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Analysis of periodic pulsating blood flow of fractional Maxwell power-law fluid in carotid artery with elastic vessel wall

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COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING 2024年第13期27卷 1845-1857页

作者： Zhang, Yan Peng, Yuan Gao, Jun Bai, Yu Sun, Dezhou Sun, Xiaopeng Lv, Bingbo Beijing Univ Civil Engn & Architecture Sch Sci Beijing Peoples R China Beijing Univ Civil Engn & Architecture Beijing Key Lab Funct Mat Bldg Struct & Environm R Beijing Peoples R China Shandong Univ Dept Neurosurg Dezhou Hosp Qilu Hosp Dezhou Peoples R China

Hemodynamic analysis reveals a highly significant effect on the prevention, diagnosis, and treatment of human vascular diseases. This article goes deeply into the periodic pulsatile blood flow in the carotid artery with an elastic vessel wall. In view of blood rheological experimental data, the constitutive equation of fractional Maxwell power-law fluid with yield stress, which can describe the four characteristics of yield stress, viscoelasticity, shear thinning, and thixotropy is established. Meanwhile, drawing support from the data of pulsatile flow, the finite Fourier series of pressure gradient with a period of 1 s has been proposed. Leading into Hooke's law can build the fluid-structure coupling boundary condition of blood flow and elastic vessel wall. The numerical solutions are got hold of finite difference method integrated with the newly developed L1-algorithm, and their convergence and stability of which are verified. The axial velocities of blood under different constitutive relationships are compared. The results throw light that other constitutive relationships underestimate the velocity of blood. Furthermore, the flow rate and wall shear stress on different fluid are calculated. It can be concluded that compared with Bingham fluid, the maximum and minimum flow rate/wall shear stress of fractional Maxwell power-law fluid with yield stress increases by 19% and 32%, respectively. The flow rate lags behind the pressure gradient and has time delay effect, on the contrary, the velocity of blood vessel wall is keeping pace with the pressure gradient. The effects of relevant physical parameters on velocity are discussed. In addition, the spatiotemporal distribution of blood flow in cerebral artery and femoral artery are analyzed.

关键词： pulsating blood flow fractional maxwell power-law constitutive elastic wall fluid-structure interaction finite differences

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Asynchronous parallel reinforcement learning for optimizing propulsive performance in fin ray control

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ENGINEERING WITH COMPUTERS 2024年 1-18页

作者： Liu, Xin-Yang Bodaghi, Dariush Xue, Qian Zheng, Xudong Wang, Jian-Xun Univ Notre Dame Dept Aerosp & Mech Engn Notre Dame IN 46556 USA Univ Maine Dept Mech Engn Orono ME 04469 USA Rochester Inst Technol Dept Mech Engn Rochester NY 14623 USA Cornell Univ Sibley Sch Mech & Aerosp Engn Ithaca NY 14853 USA

Fish fin rays constitute a sophisticated control system for ray-finned fish, facilitating versatile locomotion within complex fluid environments. Despite extensive research on the kinematics and hydrodynamics of fish locomotion, the intricate control strategies in fin-ray actuation remain largely unexplored. While deep reinforcement learning (DRL) has demonstrated potential in managing complex nonlinear dynamics;its trial-and-error nature limits its application to problems involving computationally demanding environmental interactions. This study introduces a cutting-edge off-policy DRL algorithm, interacting with a fluid-structure interaction (FSI) environment to acquire intricate fin-ray control strategies tailored for various propulsive performance objectives. To enhance training efficiency and enable scalable parallelism, an innovative asynchronous parallel training (APT) strategy is proposed, which fully decouples FSI environment interactions and policy/value network optimization. The results demonstrated the success of the proposed method in discovering optimal complex policies for fin-ray actuation control, resulting in a superior propulsive performance compared to the optimal sinusoidal actuation function identified through a parametric grid search. The merit and effectiveness of the APT approach are also showcased through comprehensive comparison with conventional DRL training strategies in numerical experiments of controlling nonlinear dynamics.

关键词： Off-policy RL Dynamic control Computational fluid dynamics fluid-structure interaction

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Self-Assembly of Lamellae by Elastocapillarity in the Presence of Gravity: Experiments and Modeling

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JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME 2024年第2期92卷 021004页

作者： Li, Chengzhang Tawfick, Sameh Univ Illinois Grainger Coll Engn Dept Mech Sci & Engn Urbana IL 61801 USA Univ Illinois Beckman Inst Adv Sci & Technol Urbana IL 61801 USA

Elastocapillarity describes the self-organization of elastic structures under liquid surface forces, for applications to micro- and nanoscale self-assembly. It has recently become evident that precise prediction of elastocapillary self-assembly is challenged by the various phenomena arising due to fluid flow. In this study, we present experiments and a corresponding reduced-order model for the dynamic coalescence of flexible lamellae arrays. Vertical arrays of elastomeric lamellae attached to a substrate at the bottom are fabricated using 3D-printed molds. The lamellae have sub-mm thickness and a few millimeters height, a size scale that cannot be achieved by traditional microfabrication. The gaps between the elastic lamellae are fi lled with liquid while the tips of the lamellae, which are at the top with respect to gravity, are initially fi xed, and then, they are released which leads to their spontaneous bending and coalescence. We study the cluster size as a function of system variables both experimentally and numerically. The solid lamellae are modeled as discrete rigid elements connected by torsional springs to the substrate, while the fluid flow uses lubrication theory and capillarity. Importantly, the model incorporates the gravitational forces to effectively capture the systems' behavior ranging from the microscale with negligible gravity effect to the macroscale where gravity significantly influences the dynamics. We further derive a linearized continuum model from our nonlinear formulation, providing an analytical universal scaling law for the lamellae cluster size. This work is relevant for new polymorphic fi ns and lamellae devices, capillary self-folding and origami.

关键词： elastocapillarity surface tension capillary effects fluid-structure interaction elastic deformation lubrication theory Bond number self-assembly dynamics

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

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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 1517-1517页

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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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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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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Influence of Chinstrap Stiffness on Cerebrospinal fluid Dynamics and Brain Stress in Helmet Impacts

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APPLIED SCIENCES-BASEL 2025年第10期15卷 5459-5459页

作者： Mayer, Jonathan Nasef, Daniel Bekbolatova, Molly Zwibel, Hallie Toma, Milan New York Inst Technol Coll Osteopath Med Dept Osteopath Manipulat Med Old Westbury NY 11568 USA New York Inst Technol Coll Osteopath Med Ctr Biomed Innovat Old Westbury NY 11568 USA

This study explores the influence of chinstrap stiffness in baseball helmets on brain stress distribution during high-velocity impacts through a computational biomechanical model integrating neuroanatomical structures and helmet components. Using a framework that combines finite element analysis and smoothed-particle hydrodynamics, this research evaluates fluid-structure interactions between cerebrospinal fluid, brain tissue, and six chinstrap configurations ranging from highly flexible to non-stretchable. The results reveal a critical trade-off: highly flexible straps reduce intracranial stress by dissipating energy through viscoelastic deformation but compromise helmet stability, while non-stretchable designs transmit undampened forces directly to the skull base, amplifying stress in vulnerable neurovascular regions. Intermediate stiffness configurations introduce a hazardous instability regime, where partial decoupling between the helmet and mandible causes lateral sliding of the chin guard, concentrating stresses at bony interfaces. The study identifies a nonlinear relationship between material rigidity and neuroprotection, emphasizing that optimal chinstrap design must balance elasticity to absorb impact energy with sufficient rigidity to maintain alignment and prevent stress redirection. Intermediate stiffness thresholds, despite partial energy absorption, paradoxically heighten risks due to incomplete coupling and dynamic instabilities. These findings challenge conventional helmet design paradigms, advocating for material engineering strategies that prioritize energy dissipation pathways while avoiding detrimental intermediate stiffness ranges. The insights advance concussion mitigation by refining chinstrap performance criteria to address both direct force transmission and instability-mediated injury mechanisms.

关键词： chinstrap stiffness helmet design brain stress distribution computational biomechanics concussion mitigation fluid mechanics fluid-structure interaction cerebrospinal fluid interaction

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Nonlinear vibrations of cantilevered circular cylindrical shells partially filled with liquid presenting large-amplitude sloshing

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2025年 233卷

作者： Moghaddasi, Hamid Reza Amabili, Marco Westlake Univ Sch Engn Hangzhou 310030 Zhejiang Peoples R China McGill Univ Dept Mech Engn Montreal PQ Canada

While fully numerical studies on nonlinear sloshing of liquids in various elastic and rigid containers exist, analytical studies on partially filled circular cylindrical elastic shells are limited to small-amplitude (linear) sloshing of the free liquid surface. In this study, for the first time, largeamplitude nonlinear vibrations of thin elastic shells, with clamped-free (cantilevered) boundary conditions, are coupled to large-amplitude sloshing liquid. The shell is modeled according to the Fl & uuml;gge-Lur'e-Byrne nonlinear shell theory. The liquid velocity potential satisfies the Laplace equation in the domain, and nonlinear boundary conditions are imposed at the free sloshing surface. Using the Lagrange multipliers method to satisfy the nonlinear boundary conditions for the liquid, the Lagrange equations of the system are made stationary. The effects of the liquid level inside the shell and nonlinearity at the free surface are investigated through frequency-response curves around resonances. It was observed that the sloshing nonlinearity often intensifies the softening behavior of the system in comparison to linear sloshing, and an increase in the liquid level inside the shell can have the same effect. Also, in contrast to some literature, it was found that there is a significant difference between considering nonlinear or linear sloshing during large amplitude vibrations of the shell, even when the free-surface oscillation amplitude is small.

关键词： Shell fluid-structure interaction Nonlinear sloshing Nonlinear vibrations Lagrange multipliers

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Design, aerodynamic performance and structural integrity investigations of aerofoil profiled Savonius vertical axis wind turbine

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JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING 2025年第3期47卷 1-38页

作者： Chandran, Sheeba Natarajan, Varshini Subramanian Doss, Arockia Roshan Anthony Madasamy, Senthil Kumar Arputharaj, Beena Stanislaus Rajendran, Parvathy Sourirajan, Laxana Nathan, Janani Priyadharshini Veeraperumal Senthil Raji, Arul Prakash Raja, Vijayanandh Kumaraguru Coll Technol Dept Aeronaut Engn Coimbatore 641049 Tamil Nadu India SIMATS Saveetha Sch Engn Dept Res & Innovat Chennai 602105 Tamil Nadu India Univ Sains Malaysia Sch Aerosp Engn Engn Campus Nibong Tebal 14300 Penang Malaysia

Wind energy is the suitable and sustainable sources of energy to fulfil the projected energy demands and to diminish the climate changes. Savonius vertical axis wind turbines (VAWT) are in fact the most appropriate energy producer for small-scale applications. However, the existing Savonius turbines are less efficient compared to other types of turbines. To achieve aerodynamically efficient blade design, optimal design parameters like aspect ratio, diameter, height, overlap ratio are identified. Ten different Savonius designs are modelled, and computational investigations are done using ANSYS Fluent and the outcomes are validated experimentally. The starting ability of the Savonius VAWT model is determined through static computational fluid dynamics analysis. The results revealed that conventional Bach Savonius produces 42.7% more static torque coefficient (CT) than the conventional semi-circular Savonius. The innovative two- and four-bladed, NACA 9407 imposed untwisted Savonius designs developed in this study provides 62.9% and 67.9% more static CT compared to the better-performing conventional Bach model. For material selection, the structural parameter investigations on two-bladed Bach and two-bladed NACA 9407 aerofoil imposed untwisted Savonius (hybrid model) turbine was executed based on two-way coupling fluid structural interaction (FSI) approach. From the structural analysis, it was found that the imposition of boron epoxy composite on the Bach and hybrid model provides lesser deformation, stress and strain when compared to the other materials. The hybrid model is found to be structurally efficient because it provides 96%, 35% and 37% lesser deformation, strain and stress compared to Bach model with boron epoxy composite.

关键词： Vertical axis wind turbine (VAWT) Computational fluid dynamics fluid-structure interaction Savonius VAWT Coefficient of torque

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