Fluid-structure interaction models

To obtain fracture properties of HDPE conventional essential work of ifacture tests are performed. Two grades of blow-moulded HDPE are tested at different test speeds. The main aim of these tests is to estimate traction-separation (cohesive zone) properties of the materials. In future work, these will be combined with the fluid-structure interaction model to provide a powerful tool for predicting the complex behaviour and potential failure of fluid-filled containers imder drop impact. 

Computational fluid dynamics models were developed over the years that include the effects of leaflet motion and its interaction with the flowing blood (Bellhouse et al., 1973 Mazumdar, 1992). Several finite-element structural models for heart valves were also developed in which issues such as material and geometric nonlinearities, leaflet structural dynamics, stent deformation, and leaflet coaptation for closed valve configurations were effectively dealt with (Bluestein and Einav, 1993 1994). More recently, fluid-structure interaction models, based on the immersed boundary technique. 

Sonntag SJ, Kanfmann TA, Biisen MR, Laumen M, Linde T, Schmitz-Rode T, et al. Simulation of a pulsatile total artificial heart development of a partitioned fluid structure interaction model. J Fluids Struct 2013 38 187-204. 

Three-Dimensional Fluid-Structure Interaction Modeling of Expiratory Flow... 

Purely electrical models of the heart are only a start. Combined electromechanical finite-element models of the heart take into account the close relationship that exists between the electrical and mechanical properties of individual heart cells. The mechanical operation of the heart is also influenced by the fluid-structure interactions between the blood and the blood vessels, heart walls, and valves. All of these interactions would need to be included in a complete description of heart contraction. 

This problem falls into a category of strongly coupled fluid-structure interaction (FSI) problems due to comparable stiffnesses of the container and its liquid content. Hence, accurate prediction of containers behaviour requires a liquid-container interaction model. Here, a two-system FSI model based on the Finite Volume Method is employed, and a good agreement is found between measured and predicted pressure and strain histories. 

This paper presents the combined experimental/numerical investigation of the behaviour of fluid-filled plastic containers subjected to drop impact. Drop Impact experiments were conducted on original and modified bottles. During the test, strain and pressure histories were recorded at various positions. Tests were simulated numerically using the two-system FSI model. Both solid and fluid domains remain fixed during the calculations, i.e. a small-strain analysis was performed for the solid while an Eulerian fi-ame of reference was used for the fluid. This procedure was found to be simple, stable and efficient. Numerical results agreed well with experimental data, demonstrating the capability of the code to cope with this complex fluid-structure interaction problem. 

Pulsatile flow in an elastic vessel is very complex, since the tube is able to undergo local deformations in both longitudinal and circumferential directions. The unsteady component of the pulsatile flow is assumed to be induced by propagation of small waves in a pressurized elastic tube. The mathematical approach is based on the classical model for the fluid-structure interaction problem, which describes the dynamic equilibrium between the fluid and the tube thin wall (Womersley, 1955b Atabek and Lew, 1966). The dynamic equilibrium is expressed by the hydrodynamic equations (Navier-Stokes) for the incompressible fluid flow and the equations of motion for the wall of an elastic tube, which are coupled together by the boundary conditions at the fluid-wall interface. The motion of the liquid is described in a fixed laboratory coordinate system (f , 6, f), and the dynamic... 

Afterwards an update to the mesh deformation module is presented, which enables to represent the exact deflections for every CFD surface grid node, which are delivered by the coupling matrix. Performance limitations do not allow to use all points as input for the basic radial-basis-function based mesh deformation method. Then the FSI-loop to compute the static elastic equilibrium is described and the application to an industrial model is presented. Finally, a strategy how to couple and deflect control smfaces is shown. Therefore, a possible gapless representation by means of different coupling domains and a chimera-mesh representation is shown. This section describes the bricks, which are combined to a fluid-structure interaction loop. Most of the tools are part of the FlowSimulator software environment (Fig. 20.11). 

M. H. Kim and W. C. Koo, 2D fuUy nonhnear numerical wave tanks, Numerical Modeling in Fluid-Structure Interaction, ed. S. K. Chakrabarti (WIT Press, Great Britain, 2005), Chap. 2. 

In recent years, the SPH methods in particular have gone through major improvements and their application was expanded into a wider range of engineering problems. These include both more advanced physical models and more advanced engineering processes. For example, SPH was successfully used to simulate non-Newtonian fluid flows and viscoelastic materials. It has been also used for the analysis of fluid-structure interaction problems, fluid flow in porous media and fractures, heat transfer and reacting flow problems. 

Brown, T. D., M. Bottlang, D. R. Pedersen, and A. J. Banes. 2000. Development and experimental validation of a fluid/structure-interaction finite element model of a vacuum-driven cell culture mechanostimulus system. Comput Methods Biomech Biomed Engin 3 65-78. 

In order to account for boundary deformation in the fluid mesh, the fluid governing equations are recast in an Arbitrary Lagrangian-Eulerian (ALE) description in CFX, where the fluid mesh deformation and velocity are solved based on a Lapladan diffusion model. The fluid-structure interaction is achieved by matching the forces and velocities at the common interface between the fluid and structure, via... 

Future work incorporating unsteady inhalation and expiration cycle is intended, to look at the full breathing effect on the tongue dynamics. Ultimately, a realistic pharyngeal airway model is also intended to be used for further fluid-structure interaction investigation. 

In the same vein, otic could pose several other questions pertaining to uncertainty propagatiOTi, system identification, vibratiOTi energy flow modeling, and treatment of multiphysics problems (such as fluid-structure interactions, soil-structure interactions, primary-secondary structure interactions, etc.). The discussion in the following sections will focus on a few of these issues. 

While fluid-structure interactions clearly create damaging mechanical stresses, surfactant physicochemical interactions are critical to the protection of the airway epithelium. In order to investigate this important interaction during airway reopening, it is necessary to expand the models above by introducing the biophysical properties of surfactant located in the hning fluid. This includes surfactant transport in the bulk phase by convection and diffusion, and the sorption kinetics between the bulk phase and the air-liquid interface. The flow fields in the bulk fluid and sorption kinetics at the interface both contribute to the rate and manner in which surfactant adsorbs to the interface where it locally decreases surface tension. These interactions are depicted in Figure 16.8, and defined below by Equations 16.10 and 16.11. 

The singlet-level theories have also been applied to more sophisticated models of the fluid-solid interactions. In particular, the structure of associating fluids near partially permeable surfaces has been studied in Ref. 70. On the other hand, extensive studies of adsorption of associating fluids in a slit-like [71-74] and in spherical pores [75], as well as on the surface of spherical colloidal particles [29], have been undertaken. We proceed with the application of the theory to more sophisticated impermeable surfaces, such as those of crystalline solids. 

Let us consider a simple model of a quenched-annealed system which consists of particles belonging to two species species 0 is quenched (matrix) and species 1 is annealed, i.e., the particles are allowed to equlibrate between themselves in the presence of 0 particles. We assume that the subsystem composed of 0 particles has been a usual fluid before quenching. One can characterize it either by the density or by the value of the chemical potential The interparticle interaction Woo(r) does not need to be specified for the moment. It is just assumed that the fluid with interaction woo(r) has reached an equlibrium at certain temperature Tq, and then the fluid has been quenched at this temperature without structural relaxation. Thus, the distribution of species 0 is any one from a set of equihbrium configurations corresponding to canonical or grand canonical ensemble. We denote the interactions between annealed particles by Un r), and the cross fluid-matrix interactions by Wio(r). 

One possibility for this was demonstrated in Chapter 3. If impact theory is still valid in a moderately dense fluid where non-model stochastic perturbation theory has been already found applicable, then evidently the continuation of the theory to liquid densities is justified. This simplest opportunity of unified description of nitrogen isotropic Q-branch from rarefied gas to liquid is validated due to the small enough frequency scale of rotation-vibration interaction. The frequency scales corresponding to IR and anisotropic Raman spectra are much larger. So the common applicability region for perturbation and impact theories hardly exists. The analysis of numerous experimental data proves that in simple (non-associated) systems there are three different scenarios of linear rotator spectral transformation. The IR spectrum in rarefied gas is a P-R doublet with either resolved or unresolved rotational structure. In the process of condensation the following may happen. 

Bridging the gap between micro- and macro-scale is the central theme of the first contribution. The authors show how a so-called Energy-Minimization Multi-Scale (EMMS) model allows to do this for circulating fluid beds. This variational type of Computational Fluid Dynamics (CFD) modeling allows for the resolution of meso-scale structures, that is, those accounting for the particle interactions, and enables almost grid-independent solution of the gas-solids two-phase flow. 

As an example we consider the flow of a fluid/adsorbate mixture through the big pores of a skeleton, thought like an elastic solid with an ellipsoidal microstructure, and propose suitable constitutive equations to study the coupling of adsorption and diffusion under isothermal conditions in particular, we insert the concentration of adsorbate and its gradient in the usual variables, other than microstructural ones. Finally, the expression of the dissipation shows clearly its dependence on the adsorption and the diffusion, other than on the micro-structural interactions. The model was already applied by G. and Palumbo [7] to describe the transport of pollutants with rainwater in soil. 

First, a complete description of the adsorbent is required this must include details of its solid structure, surface chemical structure, pore size and shape. One starts by assuming that the pores in the model adsorbent are all of the same size and shape and that they are unconnected. Secondly, the nature of the fluid-fluid and fluid-solid interactions must be precisely defined since the validity of the calculations is dependent on the accuracy of the intermolecular potential functions. 

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