A sharp interface Lagrangian-Eulerian method for rigid-body fluid-structure interaction

SummaryThe fractional step method (FSM) is an efficient solution technique for the particle finite element method, a Lagrangian‐based approach to simulate fluid–structure interaction (FSI). Despite various refinements, the applicability of the FSM has been limited to low viscosity flow and FSI simulations with a small number of equations along the fluid–structure interface. To overcome these limitations, while incorporating nonlinear response in the structural domain, an FSM that unifies structural and fluid response in the discrete governing equations is developed using the quasi‐incompressible formulation. With this approach, fluid and structural particles do not need to be treated separately, and both domains are unified in the same system of equations. Thus, the equations along the fluid–structure interface do not need to be segregated from the fluid and structural domains. Numerical examples compare the unified FSM with the non‐unified FSM and show that the computational cost of the proposed method overcomes the slow convergence of the non‐unified FSM for high values of viscosity. As opposed to the non‐unified FSM, the number of iterations required for convergence with the unified FSM becomes independent of viscosity and time step, and the simulation run time does not depend on the size of the FSI interface. Copyright © 2016 John Wiley & Sons, Ltd.

We present a fluid---structure interaction (FSI) modeling method based on using the deforming-spatial-domain/stabilized space---time (DSD/SST) method for the fluid mechanics part and a finite difference (FD) method for the structural mechanics part. As the structural mechanics model, we focus on the thin-shell model. The fluid mechanics equations with moving boundaries are solved with the DSD/SST method and the thin-shell structural mechanics equation is solved with a FD method, with partitioned coupling between the two parts. The coupling of the DSD/SST and FD solvers makes sure that the boundary conditions on the fluid-structure interface at the end of each time step are matched between the fluid and the structure. A hanging plate in vacuum under gravitational force is performed to validate the structure solver. In addition, a pitching plate in a uniform flow is simulated to validate the FSI solver. The present results are in reasonable agreement with data predicted by other methods.

In this thesis, a strategy to model the behavior of fluids and their interaction with deformable bodies is proposed. The fluid domain is modeled by using the lattice Boltzmann method, thus analyzing the fluid dynamics by a mesoscopic point of view. It has been proved that the solution provided by this method is equivalent to solve the Navier-Stokes equations for an incompressible flow with a second-order accuracy. Slender elastic structures idealized through beam finite elements are used. Large displacements are accounted for by using the corotational formulation. Structural dynamics is computed by using the Time Discontinuous Galerkin method. Therefore, two different solution procedures are used, one for the fluid domain and the other for the structural part, respectively. These two solvers need to communicate and to transfer each other several information, i.e. stresses, velocities, displacements. In order to guarantee a continuous, effective, and mutual exchange of information, a coupling strategy, consisting of three different algorithms, has been developed and numerically tested. In particular, the effectiveness of the three algorithms is shown in terms of interface energy artificially produced by the approximate fulfilling of compatibility and equilibrium conditions at the fluid-structure interface. The proposed coupled approach is used in order to solve different fluid-structure interaction problems, i.e. cantilever beams immersed in a viscous fluid, the impact of the hull of the ship on the marine free-surface, blood flow in a deformable vessels, and even flapping wings simulating the take-off of a butterfly. The good results achieved in each application highlight the effectiveness of the proposed methodology and of the C++ developed software to successfully approach several two-dimensional fluid-structure interaction problems.

Investigation on the delayed closure of the suction valve in the refrigerator compressor by FSI modeling

This work presents a direct time domain methodology for Fluid-Structure Interaction analysis between linearized fluids and rigid bodies. To this end, a direct time domain Boundary Element formulation pertaining to 3-D wave propagation in acoustic media is developed. The method is based on higher order B-Spline fundamental solutions developed for scalar wave propagation in 3-D infinite media and uses higher order spatial discretization. Integration of singularities appearing in the fundamental solutions is treated numerically through triangle coordinates and a successive mapping technique. This method is used within the B-Spline Impulse Response framework for the calculation of the time history of the response of the acoustic medium and the calculation of the hydrodynamic forces on the wetted surface of the fluid-structure interface. The proposed B-Spline BEM is stable as compared to the relevant Retarded Potential formulations reported in the literature. Although this method is non-local in time, only a relatively small number of time steps are required in the B-Spline Response functions, making the method very efficient especially for prolonged external excitations. Fluid-Structure interaction models are proposed for the dynamics of rigid bodies submerged in, or floating on, semi-infinite fluid domains. Validation of the BEM is presented in the application examples. The accuracy stability and efficiency of the proposed models are also demonstrated.

A novel coupled Riemann SPH–RKPM model for the simulation of weakly compressible fluid–structure interaction problems

Numerically stable fluid–structure interactions between compressible flow and solid structures

3D MRI-based multicomponent thin layer structure only plaque models for atherosclerotic plaques

A CFD-FEM based partitioned fluid structure interaction model to investigate surface cracks in elastohydrodynamic lubricated line contacts

An efficient partitioned framework to couple Arbitrary Lagrangian-Eulerian and meshless vector form intrinsic finite element methods for fluid-structure interaction problems with deformable structures

An interface and geometry preserving phase-field method for fully Eulerian fluid-structure interaction

The high performance of nature’s creations and biological assemblies has inspired the development of engineered counter parts that may outperform or provide new capabilities to conventional systems. In particular, the wings of bats contain distributed arrays of micro-scaled flow sensitive hair receptors over their surface, which inspires artificial hair sensors (AHS) development in aerodynamic feedback control designs using the micro-electro-mechanical systems (MEMS). One approach investigates the possibility of installing AHS on the leading edges of the wings of small-scaled unmanned aerial vehicles (UAVs) to improve the aerodynamic control. Our major motivation for the present study is that current mathematical models have limited relevance to aerodynamic situations because they are analyzed in steady or purely oscillatory flows. Our overall objective is to understand AHS fluid-structure interaction (FSI) in flow regimes relevant to small-scaled UAVs, for which we speculate a steady baseline flow perturbed by an oscillatory component is an appropriate flow reference condition. Towards understanding the AHS in this situation, we investigate the dynamic response of a hair receptor in a creeping flow environment with a steady and oscillatory component. We present time varying deflection and bending moment of the artificial hair sensors at different freestream velocities. For this, a three-dimensional FSI model is developed for the flexible hair-structure in the airflow, which is coupled with a finite element model using the computational fluid dynamics (CFD). The Navier-Stokes equations including continuity equation are solved numerically for the CFD model. To describe the dynamic response of the hair receptors, the natural frequencies and mode shapes of the hair receptors, computed from the FSI model, are compared with the excitation frequencies of the surrounding airflow. This model also describes both the boundary layer effects and effects of inertial forces due to FSI of the hair receptors. For supporting the FSI model, the dynamic response of the hair receptor is also validated considering the Euler-Bernoulli beam theory including the steady and unsteady airflow.

According to ANSYS - developer of the Multiphysics platform for computer simulations - the FSI (Fluid-Structure Interaction) model can be used in all cases where a fluid encounters a solid structure, for example, wind gusts rotating a turbine, air washing the surface of a moving car etc. This method finds applications especially in the aeronautical and automotive industries, but also in medical research, such computer simulations track the influences of blood pressure and blood flow velocity in the veins. This paper deals with an extension of applying this method in a lesser field, namely in investigating gas explosion events through computer simulations. For this, in the virtual domain, a geometry similar to a house was built, in which an explosive atmosphere generated by an accidental natural gas leak was simulated. Following the source of initiation, the process of rapid combustion of combustible gas takes place, the dynamic effects produced by the pressures generated by the expansion of the gases being calculated and quantified by the FSI model. The results obtained by applying this method in the simulations help in the decision-making process to adopt the most effective measures to prevent explosion-type events of air-fuel mixtures, being useful in the development of explosion risk assessment studies, for identifying the worst-case scenario.

Intervention treatments for aortic stenosis strongly rely on the use of a medical balloon catheter which is utilized for dilating the narrowed aortic valve or the deployment of the implanted devices. However, the complete inflation of the balloon will block the blood outflow and cause instability. This paper demonstrates a computational analysis method to examine the influence of the amount of balloon inflation volume on balloon movement within a pulsating fluid environment. A tri-folded typical shape of the balloon model was inflated by pressurization. The balloon’s front projection area changes during both simulation and experiment were recorded. To address the interaction between the balloon model with varying inflation levels and the introduction of fluid into the arched aorta, a Fluid-Structure Interaction (FSI) model was developed. Compared with the experimental data, the front projection area in the simulation showed a similar increment, which can be used to validate the balloon model. For FSI simulation, the balloon catheter’s maximum displacement rises with the inflation level, with a slight rise at about 10 ml and a substantial rise at 20 ml volume. This work showed a significant advancement in the ability to replicate balloon movement during valvuloplasty using an FSI model.

FSI-simulation of ductile fracture propagation and arrest in pipelines: Comparison with existing data of full-scale burst tests