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The aerodynamic performance of a moving flapping wing is investigated numerically using a fluid–solid interaction model. The flow field is assumed to be two-dimensional, viscous, unsteady, and incompressible. Galerkin-least/squares finite element method is used to account for the convective nature of the flow field. The flow solver is coupled with the rigid body equations of motion describing the movement of the flapping wing. An interface-capturing technique is developed and tailored to the present model to capture the flapping wing during its movement. The developed algorithm is validated against published data with a great degree of success. Then, simulations for a flapping wing with a stationary center of gravity and free center of gravity motion, are performed. This is followed by a parametric study through which the effects of the wing’s initial position, maximum flapping angle, Reynolds number, the mass of the wing, the gravitational acceleration, and the critical frequency for each Reynolds number are studied. Finally, the voluntary vertical takeoff of a fruit fly, Drosophila Melanogaster is simulated using the proposed model. [ABSTRACT FROM AUTHOR]

A finite element method is employed to examine the impact of a magnetic field on the development of plaque in an artery with stenotic bifurcation. Consistent with existing literature, blood flow is characterized as a Newtonian fluid that is stable, incompressible, biomagnetic, and laminar. Additionally, it is assumed that the arterial wall is linearly elastic throughout. The hemodynamic flow within a bifurcated artery, influenced by an asymmetric magnetic field, is described using the arbitrary Lagrangian–Eulerian (ALE) method. This technique incorporates the fluid–structure interaction coupling. The nonlinear system of partial differential equations is discretized using a stable P2P1 finite element pair. To solve the resulting nonlinear algebraic equation system, the Newton-Raphson method is employed. Magnetic fields are numerically modeled, and the resulting displacement, velocity magnitude, pressure, and wall shear stresses are analyzed across a range of Reynolds numbers (Re = 500, 1000, 1500, and 2000). The numerical analysis reveals that the presence of a magnetic field significantly impacts both the displacement magnitude and the flow velocity. In fact, introducing a magnetic field leads to reduced flow separation, an expanded recirculation area near the stenosis, as well as an increase in wall shear stress. [ABSTRACT FROM AUTHOR]

This paper investigates the hydrodynamics of a bent elastic tube with an instantaneously deformed wall using an arbitrary Lagrangian-Eulerian (ALE) finite element method. The study reveals that the tube deforms continuously with the fluid's progression, exhibiting diverse deformation patterns. The flow patterns do not adhere to Poiseuille's profile, with higher velocities detected on the inner side of the bent region during deformation. The results deepen insights into hydrodynamics within bent elastic tubes and bring significance for the design of curved pipelines. [ABSTRACT FROM AUTHOR]

A finite element method is employed to examine the impact of a magnetic field on the development of plaque in an artery with stenotic bifurcation. Consistent with existing literature, blood flow is characterized as a Newtonian fluid that is stable, incompressible, biomagnetic, and laminar. Additionally, it is assumed that the arterial wall is linearly elastic throughout. The hemodynamic flow within a bifurcated artery, influenced by an asymmetric magnetic field, is described using the arbitrary Lagrangian–Eulerian (ALE) method. This technique incorporates the fluid–structure interaction coupling. The nonlinear system of partial differential equations is discretized using a stable P2P1 finite element pair. To solve the resulting nonlinear algebraic equation system, the Newton-Raphson method is employed. Magnetic fields are numerically modeled, and the resulting displacement, velocity magnitude, pressure, and wall shear stresses are analyzed across a range of Reynolds numbers (Re = 500, 1000, 1500, and 2000). The numerical analysis reveals that the presence of a magnetic field significantly impacts both the displacement magnitude and the flow velocity. In fact, introducing a magnetic field leads to reduced flow separation, an expanded recirculation area near the stenosis, as well as an increase in wall shear stress.

In this paper, the fluid–solid interaction problem involving structural movement and deformation is considered, and an SPH (smoothed particle hydrodynamics) interaction method is proposed to establish a numerical fluid–solid model and to correct the particle velocities in the momentum conservation equations. It is found that, when the smoothing coefficient is equal to 0.93, the similarity of the free surface curves reaches up to 91.9%, and calculations are more accurate. Under the same working conditions, the classical model of elastic sluice discharge is established based on the SPH method and the finite element method, and the validity and accuracy of the model based on the SPH method are verified by analyzing the flow pattern of the sluice discharge, the opening of the elastic gate, and the change trend in the free liquid surface curve. On this basis, a number of characteristic points on the sluice gate are selected based on the SPH model to investigate the change rule of pressure at the fluid–solid interface, and the results are as follows: (1) based on the numerical model established by the SPH method, the flow pattern of the water, the opening of the elastic gate, and the change in the free liquid level curve are all in better agreement with the experimental results in the literature than those of the finite element method, and the computational results are also better; (2) the pressure of the solid on the fluid at each characteristic point is equal to the pressure of the fluid on the solid, which satisfies the principle of action–reaction and laterally verifies the nature of the dynamic boundary between the fluid and the solid, further verifying the validity of the program; and (3) in the process of sluice discharge, the elastic sluice presents a large force at both ends and a small force in the middle, meaning that the related research in this paper can act as a reference for flow–solid interaction problems related to sluice discharge. [ABSTRACT FROM AUTHOR]

The internal channel networks embedded within a soft structure can be a fruitful mechanism to create and activate actuators in the research fields of soft robotics. The deformation of the supporting elastic structure from the pressurized viscous fluid into the channels needs an accurate investigation. In this paper, accurate modeling and dynamic analysis of this nonlinear soft actuator is our goal. In this modeling, the soft actuator is considered the Euler-Bernoulli beam with large deflection and nonlinear strain. After implementing Hamilton's principle, the assumed mode method is used to achieve the mathematical model in terms of the multi-mode system that is more similar to the flexible nature of the actuation system. Steady-state dynamics is investigated by a combination of the complex averaging method with arc-length continuation. The accuracy of the proposed modeling is validated by comparing simulation results to those obtained with a nonlinear finite element method and numerical method. It shows that only one-third of the degree-of-freedoms used for the finite element method are sufficient to obtain equivalent converged solutions with the proposed model. The effect of nonlinear strain and multi-mode consideration in the analysis of the proposed modeling is investigated. It is advantageous to analyze the system performance by looking into the geometrical parameters and fluid properties. [ABSTRACT FROM AUTHOR]

Predicting the dynamical behavior of nanostructures in contact with fluid is of paramount importance owing to their vast range of applications in civil engineering, aerospace, etc. Therefore, the free vibration of a nonlocal Euler-Bernoulli beam in contact with fluid is studied in this research. Using the Navier-Stokes relation, the interaction forces between the fluid and nanobeam are obtained. The equation of motion is solved using the Galerkin method of weighted residuals, and the natural frequency values in different fluids are presented, considering the viscosity effect. Further, the fluid-solid interaction model on a macroscopic scale is compared with the finite element analysis results. By considering the fluid parameters to be zero, the results of the nonlocal beam have been validated with past research. According to the obtained results, when studying the vibration of nanobeams, while density has a remarkable impact on the reduction of nanobeam natural frequencies, the fluid viscosity can be neglected. The fluid has the greatest impact on lower modes, whereas the nonlocal parameter exerts the biggest influence on higher modes. Moreover, in all vibration modes, with the increase of the nonlocal parameter, the effect of the fluid on the reduction of the natural frequencies increases, and in the nanoscale, it has a more significant role in changing the vibrational behavior of the system compared to the classical condition. [ABSTRACT FROM AUTHOR]

• Innovative approach for water entry of multiple deformable bodies is provided. • Structures with arbitrary geometry are allowed to interact with each other. • Strong coupling among discrete flexible bodies and multiple fluids is achieved. • Accuracy and flexibility are demonstrated for 3D water entry problems. • Versatility of the method enables precise simulations of practical applications. In order to construct a versatile technique for water entry problems with structural deformations of multiple bodies, a novel hybrid algorithm, which couples the improved immersed boundary method (IBM) based fluid solver with the finite-discrete element method (FDEM) based structural solver, is proposed. The incompressible Navier-Stokes equations added with a virtual body force are employed for the hydrodynamic behaviors in the presence of elastic bodies. Representing the boundaries of solids by a set of immersed boundary points, the direct forcing IBM is enhanced to tackle the sharply moving objects of arbitrary geometries with inherent advantages. Such treatment enables the velocity boundary condition on the interface of the fluid and solid along with the divergence-free condition to be ensured simultaneously in the implicit computation of the added body force, which give rise to a more accurate depiction for fluid-solid interactions (FSI). Described by the finite element method (FEM), the deformable objects are allowed to deform and collide with each other during water entry which is seldom reported in literature. The contact interactions are calculated according to the distance potential function based discrete element method on the outermost layer of the finite elements. Furthermore, the improved conservative level set method is adopted to deal with the violently distorted free surface during hydroelastic impact. The strongly coupled FSI system is then resolved through a partitioned procedure, where sub-iterations are required in each time step to satisfy the convergence conditions exactly. The reliability of the present solver is validated by the classical cases of slamming of a flexible wedge and a free-falling cylindrical shell, along with dam break through an elastic gate and the settlement of two interactional circular cylinders. The accuracy and convergence rates of the proposed algorithm are also studied. Finally, a self-designed case, in which water entry of multiple compliant cylindrical shells is investigated, is performed to illustrate the effectiveness of the current approach, and a three-dimensional case study of multiple rocks impacting on the calm water surface demonstrates its great potential in practical applications. [ABSTRACT FROM AUTHOR]

Plate-shell integrated concrete liquid-storage structure (PSICLSS) has been widely applied with the development of water treatment technology. However, there are few anti-seismic performance and base-isolation design researches on it. The seismic performance of PSICLSS was studied, and the accuracy of finite element analysis was verified by experimental study. A calculation method of damping coefficient is proposed and used in a PSICLSS study. Based on 5 natural accelerations and 2 artificial accelerations, the dynamic responses of the isolation liquid storage structure under different peak ground acceleration are analyzed. The analysis results show that, non-isolated PSICLSS is easy to damage when subject to earthquake. The principal stress of the structure is maximum at the upper beam, and the maximum liquid hydrodynamic pressure appears at the connection position of the upper and lower conical shell. When the base isolation measure is used, the stress of the structure can be effectively reduced, but the liquid sloshing response will be magnified. With the increase of peak ground acceleration, the structural dynamic response and liquid sloshing response will increase. [ABSTRACT FROM AUTHOR]

The simulation of stationary acoustic fields involving thin porous layers is addressed in the present article. Layer thickness is assumed to be relatively thin in comparison to the overall computational domain, but its non‐negligible acoustic impact must be taken into consideration in the numerical model. Within the classical finite element method (FEM), meshes are compatible at material interfaces and the element distortions needs to be avoided. These requirements usually lead to an excessively costly spatial discretization for these problems of interest, as it forces mesh refinement surrounding the thin layer. This article provides a computational approach to relax this restriction. A generalized interface model derived from the plane wave transfer matrix Method (TMM) is established for modeling thin layers. We develop variationally consistent formulations to impose the interface conditions from models of thin layers for diverse coupling configurations, in which both acoustic fluid and poro‐elastic media are taken into account. The computational domain is discretized using the extended finite element method (X‐FEM) in order to introduce strong discontinuities in elements independently of the mesh. Implementation of the proposed formulations within X‐FEM is verified to be capable of providing accurate and robust solutions. The efficiency and flexibility of the present approach for multi‐layer and complex geometry problems are demonstrated compared to classical interface‐fitted finite element models through different simulation scenarios. [ABSTRACT FROM AUTHOR]

This paper presents an extension of the recently published quadrilateral finite element to analyze the free vibration of plates vibrating in air or interacting with the fluid. The previously proposed four-node element is based on the strain approach and the Reissner-Mindlin plate theory. The developed finite element, which contains the three essential external degrees of freedom at each of the four corner nodes, is based on assumed functions of the strain field that satisfy the compatibility equations. A comparison is presented with experimental and numerical data available in the literature to demonstrate the performance of the current element. The dynamic characteristics (natural frequencies and associated modes) of a rectangular plate simply supported or clamped totally submerged in water, a cantilever square plate, and a partially submerged vertical plate are numerically computed by the proposed element. The frequencies obtained by this element are of excellent accuracy compared to numerical, analytical, or experimental solutions from the literature. [ABSTRACT FROM AUTHOR]

In this study, the flagellar motility of a swimmer microorganism as a model of a human sperm cell, inside a two-dimensional channel as a model of the female reproductive tract containing a viscous fluid, is numerically investigated. The Navier–Stokes equations governing the fluid are coupled with the equations governing the models flagellum via applying a fluid–solid interaction approach and then solved using the finite element method. To stimulate the flagellum to move, a prescribed sinusoidal waveform is applied to it. The strain induced by this waveform along the flagellum initiates a continuous interaction between the flagellum and the fluid. The simulations are validated using data available in the literature. A very good agreement is seen between them. The results show that by decreasing the Young modulus of the flagellum as well as increasing the fluid viscosity, the swimming velocity of the model significantly decreases. It is found that for lower Young modulus of the flagellum, the effect of the fluid viscosity on the flagellar deformation is stronger. It is also found that for higher amplitude of the waveform applied to stimulate the flagellum, both the swimming velocity of the model and the average work rate are greater. Moreover, it is found that in a channel with a smaller height, the model swims at a higher speed and with a higher average work rate. [ABSTRACT FROM AUTHOR]

Bicuspid aortic valve (BAV) anatomy has routinely been considered an exclusion in the setting of transcatheter aortic valve implantation (TAVI) because of the large dimension of the aortic annulus having a more calcified, bulky, and irregular shape. The study aims to develop a patient-specific computational framework to virtually simulate TAVI in stenotic BAV patients using the Edwards SAPIEN 3 valve (S3) and its improved version SAPIEN 3 Ultra and quantify stent frame deformity as well as the severity of paravalvular leakage (PVL). Specifically, the aortic root anatomy of n.9 BAV patients who underwent TAVI was reconstructed from pre-operative CT imaging. Crimping and deployment of S3 frame were performed and then followed by fluid-solid interaction analysis to simulate valve leaflet dynamics throughout the entire cardiac cycle. Modeling revealed that the S3 stent frame expanded well on BAV anatomy with an elliptical shape at the aortic annulus. Comparison of predicted S3 deformity as assessed by eccentricity and expansion indices demonstrated a good agreement with the measurement obtained from CT imaging. Blood particle flow analysis demonstrated a backward blood jet during diastole, whereas the predicted PVL flows corresponded well with those determined by transesophageal echocardiography. This study represents a further step towards the use of personalized simulations to virtually plan TAVI, aiming at improving not only the efficacy of the implantation but also the exploration of "off-label" applications as the TAVI in the setting of BAV patients. Graphical abstract Computational frameworks of TAVI in patients with stenotic bicuspid aortic valve. [ABSTRACT FROM AUTHOR]

Summary: The coupled discrete element method and lattice Boltzmann method (DEMLBM) has increasingly drawn attention of researchers in geomechanics due to its mesoscopic nature since 2000. Immersed boundary method (IBM) and immersed moving boundary (IMB) are two popular schemes for coupling fluid particle in DEMLBM. This work aims at coupling DEM and LBM using the latest IBM algorithm and investigating its accuracy, computational efficiency, and applicability. Two benchmark tests, interstitial fluid flow in an ideal packing and single particle sedimentation in viscous fluid, are carried out to demonstrate the accuracy of IBM through semi‐empirical Ergun equation, finite element method (FEM), and IMB. Then, simulations of particle migration with relatively large velocity in Poiseuille flow are utilized to address limitations of IBM in DEMLBM modeling. In addition, advantages and deficiencies of IBM are discussed and compared with IMB. It is found that the accuracy of IBM can be only guaranteed when sufficient boundary points are used and it is not suitable for geomechanical problems involving large fluid or particle velocity. [ABSTRACT FROM AUTHOR]

A vessel's rudder interferes with the wake field of the composite propeller, which in turn affects not only the propulsion performance but also the structural deformation. To analyse the effect of the rudder on the composite propeller, a computational fluid dynamics (CFD) combined with finite element method (FEM)'s fluid–solid interaction (FSI) numerical method for calculating the composite propeller–rudder system (CPRS) was developed and verified. Analysis of the propulsion performance shows that the rudder can improve the propulsion efficiency of composite propellers. Such improvement also occurs with rigid propellers; however, the degree of efficiency improvement is higher for composite propellers. Analysis of structural deformation showed larger displacement; however, this does not lead to efficiency induction. The blade has a unique bend–twist coupling characteristics (i.e., the deformation of the bend is combined with a passive twist); changing the direction of the twist while changing the advance coefficient can improve efficiency. In addition, we analysed the effect of the propeller–rudder distance and the angle on the composite propellers. Considering energy saving and fatigue reduction, a propeller–rudder distance of 0.525D or an angle of 30° are favourable. • Rudder effect the propulsion performance and structural deformation. • Propose a numerical method for composite propeller–rudder systems. • Higher improvement in efficiency for composite propellers. • Changes in propeller–rudder parameter can improve performance. [ABSTRACT FROM AUTHOR]

Highlights • MHD mixed convection nanofluid in a vented cavity with elastic walls is studied. • At higher Re, when E changes both deterioration and enhancement of Nu is observed. • The number of vortices is reduced when the strength of the magnetic field is increased • Both deterioration and enhancement of average Nu is obtained with increasing Ha. • Generally, a reduction of Nu is achieved with increment in number of steps. Graphical abstract Abstract In this study, numerical analysis of mixed convection of CuO-water nanofluid in a cavity with inlet and outlet ports is performed under the effects of inclined magnetic field and step like corrugated elastic walls. The numerical simulation results are obtained by using finite element method. The Arbitrary-Lagrangian–Eulerian method is utilized for the description of the fluid motion with the elastic wall in the fluid-structure interaction model. In the current study, multiple step like corrugation of the wall is considered and it is made elastic which adds additional flexibility for the control of convective heat transfer features of the vented cavity. Effects of various pertinent parameters such as Reynolds number (between 100 and 500), Hartmann number (between 0 and 40), magnetic inclination angle (between 0° and 90°), elastic modulus of the flexible wall (between 5 × 104 and 108), number of step-like corrugation (between 1 and 8) and nanoparticle volume fraction (between 0 and 3%) on the fluid flow and heat transfer characteristics are numerically examined. It is observed that for higher value of Reynolds number, local Nusselt number both deteriorates and enhances in various locations along the hot wall whereas the changes in the local Nusselt number are marginal for lower value of Reynolds number. The multiple vortices in the vented cavity are influenced by the variation of magnetic field parameters and number of step like corrugation of the wall while the effects are not significant for the change of magnetic inclination angle. When the value of Hartmann number augments, the average heat transfer reduces until Hartmann number of 30 and increases for the highest value of Hartmann number. The average Nusselt number increment are in the range of 9-9.5% with the nanoparticle addition at the highest volume fraction in the absence and presence of magnetic field. Even though significant changes in the local Nusselt number are observed when the number of step like corrugation increases, it has a deterioration effect on the average heat transfer generally and 5.5% reduction in the average Nusselt number is obtained when the value is increased from 1 to 8. [ABSTRACT FROM AUTHOR]

Abstract Consequences of submarine landslides include both their direct impact on offshore infrastructure, such as subsea electric cables and gas/oil pipelines, and their indirect impact via the generated tsunami. The simulation of submarine landslides and their consequences has been a long-standing challenge majorly due to the strong coupling among sliding sediments, seawater and infrastructure as well as the induced extreme material deformation during the complete process. In this paper, we propose a unified finite element formulation for solid and fluid dynamics based on a generalised Hellinger–Reissner variational principle so that the coupling of fluid and solid can be achieved naturally in a monolithic fashion. In order to tackle extreme deformation problems, the resulting formulation is implemented within the framework of the particle finite element method. The correctness and robustness of the proposed unified formulation for single-phase problems (e.g. fluid dynamics problems involving Newtonian/Non-Newtonian flows and solid dynamics problems) as well as for multi-phase problems (e.g. two-phase flows) are verified against benchmarks. Comparisons are carried out against numerical and analytical solutions or experimental data that are available in the literature. Last but not least, the possibility of the proposed approach for modelling submarine landslides and their consequences is demonstrated via a numerical experiment of an underwater slope stability problem. It is shown that the failure and post-failure processes of the underwater slope can be predicted in a single simulation with its direct threat to a nearby pipeline and indirect threat by generating tsunami being estimated as well. [ABSTRACT FROM AUTHOR]

Based on the work of Monk and Selgas (2022), we explore the finite element method for the modified transmission eigenvalues for inverse scattering in a fluid–solid interaction problem. Under minimal regularity on the solution, we give a complete error analysis including the a priori and the a posteriori error estimates. We also present adaptive computations. [ABSTRACT FROM AUTHOR]

Tubing string is one of the most important tools in flowing production. In the state of lateral vibration instability of the tubing string, severe collisions between the string and casing may lead to tubing string failure and borehole wall sloughing. Stability of the tubing string is a potential safety hazard in the process of oil and gas production and discussed in this paper. Considering interaction among the gravity, internal fluid hydrodynamic force, reservoir pressure and liquid cushion in the annular, a mechanical model of lateral vibration of the tubing string, which is simplified as a uniform pipe conveying fluid upwards in vertical well, is developed, and the stability of the system is analyzed by the finite element method. The influences of the flow velocity, the bottom hole pressure and the height and density of liquid cushion on the stabilities of tubing string are discussed. It is found that the increase of either the flow velocity or the bottom hole pressure can cause the buckling of tubing string, however, increasing the height or density of liquid cushion is helpful to improve the stability of tubing string. [ABSTRACT FROM AUTHOR]

The paper presents the numerical simulation technology of deep-water risers' fluid-solid interaction based on mesh-free MLPG method, which applies the combination of Petrov-Galerkin Method and three-step finite element method in the mode of separating velocity and pressure to discretize control equation of two-dimensional incompressible flow field respectively in time and space. At the end of the paper, a stationary cylinder Vortex-Induced Vibration is taken as an example to be calculated and compared. It is in good agreement with the traditional numerical method based on mesh and physical model well, which proves the proposed method is effective and has good accuracy. [ABSTRACT FROM AUTHOR]

We propose an implicit Newmark method for the time integration of the pressure-stress formulation of a fluid-structure interaction problem. The space Galerkin discretization is based on the Arnold-Falk-Winther mixed finite element method with weak symmetry in the solid and the usual Lagrange finite element method in the acoustic medium. We prove that the resulting fully discrete scheme is well-posed and uniformly stable with respect to the discretization parameters and Poisson ratio, and we provide asymptotic error estimates. Finally, we present numerical tests to confirm the asymptotic error estimates predicted by the theory. [ABSTRACT FROM AUTHOR]

Towoard the bearing capacity design issue for the stirring shaft， the torque， deformation and the stress situations were studied based on computational fluid dynamic simulation and fluid-structure interaction analysis by working with various viscosity materials， for the multi-layer stirring and fermentation machine for high viscosity material. The strength-safe viscosity limits and range are calculated according to the torque force of the stirring device， as well as the torque of stirring device under different filling height was analyzed. The results indicated that the on-paddle torque in the first layer is the largest， and the largest deformation happens in the finally the sixth layer. Besides the maximum stress occurs in the shaft segment between the short shaft and the first layer stirring paddle. The safe viscosity limit is 205Pa·s. The height variation of the filling material has little effect to the torque in the stirring device and the optimum heitht range is 100~150mm from the material surface to the top of stirring tank. [ABSTRACT FROM AUTHOR]

We present a convergence analysis for the space discretization via a dual-mixed formulation of a time-dependent system of partial differential equations modeling an elastoacoustic interaction problem. The resulting unknowns are given by the stress tensor in the solid and the pressure in the fluid, so that the Arnold-Falk-Winther mixed finite element method with weak symmetry in the structure and the usual Lagrange finite element method in the acoustic medium are employed to define the associated semidiscretization. We analyse the resulting global semidiscrete scheme by introducing here for the first time an adequate projector and its discrete counterpart and by estimating the error between them. We show that the method is stable uniformly with respect to the space discretization parameter and the Poisson modulus, and derive the corresponding asymptotic error estimates. In addition, our approach allows the postprocessing of the displacement and the velocity with analog convergence results. [ABSTRACT FROM AUTHOR]

The simulation of interaction between flow and the elastic structure is a complicated fluid-solid interaction problem, involving the structure's large deformation and fluid interface variation. In this paper, an adaptive CIP (constrained interpolation profile)-based numerical model has been presented to simulate this problem. In this CIP-based model, the constrained interpolation profile method, a high-order finite difference method, is employed as the base flow solver and THINC/SW (Tangent of Hyperbola for Interface Capturing with Slope Weighting) method, a volume of fluid method, is applied to capture the flow interface. IBM (immersed boundary method) method is used to treat the fluid-solid interface. The body deformation is calculated by coupled FDM-FEM (finite difference method and finite element method) method. Adaptive mesh is generated by Afivo (Adaptive Finite Volume quadtree/Octree mesh) framework. The cases of flow past a square and water entry of a symmetric solid wedge are carried out to validate the reliability of the flow solver in this present model. Cantilever beam deformation case is used to validate the accuracy of the solid solver in the present model. Then cases of a thin elastic beam in sloshing tank and dam-break flow are carried out by using this model. After that, the case of regular wave past a membrane breakwater is studied. Our numerical results are compared with previous experimental and numerical studies, and good agreements are obtained. It is demonstrated that this present numerical model has good applicability to simulate the interaction between flow and a thin elastic beam. • A coupled fluid-solid numerical model is proposed to simulate the interactions between the fluid and a thin elastic beam. • CIP numerical method can solve free surface flow problems dominated by convection term with high accuracy. • Afivo adaptive mesh framework can track the boundary of the moving body and calculate the flow field in parallel. • Immersed boundary method is modified and can increase the accuracy of velocity at the interface. • Results shows that this numerical model with adaptive mesh is proved to be an effective tool for numerical simulations. [ABSTRACT FROM AUTHOR]

A numerical model is developed for investigation of coupled dynamics of fuel contained elastic launch vehicles in planar atmospheric flight. Finite element method along with the linear quasi-steady piston aerodynamic theory is used for developing an aeroelastic model. A reduced order boundary element model is used for modeling the liquid sloshing in tanks. The interaction of sloshing and aeroelasticity is studied using stability analysis of the coupled system. Results show that the slosh–aeroelastic coupling in an elastic launch vehicle occurs for low tank filling ratios and may lead to decreasing the system damping. Due to more interactions between the slosh and rigid body modes, larger damping values of the rigid body mode and lower slosh frequencies are found for an elastic vehicle compared with a rigid vehicle. It is also shown that the slosh–aeroelastic interaction is increased as the slosh inherent damping decreases. [ABSTRACT FROM AUTHOR]

The concentrated wind energy device is the core of the wind energy concentration generator, so the material choice of the former can influence directly the widespread application of the latter. This research adopts a fluid-solid interaction(FSI) method to study the viability of using organic glass to manufacture concentrated wind energy devices. The Poisson’s ratio, Young’s modulus and fracture stress of organic glass change with the temperature. Therefore, the wind pressure distribution on the surface of the concentrated wind energy device is worked out when air flows at the speed of 25 m/s at different temperatures under normal atmospheric pressure. Then, the maximum equivalent stress and the maximum deformation can be also worked out when the wind pressure distribution is loaded on the concentrated wind energy device at the corresponding temperature. So at first, a solid-field model of a concentrated wind energy device is created based on the size of the model by using the computer aided design(CAD) software. And the solid-field model is imported into the finite element analysis software and a cylinder is established, and the cylinder and the solid field have the same axial line. The radius of the cylinder is 10 m and the height is 30 m. The distance between the inlet of the fluid-field area and the bottom surface of the concentrated wind energy device is 5 m. Then through Boolean subtraction method, a geometric fluid field is established by subtracting the solid field area in the cylinder. With the help of the computational fluid dynamics(CFD) software, the fluid field is simulated and calculated in a specific wind field. A non-uniform tetrahedron meshing and an SST k-ω turbulence model are adopted. The fluid medium is air and the pressure is always 101325 Pa. The temperatures are 233.15, 243.15, 253.15, 263.15, 273.15, 283.15, 293.15, 303.15 and 313.15 K respectively. The density, the thermal conductivity coefficient, the constant-pressure specific heat capacity and the viscosity correspond to the pressure of 101 325 Pa and the temperature. And the mass flow rate, turbulent kinetic energy and specific dissipation rate can be calculated from the density, viscosity and size of fluid field. When the temperature is 293.15 K, the density, viscosity, thermal conductivity coefficient, constant-pressure specific heat capacity, mass flow rate, turbulent kinetic energy and specific dissipation rate are respectively 1.2054 kg/m3, 1.86×10-5 kg/(m·s), 0.02593 w/(m·K), 1013 J/(kg·K), 9 464.048 kg/s, 0.686 m2/s2 and 24 s-1. The mass flow inlet and pressure flow outlet are adopted. The surface roughness height of the concentrated wind energy device is set to 0.3 mm. When the component residual reaches 1.0×10-4 kg/s, the equation converges and the distribution of the wind speed and wind pressure in the fluid field under different temperatures are obtained. The diagram of wind speed distribution shows that, when the temperature is 293.15 K, the average wind speed inside the central cylinder exceeds 25 m/s. This indicates that the concentrated wind energy device has increased wind speed and concentrated the energy. In the structural static module, the solid field, as a whole, is split into tetrahedral meshes, and the size of the structural unit is 0.005 m. When the calculated results of the fluid field are loaded on the concentrated wind energy device, the stress cloud plot and the solid-field deformation plot are obtained. The plots show that, when the temperature is 293.15 K, the maximum stress is on the back of the outer edge of the shrinkable pipe, with a maximum stress of 1.5378 MPa, far less than the fracture stress of candidate organic glass of 71.704 MPa. And the maximum equivalent deformation is 3.0995 mm. Therefore, it is concluded that organic glass can be used as the material of the concentrated wind energy device. Meanwhile, the analytical process can provide the references for the analysis of probability of producing concentrated wind energy devices with the material whose mechanical properties change with temperature change. [ABSTRACT FROM AUTHOR]

In this paper, a fluid–solid interaction algorithm is developed to study the interaction between a collapsing bubble and a deformable viscoelastic solid, which is accomplished by coupled boundary-element (BE) and finite-element (FE) calculations incorporating a Zener type viscoelastic model. The boundary-element method (BEM) is used to simulate the physical process of bubble growth, contraction and collapse while the finite element method (FEM) is used to calculate the viscoelastic solid response to the impulsive pressure induced by the bubble collapse. The implementation of the Zener type viscoelastic model is critical for this study to accommodate the stiffness variation of a viscoelastic solid with time under the pressure. The study reveals the effects of the viscoelastic properties, different maximum bubble sizes and bubble locations on the dynamic response of the viscoelastic solid. Interesting insights into the complex problem of the interaction between a collapsing bubble and a deformable viscoelastic solid are obtained, which can be useful for potential application in biomedicine or marine industry. [ABSTRACT FROM AUTHOR]

A fully coupled mathematical model of land subsidence caused by groundwater pumping was established based on the mechanics of porous seepage and the theory of fluid-solid interaction. The mathematical model employing the Galerkin finite element method was proposed to simulate the deformation dependencies of hydraulic properties due to the water pressure decrease in aquifers. This model has been verified by comparing with the known analytical solutions in the confined aquifer. Results show that the simulated drawdown and displacements match well with those of analytical solutions. To evaluate the nonlinear effects of hydraulic properties in the seepage and consolidation coupling phenomena, the numerical model is applied to an ideal three layers numerical experiment. The results show that the subsidence rate is faster than conventional groundwater theory when the nonlinear hydraulic properties (NHP) are considered in the coupled model. The reason is that the water level decline due to groundwater withdrawal induces the soil compression and the porosity and permeability decrease. Decrease of permeability in regions adjacent to the pumping well produces hydraulic gradient and seepage forces that may result in accelerated subsidence. Therefore, the effect of the NHP is an interaction process of pore water pressure and soil consolidation deformation and should not be ignored. Further studies of various hydrogeology problems are recommended to consider the heterogeneity concerning different stratigraphic condition in the field. [ABSTRACT FROM AUTHOR]

A numerical framework to model and simulate gas–liquid–solid three-phase flows is proposed and implemented in this work. The overall algorithm adopts a non-boundary-fitted approach that avoids frequent mesh-updating procedures by defining independent meshes and explicit interfacial points to represent each phase. Here, we couple our existing solvers, the immersed finite element method (IFEM) and the connectivity-free front tracking (CFFT) method that model fluid–solid and gas–liquid interactions, respectively, for the three-phase models. A modified IFEM algorithm is derived for modeling fluid–solid interactions that accounts for the dynamics of the solid, while the CFFT is used here to simulate gas–liquid multi-fluid flows that uses explicit interfacial points to represent the gas–liquid interface and for its easy handling of interface topology changes. Instead of defining different levels simultaneously as used in level sets, an indicator function naturally couples the two methods together to represent and track each of the three phases. Several 2-D and 3-D testing cases are performed to show the robustness and capability of the coupled numerical framework in dealing with complex three-phase problems, in particular free surfaces interacting with deformable solids. [ABSTRACT FROM AUTHOR]

The concentrated wind energy device is the core of the concentrated wind energy generator, and its material can directly affect the widespread application of the concentrated wind energy generator. This research adopts a fluid-solid interaction (FSI) method. At first, a solid-field model of a concentrated wind energy device is created with the help of the CAD software according to the size of the model. And a cylindrical area is established after the solid-field model is imported into the finite element analysis software. The cylindrical area has a radius of 10 m and a length of 30 m and the distance between the inlet of the fluid-field area and the inlet of the concentrated wind energy device is 5 m. Then in the cylindrical area, a geometric fluid field is established through Boolean subtraction of the solid field area. Based on the CFD software analysis of the fluid field, the wind flow is simulated in a specific wind field. A non-uniform tetrahedron meshing and an SST k-ω turbulence model are adopted. The fluid medium is air, with the temperature of 296.75 K, the density of 1.044 kg/m3, the pressure of 88 800 Pa, the viscosity of 1.85×10-5 kg/(m∙s), the thermal conductivity coefficient of 0.02623 W/(m∙K), and the constant-pressure specific heat capacity of 1 013 J/(kg∙K). During the simulation, the wind speed is set to 25 m/s, the mass flow rate is set to 8199.557 kg/s, and the corresponding turbulent kinetic energy and the specific dissipation rate are respectively 0.714963 m2/s2 and 24.67 s-1. The mass flow inlet and pressure flow outlet are adopted. The roughness height of surface is set to 0.3 mm. When the component residual reaches 1.0×10-4 kg/s, the equation converges and the distribution of the wind speed and wind pressure in the fluid field is obtained. The result shows that the maximum wind speed that the central cylinder can work on the wind turbine blades is 35 m/s and the fluent speed increases along the radial direction of the wall, with a maximum speed of 38.8 m/s at the central cylinder. This indicates that the concentrated wind energy device has increased wind speed and concentrated its energy. In the structural static module, the whole solid field is divided into tetrahedral meshes and the size of each structural unit is 0.02 m. The stress cloud plot and the solid-field deformation plot are obtained after the calculated results of the fluid field are loaded on the concentrated wind energy device. The plots show that the maximum stress area is on the outer edge of the diffusion pipe with a maximum stress of 3.267 MPa, which is far less than the yield strength of 66 MPa, the fracture stress of 65 MPa and the bending strength of 98 MPa in the candidate German Bayer's makrolon-2407 polycarbonate. Therefore, it is concluded that this type of polycarbonate can be used to make the concentrated wind energy device. Meanwhile, the results of the analysis can provide theoretical basis and reference for the later structural improvement and design optimization. [ABSTRACT FROM AUTHOR]

SUMMARY We describe a hybrid method to study fluid and solid interaction problems in the frequency domain. The numerical method is based on subdomain decomposition. The BEM is used to model unbounded solid mediums, whereas the confined subdomains, both fluid and solid, are represented by the FEM. The analysis is carried out by superposing two-and-a-half dimension (2.5D) problems for different longitudinal wave numbers. A novel 2.5D FEM formulation for inviscid fluids is proposed, which include the energy lost at the fluid boundary enclosure. The fluid and solid subdomains are coupled, and appropriate boundary conditions are imposed at the interfaces. The proposed technique is verified from analytical solutions. A cylindrical cavity located in an unbounded solid medium excited by a dilatational point source is studied. Computed results are in good agreement with the analytical solution. Later, noise and vibration in a concrete tunnel due to an internal pressure load is analysed with the proposed methodology. Results show that tunnel and soil displacements increase with the load speed, as did the air pressure inside the tunnel, according with the travelling ranges defined by the wave propagation velocities in each medium. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In view of fluid flow in cracks and rock deformation, the mathematical model for shale hydraulic crack propagation was established. The crack flow field and the rock stress field were solved with the finite element method and the extended finite element method respectively, and the two fields were coupled through the Picard iteration. The presented model gave results consistent with those of the classic model, which verified correctness of the former. Based on the model, the effects of the rock elasticity modulus, Poisson's ratio and injection rate on the crack geometry, and the dynamic process of a hydraulic crack approaching a natural crack at an arbitrary angle, were simulated. The numerical results show that the elasticity modulus and injection rate have significant influence on the crack geometry, while the Poisson's ratio has little effect; the more brittle the shale is, the longer and narrower the hydraulic crack will grow; the greater the principal stress difference and the approaching angle are, the easier the hydraulic crack crosses the natural crack; there is a relatively large decrease in the crack width at the intersection between a hydraulic crack and a natural crack; the extended finite element method avoids mesh reconstruction and refinement during computation, and reduces the computing time. The presented model provides an effective theoretical tool for the shale fracturing design. [ABSTRACT FROM AUTHOR]

SUMMARY A Discontinuous Galerkin (DG)-based approach is proposed for computing the scattered field from an elastic bounded object immersed in an infinite homogeneous fluid medium. The proposed method possesses two distinctive features. First, it employs higher-order polynomial-shape functions needed to address the high-frequency propagation regime. Second, it is equipped with curved boundary edges to provide an accurate representation of the fluid-structure interface. The most salient benefits resulting from the latter feature, as demonstrated by the numerical investigation, are the following: (i) an improvement by-at least-two orders of magnitude on the relative error and (ii) the disappearance of spurious resonance frequencies in the surrounding fluid medium. In addition, the reported numerical results reveal that when using cubic polynomials with less than three elements per wavelength, the proposed DG method computes the scattered field with a relative error below 1% for an elastic scatterer of about 30 wavelengths. This observation highlights the potential of the proposed solution methodology for efficiently solving mid-frequency to high-frequency elasto-acoustic scattering problems. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Deformation of underground rocks, also named rock creep, is treated as porous materials which usually results in many engineering problems, especially in petroleum engineering. However, it can be controlled by fluid-solid interaction in porous materials, and the deformation mechanism of underground rocks with fluid-solid interaction was analysed by finite element computing method. Specifically, an Iterative computing method and a computational procedure of two-way fluid-solid coupling are used to simulate deformation process until the fluid and solid solution variables are fully coupled. A typical application example was taken in Jinzhou oil production plant of Liaohe Oil Field Company, and a finite element model is built by combined application of parasolid and native modelling methods. According to the calculation results, deformation mechanism of underground rocks is proposed, and some advice is also presented. [ABSTRACT FROM AUTHOR]

Abstract: Endotracheal stenting is a controversial treatment for tracheal stenosis. Metallic stents have advantages but also show disadvantages such as restenosis due to epithelial hyperplasia and granuloma formation. In this work we analyze the response of a rabbit tracheal wall during normal breathing under implantation of a Zilver® Flex™ Stent. Trachea geometries were reconstructed using medical images for both healthy and stented rabbit. The numerical model was used for analyzing tracheal stresses before and after prosthesis implantation using a fluid–structure interaction approach (FSI). Unstructured tetrahedral-based grids were used to perform the simulations with a finite element-based commercial software code. Experimental tests on rabbit trachea samples were performed in order to get the material property constants. Deformations of the tracheal cartilage rings and of the muscular membrane as well as the maximum principal stresses of the tracheal wall were analyzed and compared with those of the healthy trachea in absence of prosthesis. In addition, an experimental validation of the model was provided. The prosthesis was percutaneously implanted under fluoroscopic control. Period of the study was 90days. The tracheal wall response was assessed by means of computerized tomography by endoscopy, macroscopic findings and histopathological study. Experimentally revealed tissue damages due to the stent were then compared with numerical results. Interesting correlation with maximal principal stresses and induced wall shear stress were found in the same region. [Copyright &y& Elsevier]

To reduce the pressure shock of the electro-hydraulic-servo piston hydraulic transformer with swash plate, to lower the noise and to improve the operational stability, this paper develops buffer slot in the valve plate of the hydraulic transformer based-on the fluid-structure coupling function of the software ADINA. In software Pro/E, fluid model and solid model of the flow assignment structure of valve plate are built and imported to the software ADINA for building of finite element model. The flow field of the flow assignment structure that was checked with finite element method was analyzed. A valve plate with buffer slot with triangle shape was manufactured and tested on hydraulic transformer test-bed. The results revealed that the valve plate enabled hydraulic transformer steady in operation and the minimum speed of hydraulic transformer reached 35 r/rain. The noise was lower and the reliability was improved. The correctness of theoretical analysis was testified. [ABSTRACT FROM AUTHOR]

Abstract: This work presents a detailed methodology for comprehensive crashworthiness analysis of hybrid or composite structures jet engine forward sections when subjected to soft impact. Effective strategies are developed within an explicit finite element framework for modeling a bird, intra-ply and inter-ply composite damage, and hybrid structural failure. These techniques are then combined to form a full multiphysics, multiscale crashworthiness analysis methodology. Hybrid fan blade fracture, leading edge de-bonding, composite casing delamination, and other progressive damage effects are captured. The methods developed thus far have the potential to accurately capture the full spectrum of forward section impact damage. [Copyright &y& Elsevier]

Dispersive properties of elastic waves in a periodic composite with an array of fluid-filled holes are studied in this paper. A finite element method taking into account of the fluid-solid interaction is developed to calculate the dispersion curves. The finite element formulation is presented for one unit cell by taking advantage of the periodicity of the structures and the Bloch theorem. After dividing the equations in the real and imaginary parts, the numerical computation is performed by using the standard finite element code ABAQUS. As numerical examples, some typical two- and three-dimensional systems with circular or spherical holes filled with air, water or mercury are considered in detail. The method can yield precise results with fast convergence for all cases from very low-density fluids to very high-density fluids. [ABSTRACT FROM AUTHOR]

The resistance loss of transportation was studied and the influences of buoyancy layout, mineral content and elastic modulus of flexible hose were investigated based on three-dimensional finite element model of fluid-solid interaction by MSC.MARC/MENTAT software. The numerical results show that the resistance losses increase with the increase of mineral content C and velocity of internal fluid v and decrease with the increase of elastic modulus E of flexible hose. The buoyancy layout and the velocity of internal fluid have greater impacts on the resistance losses than the elastic modulus of flexible hose. In order to reduce the resistance losses and improve the efficiency of the deep-ocean mining, C and v must be restricted in a suitable range (e.g. 10%-25% and 2.5-4 m/s). Effective buoyancy layout (such as Scheme C and D) should be adopted and the suitable material of moderate E should be used for the flexible hose in deep-ocean mining. [ABSTRACT FROM AUTHOR]

Abstract: The Dumon silicone stent is widely used in human medicine for treating tracheal diseases. Although presenting many advantages, as its facility of positioning and removing and its relative low cost, commonly reported complications include stent migration, inflammatory granulation tissue formation, and obstruction. Taking into account this last aspect, in this work we propose an improved stent design which may help in preventing episodes of mucous accumulation. In particular, we changed the design of the stent extremities in order to improve the flow field which cyclically crosses the prosthesis. To evaluate the performances of this new design, a finite element model of a human stented trachea was developed using a fluid–structure interaction approach (FSI). The geometry of the trachea is obtained from computed tomography (CT) images of a healthy patient. The simulations were performed using a finite element-based commercial software code. The tracheal wall is modeled as a fiber reinforced hyperelastic solid material in which we introduced the anisotropy due to the orientation of the fibers. Different new prosthesis designs were tested. Results showed that linear and parabolic transitions of the top and bottom stent extremities reduce the local vorticity field preventing high local flow recirculations during breathing. [Copyright &y& Elsevier]

An integrated fluid-thermal-structural analysis approach is presented. In this approach, the heat conduction in a solid is coupled with the heat convection in the viscous flow of the fluid resulting in the thermal stress in the solid. The fractional four-step finite element method and the streamline upwind Petrov-Galerkin (SUPG) method are used to analyze the viscous thermal flow in the fluid. Analyses of the heat transfer and the thermal stress in the solid are performed by the Galerkin method. The second-order semiimplicit Crank-Nicolson scheme is used for the time integration. The resulting nonlinear equations are linearized to improve the computational efficiency. The integrated analysis method uses a three-node triangular element with equal-order interpolation functions for the fluid velocity components, the pressure, the temperature, and the solid displacements to simplify the overall finite element formulation. The main advantage of the present method is to consistently couple the heat transfer along the fluid-solid interface. Results of several tested problems show effectiveness of the present finite element method, which provides insight into the integrated fluid-thermal-structural interaction phenomena. [ABSTRACT FROM AUTHOR]

Abstract: Endotracheal stenting is a common treatment for tracheal disorders as stenosis, cronic cough or dispnoea episodes. However, medical treatment and surgery are still challenging due to the difficulties in overcoming potential prosthesis complications. In this work we analyze the response of the tracheal wall during breathing and coughing conditions under different stent implantations. A finite element model of a human trachea was developed and used to analyze tracheal deformability after prosthesis implantation under normal breathing and coughing using a fluid-structure interaction approach (FSI). The geometry of the trachea is obtained from computed tomography (CT) images of a healthy patient. A structured hexahedral-based grid for the tracheal wall and an unstructured tetrahedral-based mesh with coincident nodes for the fluid were used to perform the simulations with a finite element-based commercial software code. Tracheal wall is modeled as a fiber reinforced hyperelastic solid material in which the anisotropy due to the orientation of the fibers is taken into account. Deformations of the tracheal cartilage rings and of the muscle membrane, as well as the maximum principal stresses in the wall, are analyzed and compared with those of the healthy trachea in absence of prosthesis. The results showed that, the presence of the stent prevents tracheal muscle deflections especially during coughing. In addition, we proposed a methodology to evaluate, through numerical simulations, the predisposition of the stent to migrate. [Copyright &y& Elsevier]

The study on the mechanism and performance of the mechanical seals in reactor coolant pumps (RCPs) is very important for the safe operations of pressurized water reactor power plants. By exploring the operating mechanism of the first seal of the hydrostatic mechanical seal in RCPs, an analytical fluid–solid strong-interaction model of the seal is proposed in this article. The model holds that the mechanical deformations of the seal assembly are dominated by the deflections of the seal rings, and this idea is demonstrated by the numerical simulation result of a fluid–solid interaction (FSI) model. Using the analytical FSI model, the regularity that the leakage rate of the first seal varies with the differential pressure in a RCP is obtained, and compared with the operational data, which is used to verify the model. Based on the understanding of the reliability of the seal, a dimensionless parameter Λ that acts as an attribute to the reliability is proposed in this article. Using the analytical FSI model and Λ as the optimization algorithm and optimization object, respectively, the optimum designs about the seal faceplateconfigurations are performed. Also, the specific optimization conclusions are given simultaneously. [ABSTRACT FROM AUTHOR]

This paper deals with a fluid–solid interaction problem inspired by a biomechanical brain model. The problem consists of determining the response to prescribed static forces of an elastic solid containing a barotropic and inviscid fluid at rest. The solid is described by means of displacement variables, whereas displacement potential and pressure are used for the fluid. This approach leads to a well-posed symmetric mixed problem, which is discretized by standard Lagrangian finite elements of arbitrary order for all the variables. Optimal-order error estimates in the H1- and L2-norms are proved for this method. A residual a posteriori error estimator is also proposed, for which efficiency and reliability estimates are proved. Finally, some numerical tests are reported to assess the performance of the method and that of an adaptive scheme based on the error estimator. [ABSTRACT FROM PUBLISHER]