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Comprehensive numerical study on the behavior of floating structures under challenging ocean conditions using WCSPH

JOURNAL OF fluidS AND structureS 2025年 133卷

作者： Ramezanzadeh, Shayan Ozbulut, Murat Yildiz, Mehmet Ozyegin Univ Fac Aviat & Aeronaut Sci Istanbul Turkiye Sabanci Univ Fac Engn & Nat Sci TR-34956 Istanbul Turkiye Sabanci Univ Integrated Mfg Technol Res & Applicat Ctr TR-34956 Istanbul Turkiye Sabanci Univ Kordsa Composite Technol Ctr Excellence Istanbul Technol Dev Zone TR-34906 Istanbul Turkiye Altair Engn GmbH D-85748 Munich Germany

The main objective of this study is to investigate the dynamic motions of floating bodies under different wave conditions. A particle-based numerical method, Smoothed Particle Hydrodynamics (SPH), is used due to its capabilities in modeling violent free surface flows. This work is based on five sub-steps. The first step focuses on ensuring the accuracy of the generated wave characteristics. Then, the heave motion of a point-absorber wave energy converter is examined under regular wave conditions with different power take-off (PTO) damping coefficients. After validating the proposed SPH scheme in a single degree of freedom motion, the roll decay of a rectangular floating body is investigated in the third step by comparing natural frequencies and damping coefficients with available literature data. Subsequently, the roll motion of a fixed floating structure under a wide-range regular wave system is simulated to obtain the corresponding Response Amplitude Operators (RAOs). Finally, the free body motion of a floating body under regular wave excitation is simulated and validated by experimental measurements, considering all rotational and translational motion characteristics. In the light of all simulation results, the proposed SPH numerical scheme can be considered as a useful tool for the design of effective and sustainable offshore structures.

关键词： Weakly compressible smoothed particle hydrodynamics fluid-structure interaction Point-absorber wave energy converter Offshore hydrodynamics

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Dynamics of a two-phase bubble near a kinematic elastic-plastic boundary

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INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES 2025年 287卷

作者： Dong, Yifan Han, Wei Li, Rennian Nan, Haozhi Shen, Xiaobo Yang, Shiqi Bai, Lu Hou, Yuyan Lanzhou Univ Technol Coll Energy & Power Engn Lanzhou 730050 Peoples R China Lanzhou Univ Technol Adv Technol Res Inst Jiuquan Jiuquan 735000 Peoples R China Lanzhou Univ Technol Key Lab Adv Pumps Valves & Fluid Control Syst Minist Educ Lanzhou 730050 Peoples R China

Traditional underwater explosion bubble dynamics research, based on the point-source detonation assumption, typically regards bubbles as regular spheres. However, in applications such as underwater directional damage and bubble detection, deformed high-pressure bubbles demonstrate greater potential. This study introduces a novel scientific interest: the dynamics of two-phase deformed bubbles. Based on a charge structure encapsulated by a two-phase fluid layer, a bidirectional fluid-structure interaction numerical scheme is employed to systematically investigate the interactions between two-phase bubbles and a moving elasto-plastic structure. The findings reveal that, due to the impedance mismatch between the TNT and air media, a portion of the shock energy is redirected into the bubble interior as reflected waves at the TNT-air interface. This process effectively enhances the bubble's volumetric potential energy and lifespan, while inducing lagging wave effects on the opposite side. The non-uniform distribution of the two-phase medium inside the bubble alters its anisotropic compressibility, causing regions with higher compressibility to collapse more rapidly and triggering the re-entrant jets. This represents a novel mechanism of re-entrant jet induction, primarily driven by the anisotropic compressibility of the two-phase medium within the bubble. This mechanism exhibits distinct physical characteristics compared to the pressure-driven jet formation observed in traditional bubble dynamics. Moreover, it is weakly to boundary conditions, demonstrating strong independence. Compared to spherical bubbles, two-phase bubbles display a greater variety of mechanisms for imposing extreme loads on structures, including re-entrant jet loading, high-energy contact loading, and impulsive loading. The loads exerted by these bubbles result in three distinct structural deformation modes. These findings provide anew perspective on the dynamics of bubble-structure interactions and o

关键词： Underwater explosion fluid-structure interaction Shock wave Re-entrant jet Bubble dynamic

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Mode split prediction for rotating disks with flexible stator coupling

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JOURNAL OF fluidS AND structureS 2025年 132卷

作者： Berthet, Lucas Blais, Philippe Nennemann, Bernd Monette, Christine Gosselin, Frederick P. Polytech Montreal Mech Engn Dept Lab Multiscale Mech LM2 Montreal PQ Canada Andritz Hydro Canada Inc Pointe Claire PQ Canada

High-head turbine runners are subject to multiple sources of excitation. Coupled with the added mass of water, rotation induces a mode split in the natural frequencies of runners, where co- rotating and counter-rotating waves travel through the runner at different relative speeds. Disks, by displaying a similar behavior, can be used as a geometrically simpler model. Mode split is characterized for a rotating disk in dense fluid but, in high-head turbines, the runner and the compliant confinement are coupled through the axial gap fluid. In this article, we develop an analytical model of coupled stationary and rotating disks to analyze the effect of their interaction on the mode split phenomenon. First, we apply the potential flow theory, considering the fluid as irrotational, inviscid and incompressible. We assume that the modeshapes of the disk in a dense fluid are similar to their shapes in vacuum. We then derive the potential flows that respect the no-penetration boundary conditions. One after the other, each disk is considered flexible while the other one is rigid. By applying the superposition principle, we then couple the two obtained fluid flows through the structural equations of motion. A finite- element vibro-acoustic modal analysis was developed to verify the analytical model and propose a fast numerical tool for hydraulic turbine design. Analytical results show that rotation induces a split of the coupled rotor-stator frequencies as for a lone rotor, while the ratio of their amplitudes varies slightly. A change in the relative thickness of the rotor and stator affects their individual frequencies in vacuum, and in turn their coupling by the fluid, with a potential shift in dominance.

关键词： Hydraulic turbines fluid-structure interaction Rotor-stator coupling Mode split

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Mechanisms of aortic dissection: From pathological changes to experimental and in silico models

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PROGRESS IN MATERIALS SCIENCE 2025年 150卷 101363页

作者： Rolf-Pissarczyk, Malte Schussnig, Richard Fries, Thomas-Peter Fleischmann, Dominik Elefteriades, John A. Humphrey, Jay D. Holzapfel, Gerhard A. Graz Univ Technol Inst Biomech Graz Austria Univ Augsburg High Performance Sci Comp Augsburg Germany Graz Univ Technol Inst Struct Anal Graz Austria Stanford Univ Dept Radiol 3D & Quantitat Imaging Lab Stanford CA USA Yale Univ Sch Med Aort Inst New Haven CT USA Yale Univ Dept Biomed Engn New Haven CT USA Norwegian Univ Sci & Technol NTNU Dept Struct Engn Trondheim Norway

Aortic dissection continues to be responsible for significant morbidity and mortality, although recent advances in medical data assimilation and in experimental and in silico models have improved our understanding of the initiation and progression of the accumulation of blood within the aortic wall. Hence, there remains a pressing necessity for innovative and enhanced models to more accurately characterize the associated pathological changes. Early on, experimental models were employed to uncover mechanisms in aortic dissection, such as hemodynamic changes and alterations in wall microstructure, and to assess the efficacy of medical implants. While experimental models were once the only option available, more recently they are also being used to validate in silico models. Based on an improved understanding of the deteriorated microstructure of the aortic wall, numerous multiscale material models have been proposed in recent decades to study the state of stress in dissected aortas, including the changes associated with damage and failure. Furthermore, when integrated with accessible patient-derived medical data, in silico models prove to be an invaluable tool for identifying correlations between hemodynamics, wall stresses, or thrombus formation in the deteriorated aortic wall. They are also advantageous for model-guided design of medical implants with the aim of evaluating the deployment and migration of implants in patients. Nonetheless, the utility of in silico models depends largely on patient-derived medical data, such as chosen boundary conditions or tissue properties. In this review article, our objective is to provide a thorough summary of medical data elucidating the pathological alterations associated with this disease. Concurrently, we aim to assess experimental models, as well as multiscale material and patient data-informed in silico models, that investigate various aspects of aortic dissection. In conclusion, we present a discourse on future perspective

关键词： Aortic dissection Microstructure Morphology Material characterization Computational modeling Computational mechanics fluid-structure interaction Damage mechanics Hemodynamics Computational fluid dynamics Patient-specific simulation

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Investigating a hermetic reciprocating compressor performance under variable lift limiter height using FSI method

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART E-JOURNAL OF PROCESS MECHANICAL ENGINEERING 2024年

作者： Bacak, Aykut Pinarbasi, Ali Dalkilic, Ahmet Selim Yildiz Tech Univ Fac Mech Engn Dept Mech Engn Istanbul Turkiye Yildiz Tech Univ Fac Mech Engn Dept Mech Engn TR-34349 Istanbul Turkiye

This study examines discharge line energy losses using advanced fluid-structure interaction methods to show how valve design parameters-length, thickness, and height-improve compressor performance. An innovative 3D fluid-structure interaction model represents a self-acting hermetic reciprocating compressor's discharge valve as a beam element. The RNG k-epsilon model examines how reed valve thickness, length, compressor speed, and lift limiter height impact pressure pulsation and compressor efficiency. Under ASHRAE conditions, operating at a challenging temperature range of 54.4 to -23.3 degrees C, the study meticulously explores the intricate interplay of discharge valve characteristics. Specifically, varying valve thicknesses (0.127, 0.152, 0.178, and 0.2 mm) and lengths (14.722, 16.222, and 17.722 mm) are examined in conjunction with different compressor speeds (1300, 2100, and 3000 rpm) according to the design specifications. Upon meticulous examination of discharge line losses at a compressor speed of 1300 rpm, intriguing insights emerged. For lift limiter heights of 0.8, 1.05, and 1.25 mm, coupled with a valve length of 17.722 mm, the study unveiled remarkable average energy losses of -6.91%, 2.83%, and -8.52%, respectively. The exploration continued at 2100 rpm, revealing a dynamic pattern with average losses for the same lift limiter heights at 0.94%, -1.26%, and -4.43%, respectively. In a succinct summary, the valve in focus demonstrated a noteworthy disparity in discharge line losses, reaching a maximum variation of 9.15%, -3.83%, and -8.30% when operated at the challenging speed of 3000 rpm.

关键词： Hermetic reciprocating compressor fluid-structure interaction reed valve beam modeling discharge line

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A poroelastic δ-SPH model for modeling biofilm deformation and sloughing in microfluidic channels

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COMPUTERS AND GEOTECHNICS 2024年 175卷

作者： Feng, Dianlei Neuweiler, Insa Tongji Univ Shanghai 200092 Peoples R China Leibniz Univ Hannover D-30167 Hannover Germany

We present a poroelastic fluid-structure interaction delta-SPH model for simulating biofilm deformation and sloughing in microfluidic channels. Based on the mixture theory, this model accurately handles large deformations of solid structures and simultaneously simulates seepage flow within the porous biofilm and external flow. A key advantage of the model is its reliance on the solid phase material properties rather than the averaged properties of the biofilm, enabling the modeling of changes in porosity and biofilm material properties induced by loads. Model verification is achieved through two benchmark problems, followed by application to biofilm deformation and sloughing studies. The Young's modulus of biofilms is a key parameter of interest in many studies. Calibration of the biofilm's solid material elasticity modulus by using the presented model yields a value of 200 Pa, aligning with previous reports in literature. Additionally, the model is capable of simulating the sloughing process by evaluating local von Mises equivalent stress, reproducing different detachment patterns corresponding to various material strengths. This delta-SPH model offers an efficient numerical tool for biofilm analysis and is extendable to simulate other fluid-structure interaction problems involving porous media with large deformations, such as soil, debris flow, and biological tissues.

关键词： Biofilm Sloughing SPH Poroelastic Numerical modeling fluid-structure interaction

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Modeling Green Water Load on a Deck Mounted Circular Cylinder

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JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING-TRANSACTIONS OF THE ASME 2024年第3期146卷 031203-031203页

作者： Gao, Min Draper, Scott McCauley, Guy Chen, Lifen Zhang, Xiantao Wolgamot, Hugh Taylor, Paul H. Cheng, Liang Univ Western Australia Oceans Grad Sch Perth Australia Univ Western Australia Oceans Grad Sch Sch Engn Perth Australia Dalian Univ Technol State Key Lab Coastal & Offshore Engn Dalian 116024 Peoples R China Shanghai Jiao Tong Univ State Key Lab Ocean Engn Shanghai Peoples R China Univ Western Australia Sch Engn Perth Australia

This article uses scaled physical and numerical modeling to investigate an idealized but complicated problem in which green water impacts a circular cylindrical structure located on top of a fixed box representative of a vessel. A focused wave group was used to overtop the box and generate the green water event, which resembled a plunging wave with air entrainment. The plunger collapsed and ran across the deck before impacting and then scattering from the cylinder. To test the adequacy of the physical modeling, nominally identical experiments were conducted in two different laboratories, in different countries. The numerical modeling comprised computational fluid dynamics (CFD) simulations performed using openfoam. The flow features, the force on the cylinder, and the surface elevation on top of the box are compared in detail across the two physical models and the CFD. Consistent load measurements were obtained from the two physical model tests, with force impulse results differing by less than 10%, underscoring the validity of the results, even accounting for the complexity of flow-structure interactions. A comparison with numerical model results reveals some sensitivity to experimental precision in the flow measurements on top of the box and the green water load. Nonetheless, the overall force impulse discrepancy between experiments and numerical models is within 15%, highlighting that the robustness of the methods was used despite these sensitivities. The sensitivity to CFD mesh and iterating the incident wave to match CFD and experiment are also explored. The agreement between experiment and CFD serves as an example of the utility of CFD for modeling green water loads.

关键词： computational fluid dynamics fluid-structure interaction green water circular cylinder hydrodynamics

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Dynamic behavior and simplified analysis of bridge structures subjected to water-driven vessel collisions

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OCEAN ENGINEERING 2024年 313卷

作者： Fan, Wei Hu, Longkang Ye, Xudong Wu, Qinglin Chen, Bo Hunan Univ Coll Civil Engn Key Lab Wind & Bridge Engn Hunan Prov Changsha 410082 Peoples R China Univ Chongqing Res Inst Hunan Chongqing 401120 Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Hung Hom Kowloon Hong Kong Peoples R China Cent South Univ Sch Geosci & Infophys Changsha 410083 Peoples R China

Water current continuously provides driving force and kinetic energy to vessels under downstream conditions. However, research has yet to elucidate the impact of the water-flow effect during vessel-bridge collisions, particularly in vessel collisions due to anchor dragging. Hence, physics-based finite-element (FE) models considering fluid-structure interactions are developed. The developed models accurately replicate the waterdriven barge collision accident of the Taiyangbu Bridge, demonstrating the rationality of the modeling method. It is found that the water-flow effect extends the duration of vessel-bridge collisions and increases the pier displacement, indicating the non-conservatism of neglecting the water-flow effect in current studies. Moreover, this study proposes a simplified analysis method considering the water-flow effect as an alternative approach to the explicit fluid-structure interaction simulation. In the proposed method, the user-defined load subroutine, LOADUD, is employed to simulate the driving force of water current and achieves the equivalent of the water-flow effect through the water force-velocity relationship curve. The simplified method is demonstrated to have acceptable accuracy and efficiency compared with the fluid-structure interaction simulation. Considering the trade-off between computational efficiency and accuracy, the simplified method is more suitable for estimating the structural dynamic response of bridges subjected to vessel collisions with the water-flow effect.

关键词： Vessel-bridge collision Side impact Water-flow effect fluid-structure interaction User-defined load subroutine

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Finite element model to investigate the dynamic instability of ring stiffened conical shells subjected to flowing fluid

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FINITE ELEMENTS IN ANALYSIS AND DESIGN 2024年 241卷

作者： Esmaeilzadehazimi, Mohammadamin Lakis, Aouni A. Toorani, Mohammad Ecole Polytech Montreal Mech Engn Dept CP 6079 Montreal PQ H3C 3A7 Canada

In this study, the vibration stability (i.e., static divergence) and critical velocity of fluid- conveying, ring-stiffened, truncated conical shells are investigated under various boundary conditions. The shell is characterized using Sanders' theory, while the fluid is modeled using a velocity potential approach with the impermeability condition at the fluid-shell interface. Using linear superposition, the natural frequencies corresponding to each flow velocity are determined by satisfying the dynamic characteristic equation and boundary conditions. Critical velocities are identified where the natural frequencies vanish, indicating static divergence. Parametric studies are conducted to investigate the effect of ring stiffeners on the critical velocities with respect to the semi-cone angle, number of rings, and boundary conditions. The proposed model is validated through comparison with published data. It is found that the rings significantly affect the stability of the cone under different boundary conditions. Instability in stiffened shells occurs at higher critical fluid velocities than in unstiffened shells across all boundary conditions. An increase in the vertex angle leads to a decrease in critical flow discharge.

关键词： Finite element method fluid-structure interaction Conical shell Static divergence Ring stiffeners

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Free vibrational behavior of functionally graded carbon nanotube composite fluid-filled cylindrical-conical shell: Analytical and experimental investigation

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MECHANICS BASED DESIGN OF structureS AND MACHINES 2024年第2期52卷 1014-1041页

作者： Babaei, Mohammad Javad Jafari, Ali Asghar Ramezani, Farin KN Toosi Univ Technol Dept Mech Engn Tehran Iran Univ Porto Dept Mech Engn Fac Engn Porto Portugal

This investigation analyzes the effects of internal static fluid on the free vibrational behavior of joined shells made of carbon nanotube (CNT) fiber-reinforced composite. Various types of functionally graded CNTs composite with temperature dependence are considered. Classic shell theory and Love's assumptions combined with Hamilton's principle are used to obtain motion equations. Bernoulli equation, velocity potential, and impermeability condition are employed to the coupling effects of fluid pressure with motion equations of shells. Continuity conditions in the joint point of conical and cylindrical sections are supposed to couple equations of two parts. The generalized differential quadrature (GDQ) method is employed to solve equations for various boundary conditions. Experimental modal tests on a sample made by the 3-D printer and prior others' research are used to validate the accuracy of results. Consequently, parametric studies are expressed, such as longitudinal and circumferential mode numbers, semi-vertex angle, distributions of CNTs, CNTs fraction volumes, fluid density, shell thickness, and operating temperature. According to the results, although fluid decreases the frequency generally, the process of changing frequency in terms of other parameters is similar.

关键词： Joined shell conical-cylindrical shell vibration modal testing fluid-structure interaction

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