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Data-Driven Identification of Variational Equations for Vortex-Induced Vibration Systems

JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME 2025年第4期92卷 041001页

作者： Lu, Kang Zeng, Zheng Xiong, Xiong Wang, Xuefeng Gu, Xudong Hu, Rongchun Deng, Zichen Northwestern Polytech Univ Dept Engn Mech MIIT Key Lab Dynam & Control Complex Syst Xian 710129 Peoples R China

In this study, a data-driven approach using the embedded variational principle is used to identify the variational equations of vortex-induced vibration fluid-structure interaction systems, in particular the coupling term and the aerodynamic damping term. Under the data-driven paradigm, variational equation identification is primarily accomplished through five steps: collecting discrete data, setting variational functions, building the product function, solving linear equations, and evaluating errors. The explicit variational equations of the system are eventually determined automatically from the excitation and response. Gaussian white noise is added to the excitation to evaluate the method's noise robustness. The findings demonstrate that numerical estimation which stays away from higher-order derivatives significantly enhances the variational law identification's noise robustness by taking advantage of the variational law's lower-order time derivatives. Furthermore, the arbitrariness of the variational setting inherent in the variational law significantly improves the effectiveness of data utilization and lowers the necessary data volume. In addition, a system of linear equations is solved by identifying connected nonlinear equations, which significantly increases modeling efficiency. The basis for engineering modeling, optimization, and control of intricate fluid-structure interaction systems are provided by these benefits.

关键词： data-driven system identification vortex-induced vibration fluid-structure interaction variational principle dynamics

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Application of a Coupled Eulerian-Lagrangian Approach to the Shape and Force of Scientific Balloons

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APPLIED SCIENCES-BASEL 2025年第3期15卷

作者： Kong, Lingsen Yang, Yanchu Cai, Rong Zhang, Hangyue Lyu, Weihao Chinese Acad Sci Aerosp Informat Res Inst Beijing 100094 Peoples R China Univ Chinese Acad Sci Beijing 100190 Peoples R China

Scientific balloons provide an inexpensive and reliable platform for near-space scientific experiments. The analysis of the balloon geometry and forces has always been a major concern for balloon designers. Most previous studies have focused solely on the fully inflated shapes and forces of balloons, analyzing only the membrane structure and simplifying the effects of internal and external gases into a gradient pressure difference. This approach lacks consideration of the fluid-structure interaction (FSI) of scientific balloons. This paper utilizes the Coupled Eulerian-Lagrangian (CEL) method in the Abaqus/Explicit simulation environment to analyze the FSI effects of scientific balloons under the influence of internal helium and external air. Three typical working conditions of scientific balloons are selected for simulation analysis. First, a three-dimensional spherical balloon is simulated during the ascent process to verify the correctness of the CEL simulation framework. This also demonstrates the membrane folding characteristics during balloon ascent, which could not be calculated in previous two-dimensional axisymmetric simulations. Next, the study explores balloon shapes that deviate from quasi-static pressure distributions due to the motion of internal helium. These include the "mushroom" shape observed during the dynamic launching of the balloon on the ground and the "sail" shape caused by lateral airflow. The mushroom shape arises from the sudden loss of the bottom constraint, causing the internal helium to move upward while being resisted by the air at the balloon's top. The simulation successfully replicates the rapid waist transition and the downward concavity at the top due to air resistance, while also providing the corresponding force distribution. For the sail-shaped condition, the simulation analyzes the balloon's tilt angle and the characteristic upturn of its windward surface. By a comparison with no-wind conditions, this study quantifies the imp

关键词： scientific balloon fluid-structure interaction CEL method dynamic balloon shape sail shape

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Dynamics and thrust performance of a modeled multifoil wave-induced flapping foil propulsor

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OCEAN ENGINEERING 2025年 317卷

作者： Raut, Harshal S. Seo, Jung-Hee Mittal, Rajat Johns Hopkins Univ Dept Mech Engn Baltimore MD 21218 USA

Wave-assisted propulsion (WAP) systems directly translate wave energy into thrust for a surface vessel by employing free-to-pitch hydrofoils suspended under the vessel. In multi-foil WAP propulsors, the trailing foils can use the wake of the leading foils in order to improve their thrust performance and we use a simple phenomenological model to predict the thrust performance of the trailing foil in a two-foil WAP propulsor. Next, we perform direct numerical simulations to examine the effect of three key parameters on the flow physics, the fluid-structure interaction, as well as the thrust performance of these systems - the streamwise and cross-stream distance between the two foils and the Strouhal number. To quantify the mechanisms associated with thrust generation, the force-partitioning method (FPM) is used, which decomposes the pressure forces into interpretable components. Based on the results of the two-foil system, optimal three-foil and four-foil systems are also examined. The study demonstrates how insights from flow physics can be used to guide the design of high-performing wave-assisted propulsion systems.

关键词： Wave assisted propulsion Heaving and pitching hydrofoil Immersed boundary method fluid-structure interaction Multi-foil propulsion system

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Dynamic response and damage collapse of bridge subjected to debris flow impacts using coupled Eulerian Lagrangian method

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ADVANCES IN STRUCTURAL ENGINEERING 2025年

作者： Fan, Jian Wu, Zhifeng Gao, Chunyang Lu, Yang Li, Yuan Huazhong Univ Sci & Technol Sch Civil & Hydraul Engn Wuhan Peoples R China Wuhan Inst Technol Sch Civil Engn & Architecture 693 Xiongchu Ave Wuhan 430073 Hubei Peoples R China

The coupled Eulerian Lagrangian (CEL) fluid-structure interaction method was employed to study the bridge's dynamic behaviour under debris flow. The accuracy of the numerical simulations using the CEL method was confirmed by comparing them with small-scale experimental results for debris flow impacting bridge piers. For a real continuous girder bridge susceptible to debris-flow disasters, a detailed finite-element model of the bridge was established, with an emphasis on the precise modelling of hollow thin-walled variable-section piers. Utilising the CEL method, the study explored the effects of debris flow with varying burst frequencies on the bridge. The process of debris flow impacting bridge pier can be summarized into four stages: 'contact', 'flow around', 'closure', and 'stabilisation'. Prior to reaching the stabilisation stage, the stress near the flow-passing surface at the bottom of the pier gradually increases. The erosion effect of debris flow on the pier was further taken into consideration, distinguishing it from the simplified method of direct impact, as recommended in the standard. The CEL method provides a more precise representation of local damage and structural response in bridges under debris flow impact compared to the simplified method. During the impact under once-in-100-year debris-flow, the lower part of the pier experienced concrete damage and exposed steel bars, yet still maintained normal functionality. The study not only elucidated the effects of debris flow on the flow field distribution, stress, impact, displacement, and overall damage to the bridge but also highlighted vulnerable points within the bridge. The bridge appeared to meet operational requirements for a design lifespan of 100 years, but it may potentially collapse during once-in-200-year debris-flow. Under the once-in-200-year working condition, the weak point at the bottom of the pier, that is, the hollow solid conversion place, is first damaged, and further expands under t

关键词： bridge pier debris flow impacts coupled Eulerian Lagrangian fluid-structure interaction erosion effect damage collapse

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Numerical simulation of the oblique water impact of double curvature bodies involving suction and cavitation phenomena

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JOURNAL OF fluidS AND structureS 2025年 135卷

作者： Goron, M. Tassin, A. Langrand, B. Spinosa, E. Del Buono, A. Jacques, N. Fourest, T. Iafrati, A. DMAS ONERA F-59014 Lille France ENSTA Bretagne UMR CNRS 6027 IRDL F-29806 Brest 09 France Ifremer RDT F-29280 Plouzane France CNR INM Via Vallerano 139 I-00128 Rome Italy

The present study aims to assess the capability of a numerical method to model hydrodynamic impacts representative of an aircraft ditching. The considered numerical method is based on the Finite Element explicit solver Radioss and a Coupled Eulerian-Lagrangian approach. The fluid-structure interaction is dealt with using an immersed contact interface and a penalty coupling method. The oblique water impacts of three different fuselage sections have been studied based on the experimental campaigns carried out during the European project SARAH at the High-Speed Ditching Facility of CNR-INM in Rome, Italy. The results are presented in terms of force coefficient, local relative pressure, and free surface elevation. The effect of the coupling stiffness and size of the fluid elements on the numerical results is analysed to assess the robustness of the numerical method. The numerical method shows a satisfying capability to reproduce most of the experimental results. Particular attention is given to the capability of the numerical method to describe the suction and cavitation phenomena. The effect of the specimens' transversal cross-section, the specimens' longitudinal curvature and the development of cavitation phenomenon on the hydrodynamic loads are also investigated.

关键词： Numerical simulation fluid-structure interaction Coupled Eulerian-Lagrangian approach Aircraft ditching Suction Cavitation

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Nonlinear dynamic analysis of a novel tangentially supplied aerostatic bearing-rotor system: Theory and experiment

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2025年 224卷

作者： Qiu, Shun Ke, Changlei Li, Kongrong Zhang, Xiaohua Peng, Nan Liu, Liqiang Chinese Acad Sci Key Lab Cryogen Sci & Technol Tech Inst Phys & Chem Beijing 100190 Peoples R China Univ Chinese Acad Sci Beijing 100039 Peoples R China

The aerostatic bearing-rotor system plays a critical role in ensuring the stable operation of highspeed, high-precision rotating machinery. Despite its importance, the system is often affected by nonlinear sub-synchronous vibration instabilities, which limit its performance and development. To address this issue, this study proposes a novel tangentially supplied (TS) bearing. Modified gas lubrication Reynolds equations are derived, and a fluid-structure interaction model for the gas bearing-rotor system is established. By predicting gas film thickness distribution, the bearing lubrication equations and rotor motion equations are solved simultaneously. The nonlinear dynamics of the system are analyzed using bifurcation diagrams, rotor center orbits, and frequency spectrum plots, with comparisons to conventional radially supplied (RS) bearing. The results reveal differences in gas film pressure distribution, where the tangentially supplied bearing demonstrates slightly reduced load capacity but significantly suppresses sub-synchronous vibrations. Additionally, it raises both the bifurcation onset speed and the instability threshold speed, thereby improving system stability. Finally, theoretical predictions are validated through speedup and coast-down experiments.

关键词： Tangentially supplied aerostatic bearing Modified Reynolds equations fluid-structure interaction Nonlinear dynamic analysis

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An enhanced SPH-based hydroelastic FSI solver with structural dynamic hourglass control

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JOURNAL OF fluidS AND structureS 2025年 135卷

作者： Zhan, Yi Luo, Min Khayyer, Abbas Zhejiang Univ Ocean Coll Zhoushan 316021 Zhejiang Peoples R China Kyoto Univ Dept Civil & Earth Resources Engn Kyoto 6158540 Japan

This paper presents an enhanced hydroelastic FSI (fluid-structure interaction) solver based on the open-source SPH (Smoothed Particle Hydrodynamics) code DualSPHysics+. For the structure model, a second-order discretization of the deformation gradient tensor (F2nd) is implemented to improve the accuracy of stress and strain computation. To mitigate numerical noises in the reproduced stress fields and improve numerical stability, a Riemann Stabilization (RS) term is incorporated in the structural momentum equation. A Dynamic Hourglass Control (DHGC) scheme being parameter-free is proposed to mitigate the spurious zero-energy modes linked with rank deficiency as a challenging issue for collocated computational methods including the total Lagrangian SPH. The novelty of this scheme is that it dynamically adjusts the hourglass control coefficient based on the instantaneous state of particle distributions and time evolution of an error function. For the fluid model, the Velocity divergence Error Mitigating (VEM) scheme and Hyperbolic/Parabolic Divergence Cleaning (HPDC) scheme are adopted to suppress spurious fluid pressure noises and hence enhance the modelling of fluid-structure interactions. Validations in terms of robustness and accuracy of the proposed model are carried out via five structure examples and three FSI ones. The results demonstrate that more physically consistent stress and strain fields are reproduced by the implementation of F2nd and RS. The proposed DHGC scheme effectively suppresses hourglass modes and is case- and resolutionindependent (in contrast to the traditional Hourglass Control scheme). The incorporation of the VEM and HPDC mitigates fluid pressure noises and further enhances the accuracy of FSI simulations.

关键词： Dualsphysics plus Smoothed particle hydrodynamics Total lagrangian SPH Hourglass control fluid-structure interaction

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Prediction for Global Whipping Responses of a Large Cruise Ship Under Unprecedented Sea Conditions Using an LSTM-Based Encoder-Decoder Model

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JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING-TRANSACTIONS OF THE ASME 2025年第2期147卷 021401页

作者： Liu, Ruixiang Li, Hui Ong, Muk Chen Zou, Jian Harbin Engn Univ Coll Shipbldg Engn Harbin 150001 Peoples R China Univ Stavanger Dept Mech & Struct Engn & Mat Sci N-4036 Stavanger Norway

Global whipping responses contribute to a significant increase in vertical bending moments (VBM), making their accurate prediction crucial for ship safety. In this study, a long short-term memory (LSTM)-based encoder-decoder model is established to predict the whipping responses under varying sea states. The model is trained on a comprehensive dataset, which includes motion data and VBM history of a cruise ship under various sea conditions. This dataset is established via numerical simulation, ensuring a wide range of scenarios for the model to learn from. The efficacy of the LSTM encoder-decoder model in capturing global whipping responses is initially verified under a single sea condition case. This step confirms the model's ability to accurately predict vertical bending moments under known conditions. Subsequently, the model's performance under unprecedented sea conditions is examined. Given that the distribution of training data significantly influences the model's performance and the data from diverse sea conditions typically exhibit distinct data distribution, a mixed data training strategy is employed during the training process in this scenario. The results indicate that the LSTM encoder-decoder model effectively captures whipping responses. Furthermore, the mixed data training strategy significantly improves the model's prediction accuracy for global whipping responses under unprecedented sea conditions.

关键词： multivariate time series forecasting whipping response machine learning dynamics of structures fluid-structure interaction structural safety and risk analysis

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Finite element method analysis of flutter: Comparing Scott-Vogelius and Taylor-Hood elements

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JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS 2025年 469卷

作者： Vacek, Karel Svacek, Petr Czech Acad Sci Inst Math Zitna 25 Prague 1 Czech Republic Czech Tech Univ Fac Mech Engn Dep Tech Math Karlovo Nam 13 Prague Czech Republic

This paper focuses on the numerical simulation of the fluid-structure interaction (FSI) problem of an incompressible flow and a vibrating airfoil. The fluid flow is governed by the incompressible Navier-Stokes equations. The finite element method (FEM) is employed for the discretization of the weak form of equations. The main attention is paid to comparison of performance for different choices of finite element spaces together with a proper stabilization method. Two choices of the couple of finite element spaces are considered for velocity-pressure approximations. The first one is the standard Taylor-Hood finite element, the second one is the Scott-Vogelius element consisting of continuous piecewise quadratic velocities combined with discontinuous piecewise linear pressures. The barycentric refined mesh is used for the case of the Scott-Vogelius element in order to satisfy the Babu & scaron;ka-Brezzi inf-sup condition. The finite element approximations further require additional stabilization of the dominating convection. Here, the performance of the stream-line upwind Petrov-Galerkin (SUPG) stabilization, the SUPG together with the grad-div stabilization, the streamline-diffusion/local-projection stabilization approach is tested. The numerical results are presented and compared with the available data.

关键词： Navier-Stokes equation Finite element method fluid-structure interaction Taylor-Hood element Scott-Vogelius element

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fluid-induced vibration response characteristics of the oxygen pump volute

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JOURNAL OF VIBRATION AND CONTROL 2025年

作者： Huo, Shihui Xie, Bin Li, Ruizhi Zhang, Ping Natl Key Lab Aerosp Liquid Prop Xian 710100 Peoples R China Beihang Univ Sch Astronaut Beijing Peoples R China

The oxygen pump constitutes a crucial and intricate component within liquid rocket engines, serving as a primary source of engine vibration. This study delves into the unsteady fluid-induced excitation loading, considering the interplay between gap flow and main flow. The findings are validated through testing on a liquid rocket engine. Modal characteristics of the oxygen pump under varying liquid mediums are examined. The Rayleigh damping parameter is determined, accounting for the frequency characteristics of fluid-induced excitation, thereby establishing a comprehensive transient dynamic model. Subsequently, the transient dynamic response of the volute in an oxygen pump to unsteady fluid-induced excitation is analyzed, unveiling both time-domain and frequency-domain vibration response characteristics. The analysis methodology is corroborated through comparison with the statistical distribution of test results. Notably, the vibration response of the oxygen pump volute predominantly exhibits frequency doubling of rotational speed, with prominent occurrences observed at the 12X and 18X frequencies.

关键词： Unsteady fluid-induced excitation oxygen pump volute fluid-structure interaction vibration response statistical distribution

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