Fluid-structure Interaction Phenomena Research Articles

Numerical FSI investigation based on LES: Flow past a cylinder with a flexible splitter plate involving large deformations (FSI-PfS-2a)

The objective of this paper is to provide a detailed numerical investigation on the fluid–structure interaction (FSI) test case presented in Kalmbach and Breuer (J. of Fluids and Structures, 42, (2013), 369–387). It relies on detailed experimental investigations on the fluid flow and the structure deformation using modern optical measurement techniques such as particle-image velocimetry and laser triangulation sensors. The present numerical study is based on an efficient partitioned FSI coupling scheme especially developed for turbulent flow simulations around light-weight structures using large-eddy simulation. The current FSI configuration is composed of a fixed cylinder with a flexible thin rubber plate and a rear mass inducing a turbulent flow (Re=30,470). Mainly based on a movement-induced excitation the flexible structure oscillates in the second swiveling mode involving large deformations. Thus, particular attention has been paid to the computational model and the numerical set-up. Special seven-parameters shell elements are applied to precisely model the flexible structure. Structural tests are carried out to approximate the optimal structural parameters. A fine and smooth fluid mesh has been generated in order to correctly predict the wide range of different flow structures presents near and behind the flexible rubber plate. A phase-averaging is applied to the numerical results obtained, so that they can be compared with the phase-averaged experimental data. Both are found to be in close agreement exhibiting a structure deformation in the second swiveling mode with similar frequencies and amplitudes. Finally, a sensitivity study is carried out to show the influence of different physical parameters (e.g. Young’s modulus) and modeling aspects (e.g.subgrid-scale model) on the FSI phenomenon.

Experimental evaluation of the air trapped during the water entry of flexible structures

Deformable structures entering the water might experience several fluid-structure interaction (FSI) phenomena; air trapping is one of these. According to its definition, it consists of air bubbles trapped between the structure and the fluid during the initial stage of the impact. These bubbles might reduce the peak impact force. This phenomenon is characteristic for the water entry of flat-bottom structures. Above a deadrise angle of 10°, air trapping is negligible. In this work, we propose a methodology to evaluate the amount of air trapped in the fluid during the water entry. Experiments are performed on wedges with varying stiffness, entry velocity, and deadrise angle. A digital image post- processing technique is developed and utilized to track the air trapping mechanism and its evolution in time. Interesting results are found on the effect of the impact velocity and the structural deformation on the amount of air trapped during the slamming event.

Experimental investigation of the fluid–structure interaction in an elastic 180° curved vessel at laminar oscillating flow

Fluid–structure interaction phenomena are extremely important when laminar flows through elastic vessels such as in biomedical flow problems are considered. In general, such elastic vessels are curved which is why an elastic 180° bend at a curvature ratio $$\delta = D/D_{\rm C} = 0.\bar{2}$$ defines the reference geometry in this study. It is the purpose of this study to compare the results with the steady flow through a 180° rigid pipe bend and to quantify the impact of the fluid–structure interaction on the overall flow pattern and the vessel deformation at oscillating fully developed entrance flow. The findings comprise velocity, pressure, and structure deformation measurements. The vessel dilatation amplitude was varied between 3.75 % and 7 % of the vessel diameter at Dean De and Womersley number Wo ranges of $$327\,\le\,De\,\le\,350$$ and $$7\,\le\,Wo\,\le\,8.$$ The flow is investigated by time-resolved stereoscopic particle-image velocimetry in five radial cross sections located in the elastic 180° bend and in the inlet pipes. The unsteady static vessel pressure is measured synchronously at these cross sections. The comparison of the steady with the unsteady flow field shows a strong change in the axial and secondary velocity distributions at periods of transition between the centrifugal forces and the unsteady inertia forces dominated regimes. These changes are characterized by asymmetric fluctuations of the centers of the counter-rotating vortex pair. The investigation of the impact of the structure deformation amplitude on these fluctuations reveals a significant attenuation at high deformation amplitudes. The spatial motion of the elastic vessel due to the forces applied by the flow exhibits amplitudes up to 15 % of the vessel diameter. Considering the fluid–structure interaction, an amplification of the volume flux amplitude by a factor of 2.1 at the vessel outlet and phase lags up to 30° occur. The static pressure distribution is characterized by a pronounced asymmetry between forward and backward flow with a 40 % higher peak magnitude at backward flow and phase lags of 35°. The results evidence that a strong distortion of the velocity distribution in the bend, which is caused by the oscillating nature of the flow, is reduced as a result of the fluid–structure interaction.

Experimental and numerical studies of fluid–structure interaction phenomena inside the head when subjected to a dynamical loading

Brain injury constitutes one of the major causes of death in road accidents. Finite element (FE) models are commonly used to investigate the biomechanics of head impact since they enable an enhance...

Finite Element Analysis of Deep Elliptical Submersible Pressure Hull Subjected to a Side-On Non-Contact Underwater Explosion

Predicting the dynamic response of a floating and submerged structure subjected to underwater explosion is greatly complicated by the explosion of a high explosive, propagation of shock wave, bubble-pulse, complex fluid-structure interaction phenomena and the dynamic behavior of the floating structures. A numerical simulation has been carried out to examine the behavior of elliptical submersible pressure hull to non-contact underwater explosion (UNDEX) and take the effect of bubble-pulse. The finite element package ABAQUS was used to model the UNDEX and the fluid-structure interaction (FSI) phenomena. The pressure wave resulting from an UNDEX was assumed to be a spherical wave. Plastic strain and the time histories of the wet-surface displacement, velocity and von Mises stress are presented. The analytical results are valuable for designing underwater vehicles to resist UNDEX.

Physical and numerical large-scale wave basin modeling of fluid-structure interaction and wave impact phenomena

Physical and numerical large-scale wave basin (LSWB) modeling of fluid-structure interaction (FSI) and wave impact phenomena are examined in this study. In particular, the role of numerical modeling and simulation in designand analysis of physical LSWB FSI andwave impact experiments using a numerical wave basin (NWB) modeling approach is examined. Physical characteristics and testing capabilities of arepresentative LSWBare first described. Selectedphysical FSI and wave impactexperiments pertaining to civil, energy and naval engineering disciplines conducted at the LSWB and the accompanying NWBFSI modeling and simulations of these challenging phenomenaare presented. An effort to further improvetheNWBFSI softwarewith highly nonlinear wave impact modeling capabilities to facilitate physical FSI experiment design and testing,and details of an on-goingNWBdevelopment and validation processesare delineated.It is demonstrated that the NWBFSI software is useful in facilitating the design of complex, highly nonlinear FSI and wave impactexperiments. Conversely, the resulting measured data from the FSI and wave impact experiments can be used to validate and identify further modeling improvement needs of the NWBFSI and wave impactsoftware.

Investigation of Wake Effects on Aeroelastic Responses of Horizontal-Axis Wind-Turbines

Wake effects of a horizontal-axis wind-turbine blade on aeroelastic characteristics were investigated under normal operational conditions. A structural analysis was performed employing a nonlinear beam model based on the large deflection beam theory. For inflow analysis on rotor blades, a free-vortex wake method was employed. An advantage of the present approach is its ability to calculate directly the induced velocities from the wake. Also, for the predictions of aerodynamic loads, a fully turbulent flow solution is invoked in FLUENT, where the SST turbulent model of two-dimensional airfoils is adopted for transient analysis. To verify and validate the aerodynamic model for wind turbines, the wake geometry and the aerodynamic coefficients from the present simulation are compared with measurements and numerical results of previous studies. Finally, an analysis of the tightly coupled fluid–structure interaction phenomena of a wind-turbine blade has been carried out to investigate aeroelastic characteristics, such as steady-state blade deflections and dynamic stability. The present results are compared with the numerical results obtained using a uniform inflow model, which clearly confirms the importance of wake effects on the blade aeroelastic characteristics.

A parallel iterative partitioned coupling analysis system for large-scale acoustic fluid–structure interactions

In many engineering fields, dynamic response in fluid---structure interaction (FSI) is important, and some of the FSI phenomena are treated as acoustic FSI (AFSI) problems. Dynamic interactions between fluids and structures may change dynamic characteristics of the structure and its response to external excitation parameters such as seismic loading. This paper describes a parallel coupling analysis system for large-scale AFSI problems using iterative partitioned coupling techniques. We employ an open source parallel finite element analysis system called ADVENTURE, which adopts an efficient preconditioned iterative linear algebraic solver. In addition, we have recently developed a parallel coupling tool called ADVENTURE_Coupler to efficiently handle interface variables in various parallel computing environments. We also employ the Broyden method for updating interface variables to attain robust and fast convergence of fixed-point iterations. This paper describes key features of the coupling analysis system developed, and we perform tests to validate its performance for several AFSI problems. The system runs efficiently in a parallel environment, and it is capable of analyzing three-dimensional-complex-shaped structures with more than 20 million degrees-of-freedom (DOFs). Its numerical results also show good agreement with experimental results.

A finite volume study for pressure waves propagation in a straight section of pipeline with caviation

The main objective of this research was to study the pressure waves propagation generated by a sudden closure of a valve in a straight pipe. The physical model consisted of a head tank that can be pressurized with air, and a copper pipe with a fast-closing ball valve on the downstream end of the line. The cavitation and fluid-structure interaction phenomena were integrated analytically into the one-dimensional continuity and momentum equations, by assuming that the fluid density and the flow area vary with pressure. These equations were solved through a high resolution finite volume method, in combination with others numerical methods such as Taylor series expansion, Newton method, Simpson's Rule and quadratic interpolation. Due to the complexity of the solution procedure, a computational code in FORTRAN 95 language was developed in order to obtain numerical solutions. Several discretizations of the computational grid were achieved to assess their impact on the solution. The model was validated with experimental data and analytic results obtained by other researchers. Several pressure values, in different points of pipe, were compared, and an excellent agreement was found for both cases.

Full Eulerian finite element method of a phase field model for fluid–structure interaction problem

In this paper we present a full Eulerian model for a dynamic fluid–structure interaction (FSI) problem in terms of phase field approach, and design its full Eulerian finite element discretization and effective iterative method. The present full Eulerian FSI model effectively demonstrates the interaction between fluid flow and solid structure in terms of a uniform system of governing equations defined in a single domain, thus the computational grid is fixed, and the re-meshing and interpolation techniques which are always required by other FSI modeling approaches are no longer needed here. We develop a new stable scheme to discretize the Euler equation of an incompressible hyperelastic structure in Eulerian description, and employ Galerkin/least-square (GLS) stabilization scheme, streamline-upwind/Petrov–Galerkin (SUPG) method, and the second-order backward difference formula (BDF) to solve the derived transient nonlinear system of Navier–Stokes equations and transport equations. Numerical experiment is carried out for a cross spinning around its rotation of axis due to the passing flow field, and the numerical results dramatically show the spinning motion of the cross due to the interaction with the fluid, showing that our model and numerical methods are effective to simulate the dynamic fluid–structure interaction phenomena.

Experiment Verification and Model Analysis of Partially-Filled Liquid Tank under Different Liquid Level

In order to analyze the vibration performance of partially-filled liquid tank of ships, this paper takes the integration of measures including numerical simulation with finite element method and experimental verification with LMS vibration test and model analysis system of steel liquid tank under different liquid level conditions to study the fluid-structure interaction phenomenon. With the software of ADINA, the FEM model of the tank is developed and the model analysis which indicates the vibration modes and natural frequencies is completed. The simulation is compared with the experimental results which shows the natural frequency of the structure decreases with the level increases.

Fluid–structure interaction analysis on the effect of chip stacking in a 3D integrated circuit package with through-silicon vias during plastic encapsulation

This paper presents the effect of chip stacking in a 3D integrated circuit package during plastic encapsulation. An experiment was conducted on four stacked chips with bumps in a perimeter array. The flow front advancement and chip displacement in the experiment were validated by using FLUENT 6.3 and ABAQUS 6.9, respectively. A total of four models, which consist of two, three, four, and five stacked chips with through-silicon vias, were studied numerically. A simultaneous or direct solution procedure was employed to solve the variables of the fluid/structural domain. This approach provides better visualization of the actual plastic encapsulation process by considering the fluid–structure interaction phenomenon during the process. A constant ratio of inlet and outlet gate heights was applied to create a more uniform flow front advancement among the models. Results indicate that the highest displacement occurred in Model 4, which contains the most stacked chips. The highest von Mises stress was also detected in Model 4. Therefore, unfavorable deformation is anticipated when more stacked chips are employed. The experimental and numerical studies provide useful information in understanding the fluid flow of epoxy resin and subsequent structural deformation under the effect of chip stacking.

Study on the fluid‐structure interaction of flexible printed circuit board motherboard in personal computer casings

PurposeThe flexible printed circuit board (FPCB) can be an alternative to the rigid printed circuit board because of its excellent flexibility, twistability, and light weight. Using FPCB to construct personal computer (PC) motherboard is still rare. Therefore, the present study aims to investigate the fluid‐structure interaction (FSI) behaviors of the newly proposed FPCB motherboard under fan‐flow condition in the PC casings.Design/methodology/approachThe deflection and stress induced, which are usually ignored in the traditional rigid motherboard, are the main concern in the current FPCB motherboard studies. Only a few studies have been conducted on the effect of inlet locations, effect of inlet sizes, effect of multi‐inlets, and effect of a two‐fan system. These numerical analyses are performed using the fluid flow solver FLUENT and the structural solver ABAQUS; they are real‐time online coupled by Mesh‐based Parallel Code Coupling Interface (MpCCI).FindingsA smaller inlet size can cause higher deflection and stress fluctuations, but the fluctuations can be reduced by incorporating the multi‐inlets design. In addition, the inlet locations and two‐fan system can prominently affect the magnitudes of the deflection and stress induced.Practical implicationsThe current study provides better understanding and allows designers to be aware of the FSI phenomenon when dealing with the FPCB motherboard. Although the present study primarily focuses on the motherboard, the findings could also contribute valuable information for other FPCB applications.Originality/valueThe present study extends the FSI investigation from the previous novel approach of FPCB motherboard, and uniquely explores the behaviors of the FPCB motherboard inside different PC casings.

Dynamic Response of Stiffened Plates Subjected to Underwater Shock Loading

The dynamic response of a floating structure subjected to underwater explosion is greatly complicated by the explosion of a high explosive, propagation of shock wave, complex fluid–structure interaction phenomena, and the dynamic behavior of the floating structures. A numerical investigation has been carried out to examine the behavior of stiffened steel plates subjected to shock loads resulting from an Underwater Explosion (UNDEX). The aim of this study is to enhance the dynamic response of stiffened plates to resist underwater shock loading. A non-linear dynamic numerical analysis of the underwater explosion phenomena associated with different geometrical stiffened steel plates is performed using theABAQUS/Explicit finite element program which provides an important analysis tool that can help engineers and designers to design and construct better structures to resist shock loads. Special emphasis is focused on the evolution of mid-point displacements and the maximum displacements. Further investigations have been performed to study the effects of including material damping and the rate-dependent material properties. The results obtained show that the inclusion of a damping material can absorb energy under blast load. It helps to reduce the force transmitted to the main structure. The inclusion of damping material helps to reduce the displacement of the plates. The results indicate that stiffener configurations affect greatly the overall performance of tested steel plates. The displacement–time histories are presentedwhich will be used in designing stiffened panels so as to enhance resistance to under water shock damage. The obtained numerical results can help in proposing design guidelines for floating structures in order to enhance the resistance to underwater shock damage, since explosive tests are considered costly and dangerous.

단순형태 세일의 변형에 대한 유체-구조 연성 해석

Since most of yacht sails are made of thin fabric, they form cambered sail shape that can efficiently generate lift power by aerodynamic interaction and by external force delivered from supporting structures such as mast and boom. When the incident flow and external force alter in terms of volume or condition, the shape of sail also change. This deformation in shape has impact on the peripheral flow and aerodynamic interaction of the sail, and thus it is related to the deformation of the sail in shape again. Therefore, the precise optimization of aerodynamic performance of sail requires fluid-structure interaction (FSI) analysis. In this study, the simplified sail without camber was under experiment for one-way FSI that uses the result of flow analysis to the structural analysis as load condition in an attempt to fluid-structure interaction phenomenon. To confirm the validity of the analytical methods and the reliability of numerical computation, the difference in deformation by the number of finite element was compared. This study reproduced the boundary conditions that sail could have by rigs such as mast and boom and looked into the deformation of sail. Sail has non-linear deformation such as wrinkles because it is made of a thin fabric material. Thus non-linear structural analysis was conducted and the results were compared with those of analysis on elastic material.

Influence of irregular canyon shape on location of truncation surface

Abstract Fluid–structure interaction phenomenon, by its nature, is three-dimensional and consequently dependant on the shape of a dam and canyon that in-fact defines the spatial domain where the generated acoustic waves are spread. The complex topography of the terrain in general requires sufficiently large extent of reservoir to be included in the model, which is undoubtedly feasible if BEM technique is used. This paper shows that the irregular canyon shape dictates “the most adequate” location of the truncation surface that gives the smallest negative impact on calculation accuracy. The derived conclusions are based on various 3D analyses of a rigid dam–reservoir system with different shapes and lengths of the fluid domain, where the fluid is treated as incompressible and inviscid. The presented work contributes towards disclosure of the topographic site effects and towards promotion of simple and effective procedure for generation of BE mesh, which is quite accurate in following the topology of the terrain.

Computational analysis of fluid–structure interaction based blast-mitigation effects

Advanced non-linear dynamics, finite element computational methods and tools are utilized in order to assess the blast wave mitigation potential of the fluid–structure interaction phenomena involving rigid and deformable structures. The employed computational methods and tools are verified and validated by first demonstrating that they can quite accurately reproduce analytical solutions for a couple of well-defined blast wave propagation and interaction problems. Then the methods/tools are used to investigate the fluid–structure interaction phenomena involving deformable structures while accounting for both the interaction of the incident blast wave with the structure and for the structure-motion induced blast wave (at the back-face of the structure). To assess the role of the structure deformability, i.e. the role of the shock waves generated within the structure, the results obtained are compared with their rigid structure counterparts. This comparison established that no additional structure-deformability-related blast-mitigation effects are observed in the case of fully supported blast wave loading while, under exponentially decaying blast wave loading, such effects are observed but only under conditions when the shock wave propagation time within the structure is comparable with the incident wave decay time.

FSI implications of EMC rheological properties to 3D IC with TSV structures during plastic encapsulation process

In this paper, an efficient numerical approach has been adopted to analyze the fluid/structure interaction (FSI) implications to 3D IC with through-silicon via (TSV) structures during plastic encapsulation process, under the effect of different EMC rheological properties. A simultaneous or direct solution procedure is employed to solve the solution variables of fluid/structural domain together. Therefore, this approach can provide better visualization of the actual plastic encapsulation process by considering FSI phenomenon during the process. Different epoxy molding compound (EMC) rheological properties have resulted dissimilar fluid flow characteristics, pressure distribution, air void entrapment level, structural displacement and von Mises stress, which are discussed in the paper. Unfavorable results are obtained when higher viscous flow takes place. EMC flow front prediction has been validated with the experimental results from literature. The numerical approach and results presented in this paper are able to provide useful information for the works in optimizing plastic encapsulation process.

Water entry of flexible wedges: Some issues on the FSI phenomena

Deformable bodies entering the water can face unexpected fluid–structure interaction (FSI) phenomena introduced by the mutual interaction between the fluid motion and the structural deformations. This brief communication presents some preliminary results on the FSI phenomena involved with the water entry of deformable wedges. Wedges with various deadrise angle and flexibility impact the water at different velocities. Two different kinds of FSI are found: (i) a repetition of impacts and separations in the fluid jet and (ii) a tendency to cavitation in the underwater fluid–structure interface. These experimental findings are important since large deformations are found to introduce clearly visible FSI phenomena commonly neglected or ignored, but crucial to correctly predict the hydrodynamic load.

Fluid/Structure Interaction Investigation in PBGA Packaging

This paper presents experimental and simulation studies of 3-D fluid/structure interaction (FSI) of wire sweep during the encapsulation process of plastic ball grid array (PBGA) packaging in different dies (single and stacked dies). A scaled-up package is fabricated to emulate the encapsulation of PBGA packaging and to study the effects of the FSI phenomenon in the PBGA package. A 3-D model of the mold and wires is created using GAMBIT, and the FSI is simulated using FLUENT and ABAQUS software integrated with mesh-based parallel code coupling interface for the real-time calculations. The effects of the stacked die and inlet pressure of the mold cavity on the melt flow behavior and wire sweep are mainly studied. A constant viscosity of the test fluid is assumed for the experiment. The volume-of-fluid technique is applied for melt-front tracking in the analysis. The numerical results of melt-front patterns and wire sweep are compared with the experimental results and good conformity is found. It is observed that the stacked die significantly influences the melt-front profile and the eventual wire sweep; as the number of dies in the stack increases, the wire sweep also increases.