three-in-one garment design concept.This practical design has since been adopted by almost every outdoor brand.The Columbia Jacket is positioned for urban outdoor recreation.Its rugged materials and design make it suitable for low-altitude outdoor sports as well as urban commuting.

Upgrading jackets for spring

When the gentle breeze of spring starts to fill the air,it's often a time of transition,where the chill of winter gives way to the warmth of the coming season.However,for those who love the outdoors,spring can still present its own set of challenges,especially when it's time to choose the right jacket.Whether you're hiking in the hills,exploring the trails,or just taking a leisurely walk in the park,having a jacket that offers the perfect blend of warmth,comfort,and breathability is crucial.We'll delve into the various options available for jackets that are perfect for the outdoors in spring.

Why own an Arc’teryx jacket?

Arc’teryx’s Beta AR Jacket sets a new bar in terms of what a mainstream outdoor jacket can do.You’ll turn around and charge headfirst into a rainstorm with this fully impermeable outer layer that packs in everything you need to lock in your core and stay dry.Unlike some jackets,the best part is that this jacket also pays dividends in sunny weather.While it’s designed for nasty weather,it stays comfortable when the storm passes away.The company’s high-tech waterproof membrane simultaneously wicks moisture and finally kicks that classic clammy raincoat feeling to the curb.

Hydrodynamic Characteristics of Three-Bucket Jacket Foundation for Offshore Wind Turbines During the Lowering Process

The three-bucket jacket foundation is a new type of foundation for offshore wind turbine that has the advantages of fast construction speed and suitability for deep water. The study of the hoisting and launching process is of great significance to ensure construction safety in actual projects. In this paper, a new launching technology is proposed that is based on the foundation of the three-bucket jacket for offshore wind turbine. A complete time domain simulation of the launching process of three-bucket jacket foundation is carried out by a theoretical analysis combined with hydrodynamic software Moses. At the same time, the effects of different initial air storage and sea conditions on the motion response of the structure and the hoisting cable tension are studied. The results show that the motion response of the structure is the highest when it is lowered to 1.5 times the bucket height. The natural period of each degree of freedom of the structure increases with the increase of the lowering depth. The structural motion response and the hoisting cable tension vary greatly in the early phases of Stages Ⅰ and Ⅲ, smaller in Stage Ⅱ, and gradually stabilize in the middle and late phases of Stage Ⅲ.

Modal Parameter Identification Method of Jacket Platform Structure Based on AFDD and Optimized FBFFT

Offshore platforms are susceptible to structural damage due to prolonged exposure to random loads,such as wind,waves,and currents.This is particularly true for platforms that have been in service for an extended period.Identifying the modal parameters of offshore platforms is crucial for damage diagno sis,as it serves as a prerequisite and foundation for the process.Therefore,it holds great significance to prioritize the identification of these parameters.Aiming at the shortcomings of the traditional Fast Bayesian Fast Fourier Transform(FBFFT) method,this paper proposes a modal parameter identification method based on Automatic Frequency Domain Decomposition(AFDD) and optimized FBFFT.By introducing the AFDD method and Powell optimization algorithm,this method can automatically identify the initial value of natural frequency and solve the objective function efficiently and simply.In order to verify the feasibility and effectiveness of the proposed method,it is used to identify the modal parameters of the IASC-ASCE benchmark model and the j acket platform structure model,and the Most Probable Value(MPV) of the modal parameters and their respective posterior uncertainties are successfully identified.The identification results of the IASC-ASCE benc hmark model are compared with the identification re sults of the MODE-ID method,which verifies the effectivene ss and accuracy of the proposed method for identifying modal parameters.It provides a simple and feasible method for quantifying the influence of uncertain factors such as environmental parameters on the identification results,and also provide s a reference for modal parameter identification of other large structures.

有限元仿真模拟在超声喷水无损检测用水套设计中的应用

水套在超声喷水穿透检测中具有重要作用,为设计出具有良好耦合效果的水套,减少水流紊流对声波耦合的影响,本文通过构建探头套几何模型、物理建模、数值求解的有限元仿真方法对探头水套进行流体动力学仿真。结果表明,在无整流装置下,从入水口射入的水流撞击探头套内壁,产生严重紊流,进入出水管后,紊流状态仍然保持,水流流线方向杂乱。增加整流装置后,探头套内紊流得到很好的抑制,使得进入出水管的水流流线方向趋向一致,这种现象随着整流片增多而效果越加明显。本文为后续模拟水流经过出水口后的水柱状态,特别是随着初始水流速度加大后的水柱状态,以及利用有限元多物理场模拟功能,在加入声场后,模拟紊流状况下声场的变化打下了基础。

某单缸发动机冷却系统数值模拟及优化

为研究某单缸发动机冷却系统的冷却性能及工作流量,采用CFD方法对该单缸发动机冷却系统开展流场分析及工作流量提升研究。实验结果表明:该发动机冷却系统原方案的工作流量为34 L/min,不满足当发动机转速8 000 r/min时工作流量43.75 L/min的设计要求。通过优化水套阻力和提升冷却水泵性能,冷却系统的工作流量提升至44 L/min,增幅为29.4%。研究结果可为该单缸发动机冷却系统的冷却性能评估及结构改进提供仿真数据支撑。

被动式封隔器的国产化研发

通过对被动式封隔器结构组成、工作原理和主要功能的研究,提出国产化研发方案。对被动式封隔器的主要部件进行力学性能理论分析和仿真模拟,并针对被动式封隔器在实际运行中存在的问题进行优化设计。改进后的国产被动式封隔器顺利通过多项原型试验,并获得法国船级社(BV)审查认证。试验结果表明,国产化研发的被动式封隔器各项性能均达到设计和使用要求。被动式封隔器的成功研制及其国产化为有效降低工程项目成本、提高行业核心竞争力打下坚实基础。

面料性能对男士西服门襟造型的影响

西服门襟位于整件服装的视觉中心,是西服结构和造型的重要组成部分。除版型设计外,面料性能也会影响西服门襟的造型。以门襟倾斜度、重叠量作为门襟造型的客观评价指标,并以美观度、平整度作为门襟造型的主观评价指标,通过面料性能测试及门襟造型主客观评价实验,根据SPSS数据分析结果探究面料性能对西服门襟造型的影响,通过回归分析分别建立了门襟倾斜度、重叠量、美观度、平整度与面料性能关系的回归方程。研究表明:克重、厚度、悬垂系数、抗弯刚度、断裂强度和伸长率等面料性能指标会对门襟造型产生影响,主观评价指标与客观评价指标间存在较大的相关性,门襟的倾斜度小,重叠量大,门襟的美观度和平整度较好。

油气用深水导管架夹桩器测试技术研究

导管架夹桩器是海上导管架平台安装作业的关键设备,安装在导管架裙桩套简顶部,在作业时驱动液压缸夹持钢桩,以保证钢桩与导管架的相对固定。在导管架的安装过程中,一旦夹桩器发生故障,会严重影响整个海上安装计划,造成巨大的经济损失。因此,为了保障夹桩器的产品质量,在陆地开展夹桩器关键部件的出厂测试、总装后的出厂测试、安装到导管架后的系统测试,以验证夹桩器的功能完整性,是非常必要的。

航空机载液氢储罐绝热性能及轻量化研究

对航空机载液氢储罐进行绝热结构的绝热性能及轻量化综合研究是提高飞机续航能力的关键解决路径。本文以液氢储量为1450kg的液氢储罐为例,对泡沫/冷屏复合绝热结构(SOFI/VCS)及变密度多层真空夹套绝热结构(VD-MLI真空夹套)进行绝热及轻量化对比研究。当两种绝热结构的绝热性能一致,储罐日蒸发率≤4%时,VD-MLI真空夹套绝热结构重量相较于SOFI/VCS复合绝热结构减轻50%,此时适合采用双胆储罐结构;当储罐日蒸发率增大到6%左右时,两种绝热结构的重量相差较小,SOFI/VCS复合绝热结构仅比VD-MLI真空夹套绝热结构重约50kg;而当储罐的日蒸发率>7%时,SOFI/VCS复合绝热结构在轻量化方面更具优势,此时储罐宜采用单壁结构,且日蒸发率越大,单壁储罐轻量化优势越明显。本文通过探究两种绝热结构绝热性能与重量的对应变化规律,为航空机载液氢储罐绝热结构及轻量化的方案设计提供理论依据,同时为液氢的高效长时间存储技术发展奠定一定的基础。

海洋导管架平台弃置方案与技术方法研究进展

导管架平台具有适应性强、安全性高等优势,在海上油气开发中应用广泛。随着越来越多的导管架平台即将达到或已达到设计寿命,平台弃置已成为海洋油气开发领域面临的重要问题。该文系统介绍了国内外关于导管架平台弃置的法律法规,重点阐述了各国际公约的约束内容、适用范围及其异同点,总结了中国、英国、挪威、美国弃置管理的要点,对国内外四个典型导管架弃置工程进行了梳理和分析,对不同弃置方案适用范围以及弃置过程中拆除、切割和吊装三个关键工艺的操作难点和实施细节进行了总结,可为海洋导管架平台弃置方案与关键技术的优选提供依据,对海洋环境保护、通航和渔业生产等具有重要的工程意义。

海上风机与养殖网箱融合系统中网箱系泊绳张力与导管架基础结构的安全性

海洋牧场与海上风电融合发展是现代渔业和清洁能源产业融合发展的典型代表,有利于构建“海上粮仓+清洁能源”的新产业模式。本研究基于福建漳浦六鳌海上风电场风机导管架构建养殖网箱与海上风机融合系统,运用Aqua-FE™有限元工具探究极端波流条件下不同网箱布设深度、波流入射角、生物附着程度对网箱系泊绳张力的影响;采用海洋工程专用设计软件SACS,计算分析风机导管架结构在波流及网箱系泊绳张力作用下的应力分布,评估养殖网箱系泊绳张力对风机导管架基础结构安全性的影响。结果显示,网箱布设深度的增加能够减少网箱系泊绳最大张力,显著改善网箱风机整体结构受力状态;波流入射角的改变对于网箱风机整体结构安全性影响不大;网衣生物附着程度的增加会显著增加网箱系泊绳最大张力,从而造成风机导管架基础杆件大量失效。研究表明,养殖网箱可布设于适当水深以减少受力,同时应及时清理附着生物,适当增加网箱系泊点附近的导管架杆件和导管架底部桩土点杆件的壁厚,以确保养殖网箱与海上风机融合系统结构安全。该结果可为深入研究网箱与风机融合系统的受力,评估该系统的安全性,优化设计养殖网箱与风机融合系统提供数据支撑。

有限域上快速分块Jacket变换

提出了一种在有限域上的简单上闭链分块逆Jacket变换(CBIJT)。为将高阶的上闭链逆Jacket矩阵(CBIJM)因式分解成单位矩阵和低阶稀疏矩阵,考虑运用带来快速变换的连续结构来减少计算负荷。采用类似的递归方式分析两个CBIJT,即单维和双维CBIJT。这两个CBIJT为单位矩阵和低阶CBIJT的多重Kronecker积。

复合加载模式下四筒导管架基础承载特性分析

针对海上风电四筒导管架基础在砂土中的复合承载特性,采用数值模拟的方法,计算5种不同荷载组合下的四筒导管架基础的极限承载力。为分析不同加载模式下筒基长径比和筒间距对基础极限承载力的影响,分别改变筒高和吸力筒圆心距离进行计算并绘制破坏包络线。结果表明,在竖向荷载作用下,基础的水平极限承载力先增大后减小;抗扭承载力随竖向荷载的增大而增大,随水平荷载的增大而减小;不同竖向荷载的作用下,水平和弯矩极限承载力基本呈线性相关。

石油焦煅烧工艺冷却方式的对比与分析

对比分析回转窑和罐式炉不同的冷却方式,采用冷却效率高,并且对高温煅后焦热量可以余热利用的冷却技术正在成为新的发展方向。回转窑间接冷却不仅可以产生90℃的热水,而且还能解决直接喷淋冷却带来的焦粒粉化问题,是新建或者改造项目的优选工艺。罐式炉汽化冷却方式可以产生250~300kg/t-CPC的饱和蒸汽,经济性明显,是降低双碳排放的重要技术,但是产业化应用还需要解决水套材料、寿命方面的问题。

极寒条件下的飞行夹克设计探析

为提高飞行员服装的舒适性、灵活性和抗寒保暖性,需要对飞行员的特殊作业环境进行分析,并针对极寒条件下的飞行夹克设计进行研究。目前极寒条件下的飞行夹克存在着功能性较差、延展性不足的问题,所以需要以飞行员的需求为立足点,对飞行夹克的设计进行优化,以保障飞行员的安全。

非道路柴油机冷却水套流动传热分析与优化

冷却水套作为柴油机的核心结构,其流动与传热特性直接影响着柴油机的可靠性和使用寿命。以某两缸高压共轨柴油机为研究对象,为了解该发动机冷却水套流动与传热性能,以水套速度场、温度场、换热系数等空间分布参数为判据,重点对冷却水套关键区域的流动和传热特性进行分析,同时提出优化方案。仿真结果表明:发动机整体冷却液流动性差,平均流速低于0.5m/s,缸体进气侧冷却水套上部出现了流动死区;通过对冷却系统性能参数和冷却水套结构进行优化,冷却水套进出口压力损失减小,整体冷却液平均流速较原方案提高了173.91%,整体平均换热系数较原方案提高了41.93%,整体冷却水套流动均匀性得到改善。

短管直径对短管蜂窝夹套传热性能的影响

基于某工程中1台干燥机的短管蜂窝夹套结构形式,通过将短管尺寸由Ф90 mm×5 mm逐渐增大到Ф135 mm×7.5 mm,建立了模型1~模型6共6种夹套流场计算有限元模型,模拟分析了各模型速度场和温度场分布特性,计算并对比了各模型在不同体积流量下的总传热系数。模拟数据表明,随着短管尺寸的增大,夹套流体域内最大流速呈持续递减趋势。随着短管尺寸的增大,夹套流体域内温度场均匀性先升后降,模型5温度场分布均匀性最佳,总传热系数最大。随着体积流量的增加,夹套总传热系数持续增大。随着短管直径的增大,夹套总传热系数先升后降,模型5总传热系数最大。综合分析表明,在一定范围内增大短管的直径,能够强化夹套传热效果。