Structure Interaction Problems Research Articles

Coupling of stabilized total Lagrangian and weakly compressible SPH models for challenging fluid–elastic structure interaction problems

Coupling of stabilized total Lagrangian and weakly compressible SPH models for challenging fluid–elastic structure interaction problems

A coupled smoothed particle hydrodynamics-finite volume method for three-dimensional modeling of bubble dynamics

Bubble pulsation is a characteristic multiphase compressible flow, which involves periodic oscillation and strong pressure wave and is vulnerable to boundary conditions. The smoothed particle hydrodynamics (SPH) has limitations in imposing the fluid boundary suitable for such problems, which have been verified first with the state-of-the-art SPH boundaries. It brings challenges to the three-dimensional modeling. Then, we propose to combine SPH with the finite volume method via the spatial coupling to deal with this problem. The accuracy of the coupled method has been validated by comparisons with other numerical methods and the theoretical equation from the spherical pulsation to the more complex bubble oscillations. Good agreements are obtained in terms of the bubble radius and the pulse pressure peak. The conclusions drawn in this work and the computational framework lay the foundation for the further complicated study on the bubble dynamics, the complete process of underwater explosion, and the related fluid–structure interaction problems.

Poiseuille-Type Approximations for Axisymmetric Flow in a Thin Tube with Thin Stiff Elastic Wall

An asymptotic ansatz for the solution of the axisymmetric problem of interaction between a thin cylindrical elastic tube and a viscous fluid filling the thin interior of the elastic tube was recently introduced and justified by G. Panasenko and R. Stavre. The thickness of the elastic medium (ε) and that of the fluid domain (ε1) are small parameters with ε<<ε1<<1, while the scale of the longitudinal characteristic size is of order one. At the same time, the magnitude of the stiffness and density of the elastic tube may be large or finite parameters with respect to the viscosity and density of the fluid when the characteristic time is of order one. This ansatz can be considered as a Poiseuille-type solution for the fluid–structure interaction problem. Its substitution to the Stokes fluid–elastic wall coupled problem generates a one-dimensional model. We present a numerical experiment comparing this model with the solution of the full-dimensional fluid–structure interaction problem.

Combined Micro-Structural Effects of Linearly Increasing Reynolds Number and Mean Inflow Velocity on Flow Fields with Mesh Independence Analysis in Non-Classical Framework

The monolithic Eulerian formulation has widely been employed for solving numerically fluid–structure interaction (FSI) problems of finite structural displacement using the same mathematical variational formulation for fluid and structural dynamics. Recently, different physical features of fluid flow have been analyzed using this approach to such coupling problems by computing the classical benchmark solutions in a non-classical framework. Despite producing decent results, the analysis of micro-structural characteristics of fluid flow by applying the classical benchmark solutions still needs to be enhanced and extended further for such coupling problems. In this paper, the classical benchmark solutions have been enhanced and extended further for analyzing the combined micro-structural effects of linearly increasing Reynolds number Re and mean inflow velocity U¯ on flow fields with mesh independence analysis by employing a monolithic Eulerian formulation in a non-classical framework. To this aim, the Cosserat fluids theory is taken into account for the present coupling problem by considering three micro-rotational degrees of freedom (dof) of fluid particles. The model equations of the proposed Cosserat fluid–structure interaction (CFSI) problem are derived using underlying laws of continuum mechanics. A numerical section presents the implementation of the benchmark problem with test examples followed by a detailed evaluation of the obtained results. The results obtained indicate that a uniform linear increase in Reynolds number Re and mean inflow velocity U¯ produce the significant combined micro-structural effects on the micro-rotation velocity field ω, and this effect is found increasing on the increase of both parameters. This combined effect of increasing Re and U¯ on the velocity field u is also observed to be very significant in a sense that horizontal and vertical flow velocity profiles experience great variation by maintaining the same pattern on each increasing value of Re and U¯ at any particular location in the computational domain. Further, the mesh independence analysis is employed to verify the convergence of obtained results. The study concludes that the linear increase in Reynolds number and mean inflow velocity affect micro-rotational velocity field significantly at the micro-structural level with mesh independence analysis. Finally, some future recommendations to enhance and extend the study with some of its limitations are presented.

Regularized SPH model for soil–structure interaction with generalized frictional boundary

AbstractThis paper proposes a regularized smoothed particle hydrodynamics (SPH) scheme to solve the problems of tensile instability and stress noise in large‐deformation soil–structure interaction. Particle shifting and stress regularization are combined to maintain uniform stresses and particle distributions. A generalized frictional boundary condition is presented to model soil–structure interfaces with abitrary friction coefficients. A modified particle shifting technique is developed to regularize particles near the frictional boundaries. Furthermore, GPU acceleration algorithm is adopted to improve the efficiency. The proposed scheme is compared with the conventional SPH methods using numerical examples, including the collapse of three‐dimensional granular column, the collapse of the cohesive soil, and pipe penetrates into soft clay. The comparison indicates that the proposed regularized SPH model can give highly accurate results for large‐deformation soil–structure interaction problems with arbitrary friction coefficient.

Shape Sensitivity Analysis of a 2D Fluid–Structure Interaction Problem

We study the shape differentiability of a general functional depending on the solution of a bidimensional stationary Stokes–elasticity system with small loads, with respect to the reference domain of the elastic structure immersed in a viscous fluid. The differentiability with respect to reference elastic domain variations is considered under shape perturbations with diffeomorphisms. The shape derivative is then calculated with the use of the velocity method. This derivative involves the material derivatives of the solution of this fluid–structure interaction problem. The adjoint method is then used to obtain a simplified expression for the shape derivative.

A coupled peridynamics–smoothed particle hydrodynamics model for fracture analysis of fluid–structure interactions

In this paper, a numerical model that couples peridynamics (PD) with smoothed particle hydrodynamics (SPH) is presented for fracture modeling in fluid–structure interaction (FSI) problems. PD was employed to simulate the solid structure fracture because of its ability to deal with discontinuity problems. SPH was applied to simulate the fluid behavior because of its advantages in modeling free-surface flows. A virtual particle layer was established in the fluid–structure interfacial region to ensure the force and deformation transfer between the fluid and solid phases. Validation was performed qualitatively and quantitatively through simulations of classical benchmark tests. The SPH model of the free-surface flow, the PD model of the solid structure, and the coupled PD-SPH model of the FSI were carefully verified. It was demonstrated that the results matched the experimental observations well, with a maximum error of less than 10%. The hydraulic fracture of a gravity dam and the impact of dam-break flow on a baffle were simulated as applications of the coupled PD-SPH model. The predicted crack path in the gravity dam agreed closely with the experimental observations, with a Pearson correlation coefficient of 0.9983. A preliminary extension of the proposed PD-SPH model to three dimensions is also presented, and its performance was evaluated. The results indicate that the coupled model is accurate in modeling the solid fracture process in FSI problems.

Fluid–structure interaction simulation of a flapping flag in a laminar jet

The flapping flag is a classical and important Fluid–Structure Interaction (FSI) problem with many applications in nature, industry, and biological systems. However, the interaction between the flow field and the flag response is not fully understood due to the complex and nonlinear nature of the problem. Although theoretical models qualitatively predict the flapping frequency and the onset velocity, there are still quantitative discrepancies between the theoretical predictions and the experimental data. In this study, numerical FSI simulations of a standard flag in a viscous uniform laminar flow are performed to characterize the flow field around the flapping flag and correlate the flow field with the flag response for six Reynolds numbers (Re= 4.5 ×104, Re= 5.3 ×104, Re= 5.7 ×104, Re= 5.9 ×104, Re= 6.6 ×104, and Re= 7.5 ×104). Two-way coupled FSI simulations are conducted using commercial software ANSYS®. Rigorous solution verification is conducted first on three Re to ensure that solutions are independent of mesh and time-step refinement. Then validation is achieved by comparing the simulation predictions with experimental data. Overall, results showed a good agreement with an error range between 0.7%–4.7% for oscillation amplitude (Am), 1.3%–6.41% for drag coefficient (Cd), and 1.3%–5.3% for frequency (f). Moreover, a comparison between inviscid and viscous models is performed to evaluate the accuracy of using inviscid theoretical models for the same flow. It is observed that the inviscid model accurately predicted f but underpredicted Am and Cd, and overpredicted lift coefficient Cl. In the case of the viscous model, it is observed that a flow separation bubble and a thin flow circulation region exist on the suction side of the flag during the limit cycle oscillation (LCO). Finally, an instantaneous negative drag is observed for a short time during the LCO, suggesting that flag reconfiguration and flow separation significantly affects the drag. These observations suggest that viscous models may be needed to improve the theoretical predictions.

A Parallel Solver for FSI Problems with Fictitious Domain Approach

We present and analyze a parallel solver for the solution of fluid structure interaction problems described by a fictitious domain approach. In particular, the fluid is modeled by the non-stationary incompressible Navier–Stokes equations, while the solid evolution is represented by the elasticity equations. The parallel implementation is based on the PETSc library and the solver has been tested in terms of robustness with respect to mesh refinement and weak scalability by running simulations on a Linux cluster.

An explicit boundary condition-enforced immersed boundary-reconstructed thermal lattice Boltzmann flux solver for thermal–fluid–structure interaction problems with heat flux boundary conditions

For the thermal–fluid–structure interaction (TFSI) problems with moving boundaries, the original implicit boundary condition-enforced immersed boundary method (IBM) by Wang et al. [1] has to generate a large correlation matrix and compute its inversion at each iteration, implying that the virtual memory requirement and computational cost would grow exponentially with the number of Lagrangian points. In this work, we proposed an efficient explicit boundary condition-enforced immersed boundary method for Neumann boundary condition (NBC) to achieve high computational efficiency and maintain similar accuracy as the original implicit IBM [1], which circumvents the needs to assemble a large correlation matrix and inverse it in the original implicit IBM [1] through second-order approximation based on the error analysis using Taylor series expansion. Most importantly, the proposed explicit IBM can efficiently solve practical physics problems with a tremendous amount of Lagrangian points involving Neumann boundary condition. The comparisons of the virtual memory and computational cost between the explicit and implicit IBMs demonstrate that the explicit boundary condition-enforced IBM is not only computational efficient, but also has memory saving performance. The proposed explicit IBM integrated with the reconstructed thermal lattice Boltzmann flux solver (RTLBFS) is validated with some classical benchmarks, and the results show that the proposed explicit IBM can successfully resolve TFSI problems with Neumann boundary condition.

Fluid-structure interaction analysis of nonlinear flapping dynamic behaviors of variable stiffness composite laminated plates in viscous flows

This paper is concerned with the development of a numerical model for the analysis of nonlinear fluid–structure interaction problems of large-deformable curvilinear fiber-reinforced composite laminated plates in viscous flows. A higher-order shear deformation zig-zag theory in conjunction with nonlinear von Kármán strains is employed to accommodate the large deformations of variable stiffness composite laminated plates. An implicit partitioned fluid–structure interaction method based on an arbitrary Lagrangian-Eulerian framework is adopted for dealing with the coupling of the large-deformable plate and the viscous flow. The validity of the proposed model and method is confirmed by comparing the computed results of a two-layered plate with those available solutions in the literature. Effects of material properties and fiber paths of composite plates on the periodic limit cycle oscillation and the wake-flow vortices are examined. It is found that symmetrical lay-ups of the constant stiffness composite laminated plates can produce asymmetrical flapping shapes, resulting in asymmetrical hairpin vortex structures in the wake flow. For a variable stiffness composite laminated plate, the flexibility of the leading or trailing sections can be adjusted by the curved fiber path, which in turn leads to changes in the plate flapping shapes.

Numerical simulation of Fluid–Structure Interaction problems with viscoelastic fluids using a log-conformation reformulation

In this paper the numerical simulation of the interaction between Oldroyd-B viscoelastic fluid flows and hyperelastic solids is approached. The algorithm employed is a classical block-iterative scheme, in which the solid and the fluid mechanics problems are solved sequentially. A Galerkin finite element approach has been employed for the numerical approximation of the solid, while the flow equations are approximated using a stabilized finite element method based on the Variational Multi-Scale approach to overcome the instabilities of the Galerkin method. To be able to deal with flows with dominant elasticity, a log-conformation reformulation of the constitutive equation can be employed; here this approach is extended to Fluid–Structure Interaction problems. Several numerical examples are presented and discussed to assess the robustness of the proposed scheme and its applicability to problems with viscoelastic fluids in which elasticity is dominant interacting with hyperelastic solids.

Flow-induced vibration modeling of bluff bodies with data assimilation

Vortex-induced vibration (VIV) and galloping are two typical flow-induced vibration (FIV) problems of bluff bodies, which often cause fatigue damage or destruction of structures. Therefore, the accurate and effective FIV prediction has become a requirement of the industry in order to prevent structural damage and guide design. Although the semi-empirical model (such as the wake oscillator model) is an efficient FIV prediction tool, the precision ability of existing models is constrained due to empirical parameters and unideal mathematical equations. Generally, the numerical simulation and wind tunnel experiments are relatively accurate methods, but for complex fluid–structure interaction problems, their cost is too high. As a result, a data-driven FIV prediction model is proposed to accomplish effective and high-precision prediction in this study. The Ensemble Kalman filter (ENKF) data assimilation (DA) technique is used to combine the experimental data with a semi-empirical model. First, the sensitivity of empirical parameters is analyzed, and the most sensitive ones are selected as the target parameters for data assimilation. The mean deviation of ensemble (MDE) is proposed to represent the sensitivity of parameters. Then DA-based model is used to predict the galloping and VIV of a rectangular cylinder. The results indicate that the accuracy of the DA-based model is up to 10 times greater than that of the initial semi-empirical model. With the data-driven technology, the typical ‘quasi-steady’ theory of galloping has been improved for low Scruton number values. For the wake oscillator model, assimilating the parameters of the acceleration and velocity coupled terms can improve the prediction accuracy of VIV. Also, this modeling procedure can be regarded as a new parameter identification method from forced and free vibration.

A novel artificial neural network-based interface coupling approach for partitioned fluid–structure interaction problems

This paper presents a novel interface technique employing Artificial Neural Networks (ANN) for efficient data transfer between incompressible fluid and deformable solid domains in a partitioned fluid–structure interaction (FSI) framework. Governing differential equations (GDE) with potential flow assumptions are solved to obtain pressure values at computational nodes in the fluid domain. Pressure values are then used to train an ANN-based model to interpolate pressure loads for application at non-collocated nodes on the solid boundary. Both finite element method (FEM) and meshfree element free Galerkin (EFG) formulations are used to calculate the solid deformation. Proposed methodology is applied to solve a two-dimensional (2D) unidirectional flow problem, consisting of a flexible cantilever beam immersed in a laminar, steady, and inviscid fluid. Overwhelming mathematical intricacies of computational solvers are avoided for the sake of simplistic interface treatment, flux transfer and associated phenomena. Dedicated partitioned solvers are developed for both solid and fluid domains, which are individually benchmarked for established problems from the literature. The presented ANN-based interpolation scheme provides an alternative to higher-order polynomial algorithms at the interface boundary. The proposed scheme is simple to employ, computationally efficient, and offers competitive accuracy as well as stability.

Towards an open-source framework for Fluid–Structure Interaction using SU2, MBDyn and preCICE

Fluid–Structure Interaction (FSI) problems are a primary concern for the aerospace industry. Predicting the deformation of flexible structures due to aerodynamic forces is essential in different scenarios, e.g., for determining the performance of rotorcrafts and wind turbines. In this context, we present a new high-fidelity, open-source, modular, and user-friendly FSI simulation framework by coupling the well-established fluid solver SU2 with the multi-body structural solver MBDyn. The SU2 suite solves steady and unsteady Euler and RANS equations using a finite volume method on unstructured grids. The aerodynamic loads on the surfaces are then passed to MBDyn. Through a multi-body analysis, rotations, displacements, and the structural response of rotorcraft systems are efficiently computed and exchanged back with the fluid solver. A partitioned approach is used between the two codes, each specific for a single physical domain. Both explicit and implicit coupling were considered. The coupling is obtained through the library preCICE, which treats the two specialized solvers as “black boxes” and provides data mapping between non-matching grids. Classical FSI test cases are presented and results are compared with data from literature to validate the framework.

On aerodynamic force computation in fluid–structure interaction problems — Comparison of different approaches

This paper is interested in the numerical approximation of a two-dimensional fluid–structure interaction problem. A special attention is paid to the numerical realization of aerodynamic force (AF) calculations. Three different AF computations within finite element method framework are described and compared. First, the extrapolation of fluid stress tensor components from the interior of the fluid domain is the most straightforward method; however, this approach is of lower theoretical accuracy due to the explicit computation of velocity gradient. Second, the local reconstruction method applied on the velocity gradient is based idea of the least square fit of the gradients evaluated at finite element centroids from local patch. Third, the weak reformulation technique using the weak formulation of the fluid flow problem leads to the expression of AF in an integral form. As it avoids direct velocity gradient computation it is of higher accuracy compared to previous methods.The experimental convergence of all mentioned methods for the drag and lift coefficients is tested on the benchmark of a static cylinder in a cross-flow and further extended to the case with prescribed motion of the cylinder. Further, two FSI simulations compare the transferred energy from the fluid to the structure for the case of structure vibrations submerged in the viscous fluid and also for the flow-induced structural vibrations. The critical inlet velocity of flutter instability is determined and it is shown that for a given numerical setting the choice of AF computation can lead to the different FSI behavior.

An arbitrary Lagrangian–Eulerian method for fluid–structure interactions due to underwater explosions

Purpose This study aims to evaluate blast loads on and the response of submerged structures. Design/methodology/approach An arbitrary Lagrangian–Eulerian method is developed to model fluid–structure interaction (FSI) problems of close-in underwater explosions (UNDEX). The “fluid” part provides the loads for the structure considers air, water and high explosive materials. The spatial discretization for the fluid domain is performed with a second-order vertex-based finite volume scheme with a tangent of hyperbola interface capturing technique. The temporal discretization is based on explicit Runge–Kutta methods. The structure is described by a large-deformation Lagrangian formulation and discretized via finite elements. First, one-dimensional test cases are given to show that the numerical method is free of mesh movement effects. Thereafter, three-dimensional FSI problems of close-in UNDEX are studied. Finally, the computation of UNDEX near a ship compartment is performed. Findings The difference in the flow mechanisms between rigid targets and deforming targets is quantified and evaluated. Research limitations/implications Cavitation is modeled only approximately and may require further refinement/modeling. Practical implications The results demonstrate that the proposed numerical method is accurate, robust and versatile for practical use. Social implications Better design of naval infrastructure [such as bridges, ports, etc.]. Originality/value To the best of the authors’ knowledge, this study has been conducted for the first time.

Coupling edge-based smoothed finite element method with incompressible smoothed particle hydrodynamics for thermal fluid structure interaction problems

Numerical simulation of thermal fluid structure interaction (TFSI) problems with incompressible flows is one of the most challenging topics in computational fluid dynamics. In this paper, the recently developed edge-based smoothed finite element method (ES-FEM) is coupled with incompressible smoothed particle hydrodynamics (ISPH) for modeling TFSI problems, where the fluid domain is simulated by ISPH and the structure domain is simulated by ES-FEM method. A ghost particle based algorithm to couple the ES-FEM elements and ISPH particles is applied to implement the modeling of TFSI problems. The numerical simulation of TFSI problems using the ES-FEM-ISPH coupling method under pure Lagrangian scheme is very attractive because it can naturally handle the moving interface and free surface. The effectiveness of the ES-FEM-ISPH coupling method developed in this paper is verified by a number of numerical simulation examples with TFSI problems. From the obtained numerical results, we can conclude that the ES-FEM-ISPH coupling method is effective to simulate TFSI problems.

Semi-monolithic formulation based on a projection method for simulating fluid–structure interaction problems

Semi-monolithic formulation based on a projection method for simulating fluid–structure interaction problems

A unified and modular coupling of particle methods with fem for civil engineering problems

In this work, a modular coupling approach for particle methods with the FEM (finite element method) is presented. The proposed coupled strategy takes advantage from the ability of particle methods of dealing with large displacements and deformations, especially when solving complex fluid–structure and solid–structure interaction problems. The coupling between the FEM and particle methods is done using a co-simulation approach implemented in the open-source Kratos Multiphysics framework. The particle methods considered in this work are the DEM (discrete element method) and the PFEM (particle finite element method). The Lagrangian description of the PFEM is well suited for modeling fluids undergoing large deformations and free-surface motions, and the DEM can be used to simulate rocks, debris and other solid objects. To accelerate the convergence of the coupled strategy, a block Gauss–Seidel algorithm with Aitken relaxation is used. Several numerical examples, with an emphasis on natural hazards, are presented to test and validate the proposed coupled method.