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FSI characteristics and structural stability of a large-size underwater robotic arm with various rigidity distribution

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OCEAN ENGINEERING 2025年 325卷

作者： Bian, Deyong Liu, Yuhong Yuan, Manxing Zhang, Hongwei Ma, Zhesong Zheng, Chao Tianjin Univ Key Lab Mech Theory & Equipment Design Minist Educ Sch Mech Engn Tianjin 300072 Peoples R China Wuhan Second Ship Design & Res Inst Wuhan 430205 Peoples R China

The complex marine environment poses significant challenges for the operational accuracy and the structural stability of the underwater robotic arms (URAs), especially for those large-size URAs with large movements. This paper investigates the hydrodynamic characteristics and structural deformation of a large-size URA with multiple parallel links (URA-MPL for short) through two-way fluid-structure interaction (FSI) method. The effect of different material combinations on the FSI characteristics and structural stability of the URA-MPL are especially discussed. The findings reveal that the elasticity modulus across different arm and link components significantly affects the URA-MPL's hydrodynamic forces and structural deformation. The structural stability of URA-MPL is higher when the rigidity of the upstream components is greater and that of the downstream components is smaller. The paper underscores the critical influence of material distribution on the dynamic response and stability of URA-MPL. The research results contribute to the optimal structural design of underwater robotic arms.

关键词： Underwater robotic arm Multiple parallel links Material elasticity modulus fluid-structure interaction Structural stability

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Dynamic responses of undamped oscillator subjected to underwater shock wave

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INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES 2025年 289卷

作者： Liang, Wen Liang, Minzu Chen, Rong Qi, Zizhen Zhang, Yuwu Li, Xiangcheng Lin, Yuliang Natl Univ Def Technol Coll Sci Changsha 410073 Peoples R China Natl Univ Def Technol Coll Adv Interdisciplinary Studies Changsha 410073 Peoples R China

The dynamic response of underwater structures subjected to shock waves is of great interest to the defense and oil industries. This work analyses the fluid-structure interaction (FSI) effects during dynamic response of an undamped oscillator consisting of a mass block and a spring when it exposed to underwater blast loading and develops a theoretical model for predicting the motion history of mass block. The spring-loaded valve is selected as a typical undamped oscillator structure and subjected to explosion loading in a water tank. The displacement histories of the valve spool supported by various springs at different proportional distances are measured, and the conversion process between work done by shock wave and the kinetic energy of the valve spool and potential energy stored in the spring is analyzed. A one-dimensional unsteady flow model is developed based on the basic relationship of shock wave and the Tait equation of state for water, which has better universality due to its consideration of the compressibility of water. Using this theoretical model, the influence of the characteristic parameters of the shock wave and the structural parameters of the undamped oscillator on the fluid-solid interface pressure, energy conversion, and the motion response of the mass block are analyzed. The study found that the work done by the shock wave on the undamped oscillator is mainly converted into the kinetic energy of the mass block;this kinetic energy is then converted into the elastic potential energy and dissipated energy. The conversion rate of shock wave energy is mainly influenced by the dimensionless FSI coefficient and is independent of the specific strength of the undamped oscillator. Based on the relationship between energy conversion rate and FSI coefficient, an analytical solution for the displacement of the mass block is derived, along with a criterion to determine whether the mass block can reach the constraint boundary. The research results provide a re

关键词： fluid-structure interaction Shock wave Undamped oscillator Energy conversion Displacement prediction Analytical solution

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Advanced numerical methods for conjugate heat transfer problems

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COMPUTERS & fluidS 2025年 292卷

作者： Errera, Marc-Paul Univ Paris Saclay DAAA NFLU ONERA F-92322 Chatillon France

Conjugate heat transfer (CHT) analysis is a simulation process that addresses the thermal interaction between a solid body and a fluid. It is a crucial aspect in a wide range of engineering applications, especially in the aerospace industry. This paper focuses on implementing adaptive coupling coefficients to optimize CHT by improving stability and simplicity. A mathematical model based on a normal mode stability analysis is employed. This study highlights the importance of a new dimensionless number, the "numerical Biot number", and explores adaptive coupling coefficients in three distinct aerothermal situations: steady coupling, steady coupling with radiation, and unsteady coupling. The main results of these three cases are compared, illustrated, and analyzed. The results demonstrate the potential of the theoretical approach, particularly in understanding the impact of different phenomena on the stability process and the challenges of convergence in certain conditions.

关键词： Computational methods Conduction Convection Radiation Conjugate heat transfer fluid-structure interaction Stability Convergence

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Reduced order model based on sound pressure frequency response function for modal parameter estimation

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SHIPS AND OFFSHORE structureS 2025年

作者： Liu, Jia Tang, Hu Li, Sheng Dalian Univ Technol Sch Naval Architecture & Ocean Engn State Key Lab Struct Anal Optimizat & CAE Software Dalian Peoples R China

A reduced-order method is proposed for estimating the modal parameters of structures. This method employs a matrix-free formulation of the rational Krylov projection. It constructs a reduced-order model by employing the transfer functions of the structure's near-field acoustic radiation at selected interpolation frequencies. The natural frequencies and modal damping ratios of the structure are derived from the eigenpairs of the reduced model, the computational cost is greatly reduced, and the valid range of the reduced model is discussed. The sound pressure transfer functions can be obtained from actual measurements, eliminating the need for the mass, stiffness, and damping matrices of the original system, which effectively mitigates errors introduced by simplifications and assumptions during the modelling process. Through tests of frequencies and modal damping ratios, non-physical modes introduced during the model simplification process are filtered out. The effectiveness of the method is validated through numerical examples.

关键词： Reduced-order model modal parameters acoustic radiation fluid-structure interaction

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Axial-flow-induced structural vibration in a 5x5 cylinder cluster

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NUCLEAR ENGINEERING AND DESIGN 2025年 431卷

作者： Lu, Zongyan Wang, Peng Zhou, Yu Harbin Inst Technol Ctr Turbulence Control Shenzhen Peoples R China Shanghai Jiao Tong Univ Sch Naval Architecture Ocean & Civil Engn Shanghai Peoples R China Eastern Inst Technol Coll Engn Sch Mech & Mech Engn Ningbo Peoples R China

This work aims to experimentally study the incident turbulence intensity T-u effect on the flow-induced vibration of an elastic cylinder positioned at the center of a 9- or 25-cylinder cluster subjected to an axial flow. T-u is examined at 0.71% - 0.80% and 2.30% - 2.91%. The pitch-to-diameter ratio P* is 1.36 similar to 1.64. Lateral vibrations along two orthogonal directions are simultaneously measured with the interstitial flow of the cylinder bundle. Two mechanisms are identified behind the elastic-cylinder vibration at low and high T-u. One is the presence of a varying velocity gradient within the cylinder bundle, and the other is incident flow fluctuations. At low T-u (0.71% - 0.80%), the root-mean-square vibration amplitude A(rms)* of the elastic cylinder exhibits strong dependence on the P* and cylinder number N. Increasing velocity gradient with decreasing P* or increasing N plays a key role in destabilizing the shear layers surrounding the elastic cylinder, inducing eddies to separate from the cylinder-wall and actively interact with those near the neighboring cylinder. Therefore, the near-wall velocity fluctuation u(rms)* and A(rms)* are increased. At high T-u (2.3% - 2.91%), A(rms)* is weakly dependent on P* compared with that at low T-u. It is found that the shear-layer instability surrounding the elastic cylinder is mainly intensified by the incident flow fluctuations with a higher T-u, accounting for the enhanced eddy activities, while the velocity-gradient effect associated with a change in P* is of less importance.

关键词： Cylinder bundle fluid-structure interaction Axial flow Flow-induced vibration Turbulence intensity

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Spectral behavior of a horizontal axis tidal turbine in elevated levels of homogeneous turbulence

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APPLIED ENERGY 2025年 380卷

作者： Hanzla, Mohd Banerjee, Arindam Lehigh Univ Atlantic Marine Energy Ctr Dept Mech Engn & Mech Bethlehem PA USA

Tidal turbines operate in elevated levels of freestream turbulence. The inflow turbulence affects the turbine performance and loading and drives the power fluctuations transmitted to the grid, necessitating costly synchronizers. Accounting for the role of turbulence parameters in generating turbine output fluctuations is vital for the optimal design of these devices. A detailed experimental campaign was conducted to study the power and thrust fluctuations of a 1:20 scaled turbine subjected to elevated turbulence;the results are compared to quasi-laminar low turbulence inflow conditions. In particular, we examine the effects of turbulence intensity, integral length scale, periodic structures, and tip-speed ratios on the turbine spectral response. Three distinct regimes of low, intermediate, and high frequency for the turbine power and thrust spectra are found, with differences mostly arising in the low and intermediate regions depending on the inflow condition. A transition from quasi-laminar to elevated turbulence inflow resulted in a steeper decay in the intermediate region, with f(-2) to f(-11/3) for turbine power and f(-1) to f(-8/3) for thrust. A larger integral length scale in the inflow extends the decay region to lower frequencies. However, unlike thrust, the power spectra exhibit a transition from f(-5/3) to f(-8/3) with an additional f(-11/3) region at higher tip-speed ratios. The turbine indicates strong signatures of the impact of periodic structures, which not only increases the fluctuations but can significantly enhance the fatigue loading of the blades, particularly for low-frequency periodic structures. Lastly, the study demonstrates the use of existing turbine spectral models for two different integral length scale regimes (L-u < < D and L-u similar to D) at varied tip-speed ratios.

关键词： Tidal stream turbine Power spectra Thrust spectra fluid-structure interaction Active grid

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Modal dynamic and response spectrum analyses of rectangular flexible water containing structures through modified ground motion accelerations

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ENGINEERING structureS 2025年 325卷

作者： Bouaanani, Najib Kouhdasti, Ramtin Polytech Montreal Dept Civil Geol & Min Engn Montreal PQ H3C 3A7 Canada

This article introduces a new approach for the assessment of the seismic behaviour of water containing structures such as storage tanks or navigation lock chambers. The novelty of the proposed approach lies in its integration of earthquake-induced water impulsive effects into a modified version of the input ground motion acceleration and its response spectrum. The modified time-history and spectral ground motion accelerations can then be directly applied to a numerical model of the empty container built using standard finite elements, thus eliminating the need for specialized software capable of modelling fluid domains and dynamic fluid- structure interactions. The formulation and procedures of the proposed methods are detailed and showcased through application to the seismic analysis of two illustrative examples of a rectangular water storage tank and an asymmetrical navigation lock chamber subjected each to two ground motion accelerations. The results are discussed to highlight how the proposed techniques effectively dissect hydrodynamic effects along the contributions of each vibration mode. Key parameters such as displacements, shear forces, and stresses are evaluated, and their modal and total responses compared to those corresponding to empty containers to assess earthquake-induced hydrodynamic effects. The proposed approach is shown to be in excellent agreement with classical coupled solid-fluid finite element solutions.

关键词： Water-containing structures Seismic response fluid-structure interaction Water-storage tanks Dynamic modal time-history analysis Response spectrum analysis Hydrodynamic pressure Finite elements

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High-Fidelity Aeroelastic Analysis of a Wind Turbine Using a Nonlinear Frequency-Domain Solution Method

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ENERGIES 2025年第5期18卷 1195-1195页

作者： Naung, Shine Win Rahmati, Mohammad Shine, Htet Univ West England Sch Engn Bristol BS16 1QY England Northumbria Univ Dept Mech & Construct Engn Newcastle Upon Tyne NE1 8ST England Capula Ltd Energy Dept Stone ST15 0LT England

This paper investigates the aeroelastic behaviour of a full wind turbine model with realistic blade vibration amplitude (9% span) using a nonlinear frequency-domain solution method. The primary objective is to demonstrate the computational efficiency of this method for an aeroelastic analysis compared to resource-intensive time-domain approaches. The underlying CFD model was validated against experimental data and benchmark simulations. The frequency-domain method was then validated against a conventional time-domain method, comparing aerodynamic damping and unsteady pressure distributions, with strong agreement observed. Results show a more complex unsteady pressure distribution at 324.5 RPM compared to 424.5 RPM, directly affecting aerodynamic damping. While aeroelastic stability was observed at both speeds, aerodynamic damping was significantly lower at 324.5 RPM. Flow field analysis reveals a clear relationship between relative velocity, static pressure, and blade vibration. Critically, the frequency-domain method achieved comparable accuracy to the time-domain method but with a significantly reduced computational cost (9 h versus 120 h), making it highly attractive for routine aeroelastic analyses and design optimisation.

关键词： wind turbines renewable energy aerodynamics aeroelasticity computational fluid dynamics fluid-structure interaction

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Boulder transport under mixed-lubrication friction

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EUROPEAN JOURNAL OF MECHANICS B-fluidS 2025年 111卷 120-126页

作者： DuBerry-Mahon, J. Herterich, J. G. Univ Coll Dublin Sch Phys Dublin Ireland Univ Coll Dublin Sch Math & Stat Dublin Ireland Univ Coll Dublin Earth Inst Dublin Ireland

Boulder transport by wave action may exploit thin gaps between the boulder and bedrock platform whereby a lubrication zone reduces the friction coefficient during sliding. We derive an effective mixed-lubrication friction coefficient, depending on boulder speed and the geometry of the lubricated region, and analyse its effect on boulder transport. Mixed lubrication enhances boulder dynamics when moving at a faster speed, the lubricated region is increased, or with fewer separated lubricated regions and smaller boulder aspect ratios. We compare our model against static friction and an empirically-fitted model.

关键词： Boulder transport Friction Lubrication fluid-structure interaction Mathematical modelling

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Exploring the swimming performance and the physical mechanisms of Tomopteris locomotion

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BIOINSPIRATION & BIOMIMETICS 2025年第2期20卷 026011-026011页

作者： Battista, Nicholas A. Coll New Jersey Dept Math & Stat 2000 Pennington Rd Ewing Township NJ 08628 USA

Tomopterids are mesmerizing holopelagic swimmers. They use two modes of locomotion simultaneously: drag-based metachronal paddling and bodily undulation. Tomopteris has two rows of flexible, leg-like parapodia positioned on opposite sides of its body. Each row metachronally paddles out of phase to the other. Both paddling behaviors occur in concert with a lateral bodily undulation. However, when looked at independently, each mode appears in tension with the other. The direction of the undulatory wave is opposite of what one may expect for forward (FWD) swimming and appears to actively work act against the direction of swimming initiated by metachronal paddling. To investigate how these two modes of locomotion synergize to generate effective swimming, we created a self-propelled, fluid-structure interaction model of an idealized Tomopteris. We holistically explored swimming performance over a 3D mechanospace comprising parapodia length, paddling amplitude, and undulatory amplitude using a machine learning framework based on polynomial chaos expansions. Although undulatory amplitude minimally affected FWD swimming speeds, it helped mitigate the larger costs of transport that arise from either using more mechanically expensive (larger) paddling amplitudes and/or having longer parapodia.

关键词： Tomopteris polychaete swimming fluid-structure interaction generalized polynomial chaos expansions suction thrust performance trade-offs global sensitivity analysis

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