Andreas Zilian

Numerical Modeling of Flow-Driven Piezoelectric Energy Harvesting Devices

The present work proposes uniform and simultaneous computational analysis of smart, low power energy harvesting devices targeting flow-induced vibrations in order to enable reliable sensitivity, robustness and efficiency studies of the associated nonlinear system involving fluid, structure, piezo-ceramics and electric circuit. The article introduces a monolithic approach that provides simultaneous modeling and analysis of the coupled energy harvester, which involves surface-coupled fluid-structure interaction, volume-coupled piezoelectric mechanics and a controlling energy harvesting circuit for applications in energy harvesting. A space-time finite element approximation is used for the numerical solution of the governing equations of the flow-driven piezoelectric energy harvesting device. This method enables modeling of different types of structures (plate, shells) with varying cross sections and material compositions, and different types of simple and advanced harvesting circuits.

Enriched space-time finite elements for fluid-structure interaction

This paper presents a new numerical approach to deal with fluid structure interaction problems where a thin structure is immersed in an incompressible fluid. Spacetime finite elements are used to discretized the equations using a discontinuous time scheme. In order to take into account the discontinuities due to the structure in the fluid domain, the approximation fluid fields are enriched with appropriate discontinuous functions through a partition of unity (XFEM). The method allows incompatible meshes between fluid and structure, the structure mesh can move freely in the fluid fixed Eulerian mesh.

Modelling of Fluid-Structure Interaction – Effects of Added Mass, Damping and Stiffness

Fluid-flow around mechanical structures can sometimes lead to catastrophic failures. Improved modelling of fluid/structure interaction is required for safety and mechanical considerations. In this contribution, concepts for modelling the interaction of structures and fluids are presented. Starting from excitation mechanisms and associated classifications, various model depth approaches are compared. Among them, the use of added coefficients for quasisteady problems is discussed. On the basis of potential flow theory, different approaches for determining fluid-induced additional mass are established and illustrated using an analytical example. Given the limitations of simplifying the engineering models, the second part of the paper provides a brief overview on computational methods for fluid-structure interaction and presents a monolithic modelling approach using space-time finite elements for discretisation of both fluid and structure. Applications from aero- and hydro-elasticity show the applicability of computational methods for problems involving flow-induced added mass, damping, and stiffness.

Meshfree collocation method for implicit time integration of ODEs

An implicit time integration meshfree collocation method for solving linear and nonlinear ordinary differential equations (ODEs) based on interpolating moving least squares technique, which uses singular weights for constructing ansatz functions, is presented. On an example of a system of equations for Foucault pendulum, the flexibility of the proposed approach is shown and the accuracy, convergence, and stability properties are investigated. In a nonlinear case, the method gives accurate results, which is demonstrated by the solution of Lorenz equations. The typical trajectory patterns, e.g. butterfly pattern, were observed and the properties of the method are compared to those of a higher-order time integration method.