Ocean Engineering最新文献_第7页

Hydrodynamic performance and energy efficiency of an undulating fin based on the composite motion of oscillation and pitch 基于摆动和俯仰复合运动的起伏鳍的水动力性能和能效

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2024-11-09 DOI: 10.1016/j.oceaneng.2024.119707

Qian Yin , Minghai Xia , Zhangmao Hu , Jinqiao He , Zirong Luo

Fish-like robots have become underwater vehicles with broad application prospects, owing to their flexibility and adaptability. Inspired by the swimming motion of fish, an undulating fin with composite motion is proposed in this study. The composite motion is a combination of oscillation and pitch perpendicular to and parallel to the horizontal direction, respectively. First, the kinematic and dynamic modes of the motion mechanism in the free propulsive mode are established with variable locomotive parameters, such as the oscillating frequency and deflection angle. The hydrodynamic performance of the undulating fin is then investigated through analyses of the force mechanism, propulsive velocity, non-dimensional number, and vortex flow using the dynamic mesh method. The energy efficiency of the composite motion of undulating fin is compared with that of a simple oscillating motion. Finally, experimental measurements of an undulating-fin robot prototype are conducted. The results show that the underwater robot accelerates to a maximum velocity of 0.54 m/s with a frequency of 2.5 Hz. Owing to the composite motion, alternating high and low-velocity regions occur in the surrounding fluid of the undulating fin. The highest energy efficiency is 0.88 with a frequency of 2.0 Hz, and the maximum improvement is 10.1% compared with the simple oscillating motion. A streamwise central jet is formed with vortices shedding into the wake flow, which generates a thrust force with two peaks and troughs in one cycle. The negative and positive vorticities correspond to the alternation of the pressure distribution. The experimental measurements demonstrate the propulsive velocity and force are consistent with the numerical simulation. The composite motion with a higher Strouhal number reflects the considerable instability of the flow.

鱼类机器人因其灵活性和适应性，已成为具有广阔应用前景的水下运载工具。受鱼类游泳运动的启发，本研究提出了一种具有复合运动的起伏鳍。复合运动分别是垂直于水平方向的摆动和平行于水平方向的俯仰。首先，在摆动频率和偏转角等运动参数可变的情况下，建立了自由推进模式下运动机构的运动学和动力学模式。然后，利用动态网格法，通过对力机制、推进速度、非维数和涡流的分析，研究了起伏鳍的流体力学性能。起伏鳍复合运动的能量效率与简单摆动运动的能量效率进行了比较。最后，对起伏鳍机器人原型进行了实验测量。结果表明，水下机器人的最大加速度为 0.54 米/秒，频率为 2.5 赫兹。由于是复合运动，起伏鳍周围流体中出现了高速和低速交替区域。与简单的摆动运动相比，频率为 2.0 Hz 时的最高能量效率为 0.88，最大提高幅度为 10.1%。流向中心的射流与尾流中脱落的涡流一起形成了推力，在一个周期内产生了两个波峰和波谷。正负涡流与压力分布的交替相对应。实验测量结果表明，推进速度和推进力与数值模拟结果一致。斯特劳哈尔数越高，复合运动越大，这反映出气流相当不稳定。

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引用次数: 0

Steady-state response of an infinite, free floating ice sheet to a moving load at constant velocity 无限自由浮动冰层对匀速运动载荷的稳态响应

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2024-11-09 DOI: 10.1016/j.oceaneng.2024.119627

J. Qiu , Z.Q. Wang

This study investigates the steady-state response of a thin elastic plate floating on the surface of an infinitely deep compressible fluid to a moving line load. The load travels at a constant speed along the axial direction in the one-dimensional model. A steady-state solution was theoretically established for the moving load, and the expressions for the vertical displacement and pressure, and velocity in the fluid were explicitly determined. Integral transforms and asymptotic methods were used to derive a semi-analytical solution for the steady-state response, and the influence of the plate thickness and velocity of the moving load on the fluid domain pressure and the structure interaction response of the plate is thoroughly discussed. Numerical analysis results indicate that when the moving force traverses a large coupled elastic plate at a constant velocity, a portion of the response gradually evolves into a steady-state condition. This study uniquely addresses the steady-state response of an ice sheet in contact with a compressible fluid under subsonic conditions, a less explored area in existing literature. The findings have significant implications for the design and safety of infrastructure in Arctic regions.

本研究探讨了漂浮在无限深的可压缩流体表面上的弹性薄板对移动线载荷的稳态响应。在一维模型中，载荷沿轴向匀速运动。从理论上建立了移动载荷的稳态解，并明确确定了流体中的垂直位移、压力和速度的表达式。利用积分变换和渐近法得出了稳态响应的半解析解，并深入讨论了板厚度和移动载荷速度对流体域压力和板结构相互作用响应的影响。数值分析结果表明，当移动力以恒定速度穿越大型耦合弹性板时，部分响应会逐渐演变为稳态条件。这项研究独特地探讨了亚音速条件下冰层与可压缩流体接触时的稳态响应，这是现有文献中较少探讨的领域。研究结果对北极地区基础设施的设计和安全具有重要意义。

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引用次数: 0

Experimental and numerical simulation study of drag reduction on AUV grooved surfaces 减少 AUV 沟槽表面阻力的实验和数值模拟研究

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2024-11-08 DOI: 10.1016/j.oceaneng.2024.119610

Siqi Zhang , Xiaoyi Wu , Shan Ma , Ziqian Wang , Zhuo Sun , Ming Hu

In the study of hydrodynamic performance of Autonomous Underwater Vehicles (AUVs), drag reduction is a crucial aspect that can significantly lower energy consumption and enhance operational range. Groove drag reduction, a form of passive drag reduction technology, is widely employed across various fields due to its simple structure and broad applicability. Implementing grooved surfaces on AUVs is an effective solution for reducing drag. This paper investigates the resistance of AUVs with grooved surfaces through experimental methods and comparative testing. A full-scale numerical simulation utilizing two-phase flow is also conducted, revealing that the resistance reduction results align closely with the trends observed in model tests. The maximum drag reduction achieved in the experiments is 8.13%. While discrepancies exist between numerical and experimental results, the overall physical principles remain consistent.

在自主潜水器（AUV）的水动力性能研究中，减少阻力是一个至关重要的方面，它可以显著降低能耗，提高续航能力。沟槽减阻作为一种被动减阻技术，因其结构简单、适用性广而被广泛应用于各个领域。在自动潜航器上采用凹槽表面是减少阻力的有效解决方案。本文通过实验方法和对比测试研究了带有沟槽表面的 AUV 的阻力。此外，还利用两相流进行了全尺寸数值模拟，结果表明阻力减少的结果与模型试验中观察到的趋势非常吻合。实验中实现的最大阻力降低率为 8.13%。虽然数值结果和实验结果之间存在差异，但总体物理原理保持一致。

引用次数: 0

Wingsail performance in unsteady atmospheric surface layer winds 不稳定大气表层风中的翼帆性能

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2024-11-08 DOI: 10.1016/j.oceaneng.2024.119653

Clément Bouhourd, Laurent Perret, Carlo Cossu

The performance of wind propulsion systems is evaluated in unsteady inhomogeneous winds with tools that are routinely used to predict the performance of wind turbines and which give access to the unsteady aerodynamic forces acting on the wingsail. A rigid wingsail exposed to a realistic atmospheric surface layer wind is used as a testbed. For this case, we show that standard deviations of the aerodynamic driving force are larger than 15%–20% of the mean values when the true wind velocity is larger than the ship speed. We also show that the mean aerodynamic driving forces computed by averaging the unsteady driving forces are only slightly smaller than the ones computed on the mean wind despite the strongly nonlinear dependence of the unsteady forces on the wind velocity and direction.

风力推进系统在非稳定非均质风中的性能评估采用的工具通常用于预测风力涡轮机的性能，并可获得作用在翼尾上的非稳定空气动力。我们使用暴露在真实大气表层风中的刚性翼帆作为试验台。在这种情况下，我们发现当真实风速大于船速时，空气动力驱动力的标准偏差大于平均值的 15%-20%。我们还表明，尽管非稳定驱动力与风速和风向存在强烈的非线性关系，但通过平均非稳定驱动力计算出的平均气动驱动力仅略低于根据平均风速计算出的气动驱动力。

引用次数: 0

Analyzing AIS and wave hindcast data for global wave scatter diagrams with seasonality 分析 AIS 和波浪后报数据，绘制具有季节性的全球波浪散点图

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2024-11-08 DOI: 10.1016/j.oceaneng.2024.119647

Wataru Fujimoto, Kinya Ishibashi, Tingyao Zhu

Global scatter diagrams are used to estimate possible ship motions in a specified route and are required for comprehensive cargo-loading considerations of merchant ships. This study aims to update global wave scatter diagrams using the latest wave hindcast and Automatic Identification System (AIS) data. The AIS data for over 7500 merchant ships were collected between 2015 and 2022. The wave hindcast data ECMWF Reanalysis v.5 (ERA5), preferred for its recent coverage, were adjusted based on CCI satellite data. The duration of the AIS data is much shorter than the design lifetime of merchant ships, which is generally 25 years. This study found almost linear relationships between the maximum significant wave heights in storms and the generalized extreme value (GEV) parameters representing the distribution of encountered significant wave heights, with adjustments made for seasonality and tropical cyclones. By simulating the parameters based on these relationships and the wave hindcast data over 25 years, the encountered significant wave height distributions over 25 years were obtained. The results indicated a reduction in extremely significant wave heights compared with the BMT-GWS, in agreement with previous studies. This study also found that the difference in the wave period distribution between natural and encountered sea states was small in most sea areas for all significant wave height levels. Taking advantage of the abundant data volume of ERA5, this study adopted an empirical distribution of the wave period conditioned by the significant wave height. The novelty of this study is that we obtained wave scatter diagrams globally by month to consider the seasonal effect in detail and evaluated the confidence interval of the encountered wave height in its probability tail. In addition, this study quantifies the uncertainty of the wave height distribution by Monte Carlo simulation, which is not within the scope of previous studies on wave scatter diagrams based on the significant wave heights encountered by merchant ships around the world.

全球散点图用于估算指定航线上可能出现的船舶运动，也是商船全面考虑货物装载所必需的。本研究旨在利用最新的波浪后报和自动识别系统（AIS）数据更新全球波浪散布图。在 2015 年至 2022 年期间，收集了超过 7500 艘商船的自动识别系统数据。波浪后报数据 ECMWF Reanalysis v.5 (ERA5) 因其最近的覆盖范围而受到青睐，并根据 CCI 卫星数据进行了调整。AIS 数据的持续时间远短于商船的设计寿命（一般为 25 年）。这项研究发现，风暴中的最大显著波高与代表所遇到的显著波高分布的广义极值 (GEV) 参数之间几乎呈线性关系，并根据季节性和热带气旋进行了调整。通过模拟基于这些关系的参数和 25 年的波浪后报数据，得到了 25 年的遭遇巨浪高度分布。结果表明，与 BMT-GWS 相比，极显著波高有所降低，这与之前的研究结果一致。这项研究还发现，在大多数海域，所有显著波高等级下，自然海况和遭遇海况的波浪周期分布差异很小。利用 ERA5 丰富的数据量，本研究采用了以显著波高为条件的波浪周期经验分布。本研究的新颖之处在于，我们获得了全球各月的波浪散点图，详细考虑了季节效应，并评估了所遇波浪高度在其概率尾部的置信区间。此外，本研究还通过蒙特卡洛模拟对波高分布的不确定性进行了量化，这是以往根据商船在世界各地遇到的显著波高绘制波浪散布图的研究范围所不具备的。

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引用次数: 0

Numerical simulation of the relationship between steam flow excitation characteristics and coverage on the governing stage of marine steam turbine 蒸汽流激波特性与船用蒸汽轮机调节级覆盖率之间关系的数值模拟

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2024-11-08 DOI: 10.1016/j.oceaneng.2024.119526

Tao Sun , Yingzhuo Liu , Zhenlai Ma , Peng Shu , Zhenyu Ye

“Coverage” refers to the disparity between the inlet height of the rotor blade and the outlet height of the nozzle blade in the governing stage of steam turbines. The adoption of partial admission operating mode exacerbates the instability of the internal flow field. Therefore, investigating the influence of coverage on the governing stage's internal flow field is of paramount importance. In this regard, numerical simulations are conducted to analyze the internal flow field of the governing stage under partial admission operation, aiming to explore the impact of coverage variation. The results show that coverage significantly affects the excitation characteristics. The steam flow excitation force of the governing stage rotor blades under partial admission will fluctuate periodically in the flow zone of the steam flow. There will be a sudden increase in pressure at the rotating outlet end, particularly at the rotation frequency, two times the rotation frequency, and the blade pass frequency, exhibiting substantial amplitude. Adjusting the coverage to reduce the amplitude of the excitation force at the rotation frequency will result in an increase in the amplitude at the blade pass frequency. This study provides a reference for the design of the coverage of marine steam turbines.

"覆盖率 "是指汽轮机调节级转子叶片进口高度与喷嘴叶片出口高度之间的差距。采用部分接纳运行模式会加剧内部流场的不稳定性。因此，研究覆盖范围对调节级内部流场的影响至关重要。为此，我们进行了数值模拟，分析了部分接纳运行下的调节级内部流场，旨在探讨覆盖率变化的影响。结果表明，覆盖率对激振特性有很大影响。部分吸入时，调节级转子叶片的蒸汽流激振力会在蒸汽流的流动区域内周期性波动。旋转出口端的压力会突然增加，尤其是在旋转频率、两倍旋转频率和叶片通过频率时，会表现出很大的振幅。调整覆盖范围以减小旋转频率时的激振力振幅，会导致叶片通过频率时的振幅增大。这项研究为船用蒸汽轮机的覆盖面设计提供了参考。

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引用次数: 0

Parametric analysis of pseudo-shakedown behaviour of plates under repeated impacts 反复冲击下板材伪震动行为的参数分析

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2024-11-08 DOI: 10.1016/j.oceaneng.2024.119675

Xu He, C. Guedes Soares

This article conducts a parametric analysis to investigate how dynamic material properties, plate dimensions, and boundary conditions affect the pseudo-shakedown behaviour of plates under repeated impacts. Validated numerical simulation methods are employed for this analysis. Different constitutive equations accounting for strain rate effects are used to vary dynamic material properties. Plate dimensions are varied in terms of aspect ratios and plate thicknesses. Various boundary conditions, including fully fixed boundary and conditions allowing in-plane sliding, are considered. The analysis reveals that strain rate effects, plate dimensions and boundary conditions significantly affect the pseudo-shakedown response to repeated impacts. A discussion is made on the challenges and considerations in accurately modelling strain rate effects and boundary conditions in numerical simulations. The findings of this parametric analysis are useful for designing ship plates to withstand repeated impacts, when incorporating pseudo-shakedown concept in design strategies.

本文通过参数分析来研究动态材料特性、板材尺寸和边界条件如何影响板材在反复撞击下的伪震动行为。该分析采用了经过验证的数值模拟方法。使用不同的应变率效应构成方程来改变动态材料属性。板的尺寸因长宽比和板厚而异。考虑了各种边界条件，包括完全固定的边界和允许平面内滑动的条件。分析表明，应变率效应、板尺寸和边界条件对反复冲击的伪振动响应有显著影响。讨论了在数值模拟中准确模拟应变率效应和边界条件的挑战和注意事项。这一参数分析的结果有助于在将伪振动概念纳入设计策略时，设计船板以承受反复撞击。

引用次数: 0

Hydrodynamic characteristics and internal flow field of a perforated fishing vessel under wave conditions 波浪条件下穿孔渔船的水动力特性和内部流场

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2024-11-08 DOI: 10.1016/j.oceaneng.2024.119611

Xi Zhang , Junjun Lv , Dachuan He , Ke Wang , Ying Liu , Jie Zhi

This research focuses on an innovative design of a perforated fishing vessel, aiming to precisely and efficiently evaluate its hydrodynamic performance and the characteristics of its internal flow fields. Initially, the boundary element method is employed to tackle the challenge of hydrodynamic responses in structures with arbitrary openings, quantifying added mass, damping effects, and dynamic responses under various filling scenarios. This sets a foundation for assessing structural stability. Subsequently, using the CFD method, based on the Navier–Stokes equations, a deep exploration into the mechanisms of how fluid viscosity and nonlinear effects influence the flow fields inside and outside the culture compartments is conducted. This reveals the impact of detailed flow field features on the fish welfare of fishing vessel design. The CFD method implemented the forced motion of the aquaculture fishing vessel based on FLUENT UDF, with the specific parameters of the moving boundary conditions determined by the results of the BEM method. The frequency-domain results show that the heave motion response is significantly greater than the sway. Compared with the isolated heave flow field results, the coupling heave-roll motion causes obvious vortex phenomena in the fluid on both sides of the perforated fishing vessel.

本研究侧重于穿孔渔船的创新设计，旨在精确有效地评估其水动力性能及其内部流场的特征。首先，采用边界元方法解决任意开口结构的流体动力学响应难题，量化附加质量、阻尼效应和各种填充情况下的动态响应。这为评估结构稳定性奠定了基础。随后，利用基于纳维-斯托克斯方程的 CFD 方法，深入探讨了流体粘度和非线性效应对培养舱内外流场的影响机制。这揭示了详细的流场特征对渔船设计中鱼类福利的影响。基于 FLUENT UDF 的 CFD 方法实现了水产养殖渔船的强制运动，运动边界条件的具体参数由 BEM 方法的结果确定。频域结果表明，波浪运动响应明显大于摇摆运动响应。与孤立的翻滚流场结果相比，翻滚-滚动耦合运动在穿孔渔船两侧流体中引起了明显的涡流现象。

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引用次数: 0

Scale effects on wave loads and slamming loads in ship hydroelasticity simulation by CFD-FEM method 利用 CFD-FEM 方法模拟船舶水弹性时波浪载荷和撞击载荷的尺度效应

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2024-11-08 DOI: 10.1016/j.oceaneng.2024.119718

Zhenwei Chen , Jialong Jiao , Caixia Jiang , Hailong Si , Shuai Chen

A partitioned CFD-FEM two-way coupled method is employed to simulate the wave loads and hydroelasticity of a 310-m-long ship at different scales and the scale effects are investigated. Four different scales, including three model scale 1:100, 1:50, 1:25 and one full-scale 1:1, of the ship under equivalent wave conditions are calculated for comparison. The results of the resistance in waves, global motions, wave loads, slamming and green water pressures for ships at different scales are comparatively analyzed from the aspects of time series, frequency spectra and statistics values to investigate the scale effects. The research interest mainly lies in the scale effect on slamming and green water pressures on the flexible ships. The scale effects on ship seakeeping and slamming pressures by pure CFD simulation are also comparatively studied. It can be concluded that the scale effect has little influence on ship vertical motions and loads, while it has more influence on slamming pressure loads and green water on deck, but the deviation caused by other uncertainty factors can be comparable with that of scale effects.

采用分区 CFD-FEM 双向耦合方法模拟了长 310 米的船舶在不同尺度下的波浪载荷和水弹性，并研究了尺度效应。为了进行比较，计算了等效波浪条件下四种不同比例的船舶，包括三种模型比例 1:100、1:50、1:25 和一种全比例 1:1。从时间序列、频谱和统计值等方面比较分析了不同尺度下的船舶在波浪中的阻力、全局运动、波浪载荷、撞击和绿水压力等结果，以研究尺度效应。研究兴趣主要集中在尺度效应对柔性船舶碰撞和绿水压力的影响上。同时，通过纯 CFD 模拟，对比研究了尺度效应对船舶适航性和倾覆压力的影响。可以得出结论：尺度效应对船舶垂直运动和载荷影响较小，而对甲板上的倾覆压力载荷和绿水影响较大，但其他不确定性因素造成的偏差可与尺度效应的偏差相媲美。

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引用次数: 0

Bio-inspired profile improving the flow near the stern of an underwater vehicle 改善水下航行器尾部附近水流的生物启发轮廓

IF 4.6 2区工程技术 Q1 ENGINEERING, CIVIL

Ocean Engineering

Pub Date : 2024-11-08 DOI: 10.1016/j.oceaneng.2024.119693

Zhuoyu Xie, Yi Liu, Shizhao Wang, Guowei He

The utilization of underwater vehicles is becoming increasingly prevalent in a number of fields, including marine resource exploration, exploitation, and oceanographic research. The wake induced by the motion of these vehicles has the potential to significantly affect the efficiency of the vehicles. This paper draws inspiration from the sperm whale profile and investigates a bio-inspired underwater vehicle, BioUV. The bio-inspired underwater vehicle incorporates an integrated sail as an alternative to the classical sail. The flow uniformity in the stern region is assessed using the integral non-uniformity coefficient. The differences in turbulent kinetic energy in the stern region are discussed, and the effects of hull profiles on flow uniformity and turbulent kinetic energy are further investigated. Furthermore, the resistance is evaluated based on wall pressure and wall shear stress. The results reveal that, without increasing the resistance of the bio-inspired underwater vehicle, BioUV without a parallel middle body can effectively mitigate the strong adverse pressure gradient at the stern (

x / L \approx 0.85

) caused by the classical hull profile, reduce flow non-uniformity (

x / L \approx 0.88 \sim 0.97

) and turbulent kinetic energy (

x / L \approx 0.90 \sim 0.97

) in the stern region.

在海洋资源勘探、开发和海洋学研究等多个领域，水下航行器的使用正变得越来越普遍。这些潜水器运动时产生的尾流可能会严重影响潜水器的效率。本文从抹香鲸的外形中汲取灵感，研究了一种生物启发水下航行器 BioUV。该生物启发式水下航行器采用了集成风帆来替代传统风帆。船尾区域的流动均匀性通过积分不均匀系数进行评估。讨论了船尾区域湍流动能的差异，并进一步研究了船体轮廓对流动均匀性和湍流动能的影响。此外，还根据壁面压力和壁面剪应力对阻力进行了评估。结果表明，在不增加生物启发式水下航行器阻力的情况下，不带平行中间体的生物启发式水下航行器可以有效缓解经典船体剖面在船尾造成的强烈不利压力梯度（x/L≈0.85），降低船尾区域的流动不均匀性（x/L≈0.88∼0.97）和湍流动能（x/L≈0.90∼0.97）。

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引用次数: 0