Papers by Keyword: Fluid-Structure Interaction

Abstract: The present work proposes the development of numerical tools for solving fluid-structure interaction (FSI) problems where the structure is coupled with cables. For the numerical treatment of fluids in incompressible flow, the Navier-Stokes and continuity equations are discretized using a semi-implicit version of the characteristic-based split (CBS) method in the context of the finite element method (FEM), where linear tetrahedral elements are used. In the presence of moving structures, the flow equations are described through an arbitrary Lagrangian-Eulerian (ALE) formulation and a numerical scheme of mesh movement is adopted. The structure is treated through a three-dimensional rigid body approach and the cable through an elastic model with geometric nonlinearity and spatial discretization by the nodal position finite element method (NPFEM). The system of equations of motion can be temporally discretized using the implicit Newmark and generalized-α methods and a partitioned coupling scheme is used taking into account fluid-structure and cable-structure couplings. The algorithms proposed here are verified using numerical applications.

Abstract: The analysis of the hydro-elastic interactions of the covering membrane of fluid-filled cavities or containers has a main importance due to the solution of practical problems founded in engineering applications. In this paper the dynamic behaviour of the bottom membrane of a rectangular container filled with a non-viscous and incompressible fluid is analyzed. The fluid velocity potential is obtained first by applying a method of separation of variables and afterwards the pressure field is calculated with the momentum’s linearized equation. Taking into account the deformation equation for the membrane in contact with the fluid and by applying a discretization procedure to the associated generalized work equation, a system is obtained, for the calculus of the membrane frequencies of vibration. The influence of different geometrical parameters such as dimension, aspect ratio, container relative height, relative thickness as well as the fluid density on these frequencies is analysed. Validation of the method is made by comparing the results with those obtained by other authors and theories.

Abstract: To add reliability to numerical simulations, Uncertainty Quantification is considered to be a crucial tool for clinical decision making. This especially holds for risk assessment of cardiovascular surgery, for which threshold parameters computed by numerical simulations are currently being discussed. A corresponding biomechanical model includes blood flow, soft tissue deformation, as well as fluid-structure coupling. Thereby, structural material parameters have a strong impact on the dynamic behavior. In practice, however, particularly the value of the Young's modulus is rarely known in a precise way, and therefore, it reflects a natural level of uncertainty. In this work we introduce a stochastic model for representing variations in the Young's modulus and quantify its effect on the wall sheer stress and von Mises stress by means of the Polynomial Chaos method. We demonstrate the use of uncertainty quantification in this context and provide numerical results based on an aortic phantom benchmark model.

Abstract: The need for improvements in engineering designs especially for coupled structures is nowadays becoming a major industry request. Today there is a desire to perform optimizations in order to receive optimal system properties. However, for computationally expensive simulation models, an optimization may be too tedious to be motivated. Deterministic approaches are unable to take into account all the variability’s that characterize design input properties without leading to oversized structures. The objectives of this work are to quantify the influence of material and operational uncertainties on the performance of structures coupled with fluid, and to develop a reliability-based design and optimization methodology for this type of the structures. Such a problem requires a very high computation cost, which is mainly due to the calculation of gradients, especially when a finite element model is used. To simplify the optimization problem and to find at least a local optimum solution, a new method based on semi-numerical solution is proposed in this paper. The results demonstrate the viability of the proposed reliability-based design and optimization methodology relative to the classical methods, and demonstrate that a probabilistic approach is more appropriate than a deterministic approach for the design and optimization of structures coupled with fluid