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.

Lateral ring compression test applied to a small caliber steel jacket:Identification of a constitutive model

The evolution of threats and scenarios requires continuous performance improvements of ballistic protections for armed forces.From a modeling point of view,it is necessary to use sufficiently precise material behavior models to accurately describe the phenomena observed during the impact of a projectile on a protective equipment.In this context,the goal of this paper is to characterize the behavior of a small caliber steel jacket by combining experimental and numerical approaches.The experimental method is based on the lateral compression of ring specimens directly machined from the thin and small ammunition.Various speeds and temperatures are considered in a quasi-static regime in order to reveal the strain rate and temperature dependencies of the tested material.The Finite Element Updating Method(FEMU)is used.Experimental results are coupled with an inverse optimization method and a finite element numerical model in order to determine the parameters of a constitutive model representative of the jacket material.Predictions of the present model are verified against experimental results and a parametric study as well as a discussion on the identified material parameters are proposed.The results indicate that the strain hardening parameter can be neglected and the behavior of the thin steel jacket can be described by a modeling without strain hardening sensitivity.

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.

Improvement of breakdown characteristics of an A1GaN/GaN HEMT with a U-type gate foot for millimeter-wave power application

In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor （HEMT） with a U-type gate foot. The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle, which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics. At the same time, only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device. U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system, without introducing any extra process steps. The simulation results are confirmed by experimental measurements. These features indicate that U-gate A1GaN/GaN HEMTs might be promising candidates for use in millimeter-wave power applications.

Dynamic Response of the U-Typed Sandwich Panel Under Explosion Load Based on the SDOF Method

Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic response of the U-typed sandwich panel under explosion load through the numerical simulation and theoretical methods.Based on the orthotropic plate theory,the U-typed sandwich panel is simplified and transformed into a single degree of freedom(SDOF)spring system,the equivalent motion equation of the SDOF system and the expression of triangular explosion load function are established based on the SDOF theory,and the maximum response spectrum of the SDOF system is obtained.Then,the response of the equivalent SDOF system of the U-typed sandwich panel under explosion load is analyzed,and the theoretical results match well with the numerical simulation results,which verifies the accuracy of the theoretical method proposed in this paper.The theoretical method proposed in this paper could have good engineering applications for the structural anti-explosion design,and provide a reference for the evaluation of the anti-explosion performance of ship and offshore platform structures.

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.

U-Type Designs via New Generalized Partially Balanced Incomplete Block Designs with <i>m</i>= 4, 5 and 7 Associated Classes

The traditional combinatorial designs can be used as basic designs for constructing designs of computer experiments which have been used successfully till now in various domains such as engineering, pharmaceutical industry, etc. In this paper, a new series of generalized partially balanced incomplete blocks PBIB designs with m associated classes (m = 4, 5 and 7) based on new generalized association schemes with number of treatments v arranged in w arrays of n rows and l columns (w ≥ 2, n ≥ 2, l ≥ 2) is defined. Some construction methods of these new PBIB are given and their parameters are specified using the Combinatory Method (s). For n or l even and s divisor of n or l, the obtained PBIB designs are resolvable PBIB designs. So the Fang RBIBD method is applied to obtain a series of particular U-type designs U (wnl;) (r is the repetition number of each treatment in our resolvable PBIB design).

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。

深水大容量吸力筒导管架风机基础设计

为适应海上风电事业逐步向深远海、大容量机组发展的趋势,研发适用于更复杂海洋环境条件的风机基础势在必行。吸力筒导管架式基础因其施工方便、承载能力高、地层适用性广泛等优点,在海上风电基础设计中备受关注。以某大容量海上风机为研究对象,基于常用海工设计软件对结构进行一体化的整体受力特性研究;采用ANSYS软件对过渡段及筒体进行局部强度的计算分析。计算结果表明吸力筒导管架基础满足各项控制指标,具备良好的承载能力与稳定性。研究成果可为后续的深水远海固定式基础设计提供参考。

剪切模式对砂-钢界面特性的影响

针对海上风机导管架基础在安装过程中发生的桩土界面单向剪切行为和服役过程中发生的持续循环剪切行为,分别采用常应力和等刚度边界条件对石英砂/钙质砂开展单向和循环剪切试验,研究不同剪切模式下界面强度发挥的细观作用。结果发现:随着单向剪切距离的增加,土样破碎带厚度逐渐增大,钢界面粗糙度下降;循环剪切幅值越大,颗粒排布重塑越充分,产生的法向位移越大。在大位移单向剪切和循环剪切过程中,破碎带的存在会改变土体的初始结构,使其具有强烈方向性。由于钙质砂的硬度较低,同等粒径下其形状相比石英砂颗粒更不规则,因此其在同等剪切距离下会产生更大的破碎量,引起较大体缩,而破碎后的石英砂棱角较多,在钢界面扰动下更易发生旋转,引起大位移单向剪切后的循环剪切过程中土样剪胀增加。

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。

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。

广绣图案在时尚皮革服饰品设计中的创新应用

广绣是首批被国务院核准的非物质文化遗产。广绣图案具有深厚的艺术底蕴与突出的应用价值,在过去一千多年的历史中起到了美化人们生活的重要作用。总结广绣图案的艺术特征,提出对应的创新设计方法,创作多款新型图案,将其应用于皮衣等现代皮革服饰品中,展示出了广绣图案强大的装饰性与独特优势。研究广绣图案在时尚服饰设计中的创新应用,对促进中国传统文化在现代社会中的传承,推动我国纺织服装行业高质量发展具有实际作用与意义,同时也为业界提供一些行之有效的设计思路与方法。

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。

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。

海上风电三筒导管架基础的湿拖耦合动力响应研究

[目的]为提高海上风电多筒导管架基础的湿拖运输安全性,需探究其湿拖运输过程的稳性和动态响应问题。[方法]基于海工分析软件MOSES构建水动力模型,对湿拖运输过程分别进行频域和时域分析,并定量分析波浪载荷、拖航方式等参数对三筒导管架基础拖航特性的影响。[结果]计算结果表明,三筒导管架具有良好的湿拖稳性,在吃水深度8~10 m范围内的正浮态均可满足完整稳性校核;三筒导管架基础的拖缆力、纵摇角、垂荡加速度、筒气压的幅值与波高呈正比关系,与吃水深度呈线性变化关系但影响较小;拖缆力和筒气压的幅值与波浪周期无明显关系,但波浪周期将影响该基础的纵摇和垂荡响应幅值;拖缆力与航速的平方近似呈正比关系;顺浪条件下三筒导管架基础的纵摇运动比逆浪条件更为剧烈。[结论]研究成果对于提高多筒导管架基础的湿拖运输安全性具有重要的指导意义。