In this paper, we will present an approach to compute the signed distance or level set function from the Standard Triangle Language (STL) file format. Then the level set is used to represent the surface of a given obj...
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ISBN:
(纸本)9789811671609;9789811671593
In this paper, we will present an approach to compute the signed distance or level set function from the Standard Triangle Language (STL) file format. Then the level set is used to represent the surface of a given object inside the computational domain. The continuity and Navier-Stokes equations are solved numerically to study the fluid flows over the solid body. The finite-volume method (FVM) is applied to approximate all terms in the governing equations to conserve mass and momentum. The cut-cell method is employed to avoid recomputing the mesh points when the body moves around. The transport equation for the level set function is solved accordingly to update the position of the object.
In this work we implement the parallelization of a method for solving fluid-structure interactions: one-field monolithic fictitious domain (MFD). In this algorithm the velocity field for solid domain is interpolated i...
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ISBN:
(纸本)9783031087608;9783031087592
In this work we implement the parallelization of a method for solving fluid-structure interactions: one-field monolithic fictitious domain (MFD). In this algorithm the velocity field for solid domain is interpolated into fluid velocity field through an appropriate L-2 projection, then the resulting combined equations are solved simultaneously (rather than sequentially). We parallelize the finite element discretization of spatial variables for fluid governing equations and linear system solver to accelerate the computation. Our goal is to reduce the simulation time for high resolution fluid-structure interaction simulation, such as collision of multiple immersed solids in fluid.
During the last 20 years, fluid-related natural catastrophes caused by climate change have produced severe floods in numerous countries, resulting in many casualties, large scale infrastructure damage, and enormous ec...
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During the last 20 years, fluid-related natural catastrophes caused by climate change have produced severe floods in numerous countries, resulting in many casualties, large scale infrastructure damage, and enormous economic losses. These catastrophic hydrodynamic phenomena disrupt whole transportation networks by washing down bridge decks, piers, and roadways, complicating rescue and recovery efforts. As recent flash floods have demonstrated, inland transportation infrastructure is just as vulnerable to fluid hazards as coastal infrastructure. This research investigates the mechanics of fluid flow impact to learn how fluid currents affect bridge piers. The next step is to build a finite volume bridge pier model that considers the consequences of fluid flow and radial motion around the pier. Results from fluid impact analysis, fluid-structure coupling analysis, and theoretical analysis are contrasted with those derived using the equations specified by national and international design standards. According to the results, it is necessary to raise the fluid flow force computed using the codes' formulas to account for the impact of the flood on the bridge pier. The standard codes for the highway bridge design approach frequently produce a larger fluid flow force result, so we can ignore fluid-structure interaction on the bridge pier in water flow velocity, which is minor. It is possible to disregard the fluid-structure interaction on the bridge pier only when finite volume analysis is performed. Understanding the impact of fluid flow on bridge piers is crucial for enhancing the resilience of transportation infrastructure in the face of increasing hydrodynamic threats due to climate change. This research delves into the mechanics of fluid-structure interaction, shedding light on how fluid currents affect bridge stability. By developing a finite volume bridge pier model, the study provides a more accurate assessment of the forces exerted by floods, enabling engineers to d
A Computational fluid Dynamics (CFD) analysis of air entrapment and structural response during flat plate entry to water is presented. Slamming loads remain of concern for the design of safe and efficient ships and of...
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ISBN:
(纸本)9780791885925
A Computational fluid Dynamics (CFD) analysis of air entrapment and structural response during flat plate entry to water is presented. Slamming loads remain of concern for the design of safe and efficient ships and offshore structures to ensure structural integrity during extreme. Besides ships with large bow flare or horizontal stern planes, slamming events also occur for fast small craft with stepped hulls. Ditching of airplanes and vehicle wading represent non-marine applications. The advance of computational methods in engineering has enabled fluid-structure interaction (FSI) simulations for slamming. A crucial task of solving the coupled fluid and structural problem is the accurate resolution of free surface dynamics and phase interactions between water and air. Numerical ventilation on the bottom plating can arise due to discretization issues and curtail the resolution of physical aeration effects. The study at hand was based on a Finite-Volume (FV) method and the numerical solution of Reynolds-averaged Navier-Stokes (RANS) equations. Emphasis was laid on numerical techniques to contain numerical ventilation whilst limiting the increase in computational cost. In doing so, adaptive discretization schemes were employed. Namely, model-based adaptive mesh refinement (AMR) and time stepping for both motions of bodies (rigid and elastic) and the free surface. Additionally, the underlying Volume of fluid (VoF) method was enhanced through consideration of slip between water and air to improve air entrapment predictions. Comparison was drawn to a novel experimental analysis for which both structural responses and high-resolution imagery of aeration were available. It was demonstrated that above enhancements not only lead to better capturing of air entrapment and reduced numerical ventilation, but also offered more flexible modeling concepts and potential performance gains.
This paper builds upon a two-degree-of-freedom Van der Pol oscillator based Reduced-Order Model for studying the mechanisms around Non-Synchronous Vibrations (NSV) in turbomachinery. One degree tracks the fluid motion...
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ISBN:
(纸本)9780791886120
This paper builds upon a two-degree-of-freedom Van der Pol oscillator based Reduced-Order Model for studying the mechanisms around Non-Synchronous Vibrations (NSV) in turbomachinery. One degree tracks the fluid motion utilizing a combination of a traditional Van der Pol Oscillator and a Duffing Oscillator;the other degree of freedom is a mass on a spring and a damper, in this case a cylinder. Thus, this model can be considered one of fluid-structure interaction. The cubic stiffening from the Duffing Oscillator proved to improve the match to experimental data. Using this model to study the time-history of the fluid and the structure oscillation, additional parameters are extracted to understand the underlying mechanisms of frequency lock-in and limit cycle oscillation. First, the phase shift between the vortex shedding and the structural motion is calculated when it locks-in then unlocks. Second, the work done per cycle is analyzed from the contributions of the mass, spring, and damping forces to determine the dominant contributor when locking-in versus unlocking. Third, the phase portrait is plotted on a Poincare Map to further study the locked-in versus unlocked responses. This model is then validated against not only experimental data, but also computational simulation results and previous reduced-order models. The finalized model can now serve as a preliminary design tool for turbomachinery applications. For more realistic and accurate modeling, a third degree-of-freedom in the form of an airfoil pitching motion will be added in a separate paper as well.
During the operation of a turbine, the water level drop can cause vibration and damage to the flow components, severely threatening its stability and reliability. Investigating the impact of operational parameters on ...
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During the operation of a turbine, the water level drop can cause vibration and damage to the flow components, severely threatening its stability and reliability. Investigating the impact of operational parameters on the internal flow field and flow structures of tidal turbines under low flow conditions is crucial for peak shaving and deployment of tidal power stations. This paper takes a 24MW turbine as the research object, using numerical calculations to analyze the effects of tailwater height on the flow characteristics and structural properties of the unit under low flow conditions. It studies the hydraulic impact on the flow component walls under different operating parameters and verifies the reliability of numerical calculations through vibration and stress tests. The results show that the increase in tailwater level affects the turbine's flow characteristics, forming large-scale, high-intensity vortices in the internal flow field and causing pressure pulsations near the wall surface. Modal analysis reveals that under different tailwater heights, the maximum modal effective mass exists along the axis of the impeller, with modal frequencies higher than the main frequencies of pressure pulsations. The impeller region corresponds to the turbine chamber wall bearing significant stress, which induces strain. The magnitude of stress and the degree of strain are positively correlated with the tailwater height. The research findings provide guidance for tailwater regulation and stable operation of tidal power stations.
The term "viscoelastic pipe" refers to high polymer pipes that exhibit both elastic and viscoelastic properties. Owing to their widespread use in water transport systems, it is important to understand the tr...
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The term "viscoelastic pipe" refers to high polymer pipes that exhibit both elastic and viscoelastic properties. Owing to their widespread use in water transport systems, it is important to understand the transient flow characteristics of these materials for pipeline safety. Despite extensive research, these characteristics have not been sufficiently explored. This study evaluates the impact of friction models on the transient flow of viscoelastic pipes across various Reynolds numbers by employing an energy analysis approach. Given the complexity and computational demands of two-dimensional models, this paper compares the accuracy of one-dimensional and quasi-two-dimensional models. Notably, the superiority of the quasi-two-dimensional model in simulating viscoelastic pipelines is demonstrated. Owing to the interaction between pressure waves and fluid within viscoelastic pipes, fluid-structure coupling significantly attenuates pressure waves during transmission. These findings shed light on the constitutive properties of viscoelastic pipes and the influence of pipe wall friction models on transient hydraulic characteristics, building upon prior studies focused on elastic pipes. Nevertheless, numerous factors affecting transient flow in viscoelastic pipes remain unexplored. This paper suggests further analysis of strain effects, starting with temperature and pipe dynamics, to enhance the understanding of the coupling laws and flow mechanisms in viscoelastic pipelines.
Background and Objective: In the current work, we present a descriptive fluid-structure interaction computational study of the end -to -side radio-cephalic arteriovenous fistula. This allows us to account for the diff...
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Background and Objective: In the current work, we present a descriptive fluid-structure interaction computational study of the end -to -side radio-cephalic arteriovenous fistula. This allows us to account for the different thicknesses and elastic properties of the radial artery and cephalic vein. Methods: The core of the work consists in simulating different arteriovenous fistula configurations obtained by virtually varying the anastomosis angle, i.e. the angle between the end of the cephalic vein and the side of the radial artery. Since the aim of the work is to understand the blood dynamics in the very first days after the surgical intervention, the radial artery is considered stiffer and thicker than the cephalic vein. Results: Our results demonstrate that both the diameter of the cephalic vein and the anastomosis angle play a crucial role to obtain a blood dynamics without re-circulation regions that could prevent fistula failure. Conclusions: When an anastomosis angle close to the perpendicular direction with respect to the radial artery is combined with a large diameter of the cephalic vein, the recirculation regions and the low Wall Shear Stress (WSS) zones are reduced. Conversely, from a structural point of view, a low anastomosis angle with a large diameter of the cephalic vein reduces the mechanical stress acting on the vessel walls.
Considering the fluid-structure impacting failure problems with large size, this paper presents an extended multiresolution smoothed particle hydrodynamics (SPH)-peridynamics (PD) coupling model. The influence domain ...
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Considering the fluid-structure impacting failure problems with large size, this paper presents an extended multiresolution smoothed particle hydrodynamics (SPH)-peridynamics (PD) coupling model. The influence domain and the interpolation smoothing length are innovatively introduced to reconstruct governing equations for interactions between particles of diverse resolutions, ensuring system-wide momentum conservation. Then, an adaptive multi-level cell neighborhood search (AMC-NS) algorithm is presented, designed to reduce the time of neighborhood search in multi-resolution simulations. Several 2D and 3D validation tests demonstrate the accuracy of the multi-resolution SPH-PD model in describing solid deformation and fluid impact pressure. The multi-resolution SPH-PD model significantly enhances computational efficiency and can depict the process of structural failure under conditions where a wide difference in scale between waves and structures.
This paper investigates the dynamic stability of laminated cylindrical shell submerged in a fluid. Assuming that the fluid is incompressible satisfying the Laplace equation, the coupling relationship between the exter...
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This paper investigates the dynamic stability of laminated cylindrical shell submerged in a fluid. Assuming that the fluid is incompressible satisfying the Laplace equation, the coupling relationship between the external pressure from fluid acting on the cylindrical shell and the velocity potential function of the fluid is deduced by using Bernoulli law. Based on Karman-Donnell's thin shell theory, the governing equations for dynamic buckling of the composite laminated cylinder are established by introducing the constitutive relationship for laminated composite structures. Likely functions of the displacement and the stress function for cylindrical shell are proposed to construct Mathieu-Hill equation for dynamic stability of laminated cylindrical shell with fluid-structure interaction and the first three order dynamic instability regions are derived. A good agreement between the solutions from the proposed analysis and from the available literatures justified the accuracy and validity of the proposed analysis. With the established analysis, the influence of various parameters on the dynamic stability of cylinders are analyzed, from which a dynamic stability enhancement scheme suitable for composite laminated cylinders is summarized. It is found that the fluid-structure interaction will greatly reduce the excitation frequency of laminated cylindrical shells but has no effect on their vibration modes.
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