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In-line flow-induced vibration of rotating elliptical cylinders 旋转椭圆形气缸的在线流动诱导振动
IF 3.4 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2024-09-21 DOI: 10.1016/j.jfluidstructs.2024.104186
Yan Wu , Yuqi Huang , Jisheng Zhao
<div><p>This study numerically investigates the in-line flow-induced vibration (FIV) of elastically mounted elliptical cylinders undergoing forced rotations in a free-stream flow. The two-dimensional numerical simulations were conducted at a Reynolds number of 100. The cross-sectional aspect ratio (or elliptical ratio) of the cylinders varied from 1 to 0.25. The aspect/elliptical ratio is defined by <span><math><mrow><mi>ϵ</mi><mo>=</mo><mn>2</mn><mi>b</mi><mo>/</mo><mn>2</mn><mi>a</mi></mrow></math></span>, where <span><math><mrow><mn>2</mn><mi>a</mi></mrow></math></span> and <span><math><mrow><mn>2</mn><mi>b</mi></mrow></math></span> are the streamwise and cross-flow dimensions, respectively, of the cross-section of a cylinder placed at zero incidence angle. The Reynolds number is defined by <span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mi>U</mi><mi>D</mi><mo>/</mo><mi>ν</mi></mrow></math></span>, where <span><math><mi>U</mi></math></span> is the free-stream velocity, <span><math><mi>ν</mi></math></span> is the kinematic viscosity of the fluid, and <span><math><mi>D</mi></math></span> is the major axis length (i.e. <span><math><mrow><mi>D</mi><mo>=</mo><mn>2</mn><mi>a</mi></mrow></math></span>). The dimensionless rotation rate, defined by <span><math><mrow><mi>α</mi><mo>=</mo><mrow><mo>|</mo><mi>Ω</mi><mo>|</mo></mrow><mi>D</mi><mo>/</mo><mrow><mo>(</mo><mn>2</mn><mi>U</mi><mo>)</mo></mrow></mrow></math></span>, is varied at values of 0.2, 0.5, 1 and 2, where <span><math><mi>Ω</mi></math></span> represents the angular velocity of the body rotation. The FIV response is examined as a function of reduced velocity, defined by <span><math><mrow><msup><mrow><mi>U</mi></mrow><mrow><mo>∗</mo></mrow></msup><mo>=</mo><mi>U</mi><mo>/</mo><mrow><mo>(</mo><msub><mrow><mi>f</mi></mrow><mrow><mi>n</mi></mrow></msub><mi>D</mi><mo>)</mo></mrow></mrow></math></span>, with <span><math><msub><mrow><mi>f</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> being the natural frequency of the system. Interestingly, two synchronisation modes were identified: a “rotation-dominated” (RD) mode and a “wake-dominated” (WD) mode. For <span><math><mrow><mi>α</mi><mo>∈</mo><mrow><mo>{</mo><mn>0</mn><mo>.</mo><mn>2</mn><mo>,</mo><mn>0</mn><mo>.</mo><mn>5</mn><mo>,</mo><mn>1</mn><mo>}</mo></mrow></mrow></math></span>, the RD mode was found to be associated with significantly high-amplitude vibration, while the WD mode was associated with low-amplitude vibration. However, as <span><math><mi>α</mi></math></span> increased to 2, the WD region exhibited a higher amplitude peak compared to the RD region. The maximum vibration amplitude in the present study was observed to be approximately <span><math><mrow><mn>0</mn><mo>.</mo><mn>5</mn><mi>D</mi></mrow></math></span>, occurring for <span><math><mrow><mi>α</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>2</mn></mrow></math></span>. A further analysis of the wake structure revealed that vortex feeding or merging behaviour occurred at <spa
本研究以数值方法研究了在自由流中受力旋转的弹性安装椭圆形圆柱体的线内流动诱导振动(FIV)。二维数值模拟在雷诺数为 100 时进行。圆柱体的横截面长宽比(或椭圆比)从 1 到 0.25 不等。长宽比/椭圆比的定义是 ϵ=2b/2a,其中 2a 和 2b 分别是零入射角放置的圆柱体横截面的流向尺寸和横流尺寸。雷诺数的定义是 Re=UD/ν,其中 U 是自由流速度,ν 是流体的运动粘度,D 是主轴长度(即 D=2a)。无量纲旋转速率的定义为 α=|Ω|D/(2U),其变化值为 0.2、0.5、1 和 2,其中 Ω 代表主体旋转的角速度。根据 U∗=U/(fnD) 的定义(ffn 是系统的固有频率),将 FIV 响应作为减速度的函数进行检验。有趣的是,研究发现了两种同步模式:"旋转主导"(RD)模式和 "唤醒主导"(WD)模式。对于 α∈{0.2,0.5,1},发现 RD 模式与明显的高振幅振动相关,而 WD 模式与低振幅振动相关。然而,当 α 增大到 2 时,WD 区域的振幅峰值高于 RD 区域。本研究中观察到的最大振幅约为 0.5D,发生在 α=0.2 时。对尾流结构的进一步分析表明,当ϵ=0.25 时,α=0.5、1 和 2 时出现涡流馈入或合并行为;当 α=0.5 时,ϵ⩽0.75 时出现涡流馈入或合并行为。提高旋转率或长宽比可以减弱旋转对振动的影响,从而降低 RD 区域的峰值振幅。值得注意的是,在 α=0.2 时,观察到了超过旋转频率的谐波频率成分。通过对固定体的进一步研究发现,当 α<0.3 时,旋转椭圆形圆柱体的唤醒模式会发生转变,表现出明显的不稳定性,其特征是高阶谐波成分的叠加。
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The aspect/elliptical ratio is defined by &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;ϵ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mi&gt;b&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, where &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mi&gt;b&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; are the streamwise and cross-flow dimensions, respectively, of the cross-section of a cylinder placed at zero incidence angle. The Reynolds number is defined by &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;ν&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, where &lt;span&gt;&lt;math&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; is the free-stream velocity, &lt;span&gt;&lt;math&gt;&lt;mi&gt;ν&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; is the kinematic viscosity of the fluid, and &lt;span&gt;&lt;math&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; is the major axis length (i.e. &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). The dimensionless rotation rate, defined by &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mrow&gt;&lt;mo&gt;|&lt;/mo&gt;&lt;mi&gt;Ω&lt;/mi&gt;&lt;mo&gt;|&lt;/mo&gt;&lt;/mrow&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, is varied at values of 0.2, 0.5, 1 and 2, where &lt;span&gt;&lt;math&gt;&lt;mi&gt;Ω&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; represents the angular velocity of the body rotation. The FIV response is examined as a function of reduced velocity, defined by &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;∗&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, with &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; being the natural frequency of the system. Interestingly, two synchronisation modes were identified: a “rotation-dominated” (RD) mode and a “wake-dominated” (WD) mode. For &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;∈&lt;/mo&gt;&lt;mrow&gt;&lt;mo&gt;{&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;}&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, the RD mode was found to be associated with significantly high-amplitude vibration, while the WD mode was associated with low-amplitude vibration. However, as &lt;span&gt;&lt;math&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; increased to 2, the WD region exhibited a higher amplitude peak compared to the RD region. The maximum vibration amplitude in the present study was observed to be approximately &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, occurring for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. A further analysis of the wake structure revealed that vortex feeding or merging behaviour occurred at &lt;spa","PeriodicalId":54834,"journal":{"name":"Journal of Fluids and Structures","volume":"130 ","pages":"Article 104186"},"PeriodicalIF":3.4,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142272016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Numerical study on propeller hydrodynamic excitation influenced by torsional vibration of shaft system 受轴系扭转振动影响的螺旋桨流体动力激励数值研究
IF 3.4 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2024-09-21 DOI: 10.1016/j.jfluidstructs.2024.104190
Chang-Lin Meng, Zhi-Jun Shuai, Lie-Yi Dong, Dong-Hua Wang, Wan-You Li

Torsional vibration of the propulsion shaft system has a significant influence on the safety and stability of marine navigation. Additionally, the resulting instantaneous fluctuation of rotational speed affects the hydrodynamic loading of propeller. To investigate this influence, a numerical model of propeller hydrodynamics influenced by hull wake and torsional vibration is established using delayed detached eddy simulation. First, the modeling method is described, and the model is verified and validated. Second, simulations are carried out for different amplitudes and frequencies of torsional vibration, and the hydrodynamic excitation, pressure pulsations and flow field features are analyzed detailly. The results show that torsional vibration significantly affects the hydrodynamic excitation of propeller, due to the fluctuations in blade section velocity, angle of attack and loading induced by instantaneous rotational speed, which can be equivalent to non-negligible added mass and damping. Through statistical analysis of the temporal-spatial pressure distribution, the complex modulation of torsional vibrations with different frequencies on the flow field from macroscopic hydrodynamic excitation to microscopic flow features is revealed. The effect of fluctuating small-amplitude loading on the dynamics and stability of propeller wake is also studied. This study provides theoretical support for designing and optimizing marine propellers and propulsion shaft systems.

推进轴系统的扭转振动对海上航行的安全性和稳定性有重大影响。此外,由此产生的转速瞬时波动也会影响螺旋桨的水动力负荷。为了研究这种影响,采用延迟分离涡模拟建立了受船体尾流和扭转振动影响的螺旋桨流体力学数值模型。首先,介绍了建模方法,并对模型进行了验证和确认。其次,对不同振幅和频率的扭转振动进行了模拟,并详细分析了水动力激励、压力脉动和流场特征。结果表明,由于桨叶截面速度、攻角和瞬时转速引起的载荷波动,扭转振动对螺旋桨的流体动力激振有显著影响,相当于增加了不可忽略的质量和阻尼。通过对时空压力分布的统计分析,揭示了不同频率的扭转振动对流场从宏观流体动力激励到微观流动特征的复杂调制。此外,还研究了小振幅波动载荷对螺旋桨尾流动力学和稳定性的影响。这项研究为设计和优化船用螺旋桨和推进轴系统提供了理论支持。
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引用次数: 0
Boundary conditions in flutter simulations of subsonic, transonic and supersonic blade cascades 亚音速、跨音速和超音速叶片级联扑动模拟的边界条件
IF 3.4 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2024-09-20 DOI: 10.1016/j.jfluidstructs.2024.104189
Marek Pátý , Jan Halama

Simulations of blade flutter are highly sensitive to undesired wave reflections at inlet and outlet boundaries. A careful treatment of boundary conditions is required to prevent the generation of perturbations. This study is motivated by the need to perform flutter analysis of low-pressure steam turbine blades, for which supersonic inflow conditions may occur in the near-tip region. The exact steady non-reflecting boundary condition (NRBC), the spectral NRBC and a simple isentropic boundary condition are implemented in a time-marching flow solver and applied to turbomachinery flutter simulations covering a wide range of operating conditions. For the first time, the spectral NRBC is applied to a blade flutter simulation with a supersonic inlet and its performance is analysed and compared with other boundary condition formulations. It is shown that an effective non-reflective treatment in the design of the boundary condition is essential for an accurate aeroelastic prediction at all operating conditions, including the subsonic flow regime. The limitation of the exact steady NRBC to spatial modes causes it to perform poorly in some unsteady flow simulations, whereas the spectral NRBC achieves a satisfactory suppression of undesired wave reflections in all investigated cases.

叶片扇动模拟对入口和出口边界的非预期波反射非常敏感。需要对边界条件进行仔细处理,以防止产生扰动。本研究的动机是需要对低压蒸汽轮机叶片进行扑动分析,因为在近叶尖区域可能会出现超音速流入条件。精确稳定非反射边界条件 (NRBC)、频谱 NRBC 和简单等熵边界条件在时间行进流求解器中得以实现,并应用于涵盖各种运行条件的透平机械扑动模拟。首次将光谱 NRBC 应用于带有超音速入口的叶片扑动模拟,并对其性能进行了分析,同时与其他边界条件公式进行了比较。结果表明,在设计边界条件时,有效的非反射处理对于在所有运行条件下(包括亚音速流动状态)进行精确的气动弹性预测至关重要。精确稳定非反射边界条件对空间模式的限制导致其在某些非稳定流模拟中表现不佳,而频谱非反射边界条件在所有研究案例中都能令人满意地抑制不期望的波反射。
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引用次数: 0
Rapidly deployable hulls and on-demand tunable hydrodynamics with shape morphing curved crease origami 利用形状变形弯曲折痕折纸实现可快速部署的船体和按需调节的流体力学
IF 3.4 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2024-09-11 DOI: 10.1016/j.jfluidstructs.2024.104176
Hardik Y. Patil , Kevin J. Maki , Evgueni T. Filipov

Traditional hull fabrication relies on labor- and time-intensive methods to generate smooth, curved surfaces. These conventional methods often lead to hull surface topologies that are static in design with hydrodynamics aimed at handling a broad range of sea conditions but not optimized for any specific scenario. In this paper, we introduce a method of rapidly fabricating planing hulls using the principles of curved-crease origami. Starting from a flat-folded state, the curved-crease origami hulls can be deployed to match traditional planing hull shapes like the VPS (deep-V, Planing hull with Straight face) and the GPPH (General Purpose Planing Hull). By extension of the ability to conform to a desired shape, we show that the curved-crease origami hulls can emulate desired hydrodynamic characteristics in still as well as wavy water conditions. Furthermore, we demonstrate the shape-morphing ability of curved-crease origami hulls, enabling them to switch between low and high deadrise configurations. This ability allows for on-demand tuning of the hull hydrodynamic performance. We present proof-of-concept origami hulls to demonstrate the practical feasibility of our method. Hulls fabricated using the curved-crease origami principles can adapt to different sea states, and their flat foldability and deployability facilitate easy transport and deployment for rapid response naval operations such as rescue missions and the launch of crewless aquatic vehicles.

传统的船体制造依赖于耗费大量人力和时间的方法来生成光滑的曲面。这些传统方法通常会导致船体表面拓扑结构在设计上是静态的,其流体力学旨在处理广泛的海况,但没有针对任何特定情况进行优化。在本文中,我们介绍了一种利用曲线折纸原理快速制造刨削船体的方法。从平面折叠状态开始,弧形皱褶折纸船体可用于匹配传统的刨削船体形状,如 VPS(深 V 直面刨削船体)和 GPPH(通用刨削船体)。通过扩展符合所需形状的能力,我们展示了弧形皱褶折纸船体可以在静水和波浪水条件下模拟所需的水动力特性。此外,我们还展示了弧形褶皱折纸船体的形状变形能力,使其能够在低死角和高死角配置之间切换。这种能力允许按需调整船体的水动力性能。我们展示了概念验证折纸船体,以证明我们的方法切实可行。利用弧形褶皱折纸原理制造的船体可适应不同的海况,其平面可折叠性和可部署性便于运输和部署,从而可用于快速反应海军行动,如救援任务和无船体水上运载工具的发射。
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引用次数: 0
Global stability analysis of flow-induced-vibration problems using an immersed boundary method 使用沉浸边界法对流动诱发振动问题进行全局稳定性分析
IF 3.4 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2024-09-11 DOI: 10.1016/j.jfluidstructs.2024.104187
Zhiyu Zhang, Jianfeng Lu, Xing Zhang

In this work, a numerical framework for global stability analysis of rigid-body-motion fluid–structure-interaction problems is presented. The Jacobian matrices which arise in the linearization procedure are derived numerically via the first-order finite difference scheme. The linearized fluid–structure coupled equations are solved using an immersed boundary method. The linear stability solver is first tested on two canonical cases, i.e., the flow past a stationary cylinder and the flow past an isolated elastically mounted cylinder. An excellent agreement between the results obtained here and those from available published research is achieved. The solver is then used to study the linear stability of the flow past two elastically mounted cylinders in tandem arrangement. The variations in growth rate and frequency of two leading modes with reduced velocity are examined. The mechanisms of lock-in and galloping phenomena observed in nonlinear simulation are elucidated from the perspective of linear instabilities in the leading modes.

本研究提出了对刚体运动流固耦合问题进行全局稳定性分析的数值框架。线性化过程中出现的雅各布矩阵是通过一阶有限差分方案数值推导出来的。线性化的流固耦合方程采用沉浸边界法求解。线性稳定性求解器首先在两种典型情况下进行了测试,即流过静止圆柱体和流过孤立的弹性安装圆柱体。测试结果与已发表的研究结果非常吻合。然后,利用求解器研究了流经串联布置的两个弹性安装圆柱体的线性稳定性。研究了两个前导模的增长率和频率随速度降低而变化的情况。从前导模态线性不稳定性的角度阐明了非线性模拟中观察到的锁定和奔腾现象的机理。
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引用次数: 0
Hydroelastic wave interaction with a circular crack of an ice-cover in a channel 水弹性波与河道冰盖圆形裂缝的相互作用
IF 3.4 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2024-09-09 DOI: 10.1016/j.jfluidstructs.2024.104173
Y.F. Yang, G.X. Wu, K. Ren

Hydroelastic wave interaction with a circular crack of an ice-cover in a channel together with some related problems is considered, based on the linearized velocity potential theory and Kirchhoff plate theory. The domain decomposition method is adopted in the solution procedure. Two sub-domains are divided by the crack, one below the inner ice sheet and the other below the outer ice sheet. By using the Green function of an ice-covered channel, the velocity potential in the outer domain is established from the source distribution formula over an artificial vertical surface extended from the crack. The source distribution is expanded in both vertical and circumferential directions, which allows the velocity potential to be obtained in an explicit form with unknown coefficients. The velocity potential in the inner domain is expanded into a double series. An orthogonal inner product is used to impose continuity conditions on the artificial vertical surface and the edge conditions at the crack. The derived formulation is not just limited to the circular crack problem but can also be readily used in a variety of other problems, including wave diffraction by a surface-piercing vertical cylinder, polynya and circular disc floating on the free surface in a channel. Extensive results are provided for the forces on the inner ice sheet, the transmission and reflection coefficients. In particular, a detailed analysis is made on their behaviours near the natural frequencies of the channel, and the natural frequencies corresponding to the motion of the inner ice sheet.

基于线性化速度势理论和基尔霍夫板理论,研究了水弹性波与水道中冰盖圆形裂缝的相互作用以及一些相关问题。求解过程采用了域分解法。通过裂缝划分出两个子域,一个位于内冰层下方,另一个位于外冰层下方。利用冰覆盖通道的格林函数,从裂缝延伸出的人工垂直面上的源分布公式确定外域的速度势能。源分布在垂直和圆周方向上都有扩展,因此可以用未知系数的显式形式获得速度势能。内域中的速度势展开为双序列。使用正交内积对人工垂直表面施加连续性条件,并在裂缝处施加边缘条件。推导出的公式不仅限于圆形裂缝问题,还可用于其他各种问题,包括表面穿透垂直圆柱体、多旋涡和漂浮在通道自由表面上的圆形圆盘的波衍射。文中提供了关于内部冰层受力、透射系数和反射系数的大量结果。特别是,详细分析了它们在通道自然频率附近的行为,以及与内冰片运动相对应的自然频率。
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引用次数: 0
Three-dimensional modeling and bandgap performance of a rotating phononic crystal pipe conveying fluid 旋转声子晶体管输送流体的三维建模和带隙性能
IF 3.4 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2024-09-04 DOI: 10.1016/j.jfluidstructs.2024.104172
Feng Liang, Yu Qian

Vibration and noise reduction of motional structures is a conventional challenge in a variety of industrial realms due to synchronous spatial motions present. In this case, optimizing structure design could provide a promising way for solution. Motivated by the idea of wave manipulation via phononic crystals (PCs), this paper aims to control three-dimensional (3D) vibration transmission of a rotating pipe by introducing an axial periodic design. The pipe is arranged as a composite structure comprised of alternate materials along the axial direction, and a constant fluid flows inside the pipe. Based on the Rayleigh beam theory, a set of 3D doubly-gyroscopic equations governing in-plane, out-of-plane flexural and axial motions of the pipe is established, which accounts for rotation gyroscopic force and fluid gyroscopic force. The spectral element technology is applied in such multi-dimensional system for solution. Following a validation by the finite element (FE) simulation, the band structure, frequency response function (FRF) and elastic wave shapes are presented to elucidate the 3D bandgap (BG) mechanism of the rotating PC pipe. The results obtained demonstrate the superior effectiveness of the proposed model for the 3D vibration suppression. Extensive parametric discussions reveal that the rotating motion, flowing fluid and geometry of the pipe all have significant impacts on the BG performance of the present rotating PC pipe system.

由于存在同步空间运动,运动结构的减振降噪是各种工业领域面临的传统挑战。在这种情况下,优化结构设计不失为一种可行的解决方案。受通过声子晶体(PC)操纵波的思想启发,本文旨在通过引入轴向周期性设计来控制旋转管道的三维(3D)振动传播。管道沿轴向布置为由交替材料组成的复合结构,管道内有恒定的流体流动。基于雷利梁理论,建立了一套三维双陀螺方程,用于控制管道的平面内、平面外挠曲和轴向运动,其中考虑了旋转陀螺力和流体陀螺力。在这种多维系统中采用了谱元技术进行求解。经过有限元(FE)模拟验证后,提出了频带结构、频率响应函数(FRF)和弹性波形,以阐明旋转 PC 管道的三维带隙(BG)机制。所获得的结果证明了所提出的模型在三维振动抑制方面的卓越功效。广泛的参数讨论表明,旋转运动、流动流体和管道的几何形状都会对现有旋转 PC 管道系统的带隙性能产生重大影响。
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引用次数: 0
On the role of wake-capture and resonance in spanwise-flexible flapping wings in tandem 跨度式柔性拍翼中的尾流捕捉和共振作用
IF 3.4 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2024-09-03 DOI: 10.1016/j.jfluidstructs.2024.104175
C. Martínez-Muriel , M. García-Villalba , O. Flores

Numerical simulations of the flow around spanwise-flexible flapping wings in tandem are reported, focusing on a thrust-generating configuration. Wings of aspect ratio 2 and 4 in forward flight undergo heaving and pitching motion following optimal 2D kinematics. The Reynolds number of the simulations is Re=1000. The effect of flexibility is explored by varying the effective stiffness of the wings, while the effective inertia is kept constant. The aerodynamic performance of the tandem system results from a combination of unsteady aerodynamics mechanisms, fluid–structure resonance, vortex–wing interactions (denoted wake capture in this study) and aerodynamic tailoring. It is found that the aerodynamic performance and structural behavior of forewings are dominated by a fluid–structural resonance. The maximum mean thrust for the forewings is obtained when the driving frequency approaches the first natural frequency of the structure, ωn,f/ω1, similarly to what is observed in isolated wings undergoing the same kinematics. On the other hand, hindwings show optimal performance in a broad region near ωn,f/ω2, and their aerodynamic performance seems to be dominated by wake–capture and aerodynamic–tailoring effects. The aerodynamic performance of the hindwings is dependent on the flexibility of the forewing, which impacts the intensity of the vortices shed into the wake and the resulting effective angle of attack (i.e., wake capture). The timing between the effective angle of attack and the pitching motion of the hindwing controls the generation of thrust (or drag) of each spanwise section of the hindwing (i.e., aerodynamic tayloring). A proof of concept study on the aerodynamic performance of systems made of wings with different flexibility suggests that they could outperform tandem systems with equally flexible wings. Thus, the optimal mixed–flexibility tandem system is composed by a resonant forewing, which maximizes the thrust generation of the forewing and the intensity of the vortices shed into the wake, and a hindwing whose flexibility must be tuned to maximize wake capture effects.

报告对串联的展弦柔性拍翼周围的气流进行了数值模拟,重点是产生推力的配置。长宽比分别为 2 和 4 的机翼在向前飞行时按照最佳二维运动学原理进行了起伏和俯仰运动。模拟的雷诺数为 Re=1000。在保持有效惯性不变的情况下,通过改变机翼的有效刚度来探索柔性的影响。串联系统的气动性能来自于非稳态空气动力学机制、流体-结构共振、涡翼相互作用(本研究中称为 "尾流捕获")和气动裁剪的组合。研究发现,前翼的气动性能和结构行为受流体-结构共振的支配。当驱动频率接近结构的第一固有频率ωn,f/ω≈1时,前翼会获得最大平均推力,这与在具有相同运动学特性的孤立机翼中观察到的情况类似。另一方面,后翼在ωn,f/ω≈2附近的广阔区域显示出最佳性能,其气动性能似乎主要受尾流捕获和气动尾翼效应的影响。后翼的气动性能取决于前翼的灵活性,前翼的灵活性会影响流向尾流的涡流强度以及由此产生的有效攻角(即尾流捕获)。有效攻角与后翼俯仰运动之间的时间关系控制着后翼每个跨度部分的推力(或阻力)的产生(即气动回旋)。对由不同柔性机翼组成的系统的气动性能进行的概念验证研究表明,这些系统的性能可能优于由同等柔性机翼组成的串联系统。因此,最佳的混合柔性串联系统由一个共振前翼和一个后翼组成,前翼可最大限度地产生推力,并使尾流中的涡流强度最大化,后翼的柔性必须进行调整,以最大限度地提高尾流捕获效果。
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引用次数: 0
A Single Center Experience: A Retrospective Study Over 10-Years Period on Mandible Fractures. 单个中心的经验:下颌骨骨折 10 年回顾性研究
IF 0.8 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2024-09-01 Epub Date: 2023-05-18 DOI: 10.1177/19433875231176338
Gabriele Monarchi, Riccardo Girotto, Mariagrazia Paglianiti, Paolo Balercia

Study design: The purpose of this study was to do a retrospective analysis about patients with mandibular fracture who were treated at the department of Maxillofacial Surgery, Regional University Hospital of Ancona, Italy, between 2011 and 2021.

Objective: In this study we evaluated clinical and epidemiological findings of mandible fractures focusing on the association between surgical timing, type of surgical approach and mid- and long-term outcomes.

Methods: Patients were evaluated based on various parameters including age, sex, etiology, symptoms, comorbidity, clinical findings, mandible fracture type, other facial fractures, treatment, waiting time before the operation, complications and sequelae. In the period described, we recorded 1023 mandibular fractures. 93% of patients underwent surgery under general anesthesia, almost exclusively patients undergoing an open approach to internal fixation.

Results: Of the patients, 684 were male (66.86%) and 339 were female (33.13%). The average age of the patients was 42, 38 years (range, 7-94 years). The leading cause of these fractures was traffic accidents (27.3%) and mandibular parasymphysis fractures were the most frequent (34.1%). The most common clinical signs and symptoms were malocclusion, difficulty in chewing, limitation of the buccal opening, hypoesthesia extending through the territory of the inferior alveolar nerve, difficulty in protrusion movements and mandibular lateralization.

Conclusions: The continuous research in epidemiology, etiology, materials, and techniques will further refine the treatments of mandible fractures, which are nowadays more and more customized according to the type of trauma.

研究设计:本研究旨在对2011年至2021年间在意大利安科纳地区大学医院颌面外科接受治疗的下颌骨骨折患者进行回顾性分析:在这项研究中,我们评估了下颌骨骨折的临床和流行病学调查结果,重点研究了手术时机、手术方式类型和中长期疗效之间的关联:根据患者的年龄、性别、病因、症状、合并症、临床表现、下颌骨骨折类型、其他面部骨折、治疗、手术前等待时间、并发症和后遗症等各种参数对患者进行评估。在所述期间,我们记录了 1023 例下颌骨骨折。93%的患者在全身麻醉下接受了手术,几乎所有患者都接受了开放式内固定手术:患者中,男性 684 人(66.86%),女性 339 人(33.13%)。患者平均年龄为 42.38 岁(7-94 岁不等)。造成这些骨折的主要原因是交通事故(27.3%),下颌骨副干骨折最为常见(34.1%)。最常见的临床症状和体征是错牙合畸形、咀嚼困难、颊部开口受限、下牙槽神经区域感觉减退、前突运动困难和下颌侧移:结论:对流行病学、病因学、材料和技术的不断研究将进一步完善下颌骨骨折的治疗方法,如今,下颌骨骨折的治疗方法越来越多地根据创伤类型进行定制。
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引用次数: 0
Modelling and analysis of two-dimensional static and dynamic aeroelasticity of Fish Bone Active Camber morphing aerofoils 鱼骨主动凸面变形气垫的二维静态和动态气动弹性建模与分析
IF 3.4 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2024-08-31 DOI: 10.1016/j.jfluidstructs.2024.104171
Jun Wu , Benjamin K.S. Woods

As a continuous and smooth morphing concept for aerofoils, the Fish Bone Active Camber (FishBAC) concept has demonstrated significant aerodynamic efficiency improvements over traditional hinged flaps. In this paper, to investigate the static and dynamic aeroelasticity of FishBAC aerofoils, an unsteady two dimensional coupled fluid-structure interaction model is developed, which includes the structural response of the FishBAC spine, skin, stringers, tendons and actuator, coupled to an unsteady aerodynamics model. The structural dynamic model is Timoshenko beam-theory-based, while the aerodynamic model is based on Peters’ unsteady model. The static and dynamic aeroelasticity is studied after the model is validated. Results show that the increase in pulley rotational angle reduces the zero-lift angle of attack, while keeping the slope between the lift coefficient and angle of attack the same. A shorter morphing region closer to the trailing edge is beneficial for generating larger lift coefficient with the same tendon moment and angle of attack. Flutter occurs with the increase of the air speed. When the morphing end position is fixed at 0.9 chord, increasing the morphing length reduces the critical flutter speed significantly, with the second bending mode tending to drive instability. With the same morphing length, moving the morphing region closer to the leading edge increases the critical flutter speed, and the unstable mode changes from the second mode into the first mode.

与传统的铰链襟翼相比,鱼骨主动凸面(FishBAC)气动翼片作为一种连续平滑的气动翼片变形概念,在气动效率方面有显著提高。本文为研究鱼骨式主动凸缘气膜的静态和动态气动弹性,开发了一个非稳态二维耦合流固耦合模型,其中包括鱼骨式主动凸缘脊柱、蒙皮、弦杆、腱和致动器的结构响应,并与一个非稳态空气动力学模型耦合。结构动态模型基于季莫申科梁理论,而空气动力学模型基于彼得斯非稳态模型。模型通过验证后,对静态和动态气动弹性进行了研究。结果表明,滑轮旋转角的增加会减小零升力攻角,同时保持升力系数与攻角之间的斜率不变。靠近后缘的较短变形区域有利于在相同的腱矩和攻角下产生较大的升力系数。随着气流速度的增加,会出现扑翼现象。当变形端位置固定在 0.9 弦处时,增加变形长度会显著降低临界扑翼速度,第二弯曲模式往往会导致不稳定。在变形长度相同的情况下,将变形区域移近前缘会增加临界扑翼速度,不稳定模式会从第二种模式变为第一种模式。
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引用次数: 0
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