A mimetic dual-field discretization with exact conservation properties for the incompressible Navier-Stokes equations with periodic or Dirichlet boundary conditions

The Navier-Stokes equations govern the flow of viscous fluids such as air or water. Since no general solution is known, computer simulations are used to obtain approximate solutions. As computers are unable to handle continuous representations of fields, finite-dimensional projection of fields is required, resulting in a loss of information. A...

Structural Analysis of an Offshore Jack-up Installation Vessel

Offshore installation vessels are growing in size in order that they are capable of handling the next-generation 15 and 20MW wind turbines. At the same time, it is important to gain a better understanding of their structural behaviour using the finite element (FE) method. One approach that is often used is the full vessel FE analysis, which...

Shearography non-destructive testing of thick GFRP laminates: Numerical and experimental study on defect detection with thermal loading

Thick composite materials are commonly used as load-bearing structures in marine applications. Developing a suitable and sophisticated non-destructive testing (NDT) method for thick composites is an urgent challenge to improve the safety, reliability and maintenance of these structures. Digital shearography has become an important NDT...

Effects of initial and boundary conditions on gravel-bed river morphology

Assuming that the equilibrium geometry of river channels does not depend on their initial state but solely on boundary conditions, several formulas have been derived that relate the channel depth and width to the river bankfull discharge and bed material. However, due to the existence of a threshold for sediment motion and the strong non...

Well-posedness of Hamilton–Jacobi equations in population dynamics and applications to large deviations

We prove Freidlin–Wentzell type large deviation principles for various rescaled models in populations dynamics that have immigration and possibly harvesting: birth–death processes, Galton–Watson trees, epidemic SI models, and prey–predator models. The proofs are carried out using a general analytic approach based on the well-posedness of a...

On the Bolotin's reduced beam model versus various boundary conditions

This paper is devoted to the construction of asymptotically correct simplified models of nonlinear beam equations for various boundary conditions. V.V. Bolotin mentioned that in some cases (e.g., if compressed load is near the buckling value), the so-called „nonlinear inertia“ must be taken into account. The effect of nonlinear inertia on the...

Tunable mechanical behavior of auxetic cementitious cellular composites (CCCs): Experiments and simulations

This research presents an investigation of the compressive behavior of auxetic cementitious cellular composites (CCCs) using a combination of experiments and finite element (FE) simulations. Typical auxetic centrosymmetric geometry was used as unit cells for the cellular structure and fiber reinforced cementitious mortar were used as...

Influence of various boundary conditions on local buckling of steel tubular piles: Effects of restraints, imperfections and residual stresses

The main focus of this thesis is the influence of different real boundary conditions on the failure mechanism of local buckling of steel tubular piles. The research was started with the theoretical method of describing boundary condition by specifying the degrees of freedom per boundary condition. The method makes use of the radial, meridional...

Implementation of non-trivial boundary conditions in MPM for geotechnical applications

This paper describes current work on the implementation of non-trivial boundary conditions (BCs) for improving the general applicability of the Material Point Method (MPM) to geotechnical boundary values problems. It summarises novel boundary treatments (non-trivial BCs) in MPM for (i) flow conditions, as well as (ii) the application of a...

An idealized description for the diurnal cycle of the dry atmospheric boundary layer

We present a conceptual model for the diurnal cycle of the dry atmospheric boundary layer (ABL). It may serve as a framework for future numerical studies on the transitional dynamics that characterize the ABL over land. The conceptual model enables us to define expressions for relevant physical scales as a function of the most prominent...

Effect Of Mechanical Input Energy On Piezoelectric Energy Harvesting

Piezoelectric energy harvesting technology is an alternative source for powering low power electronics. The ability of piezoelectric materials to convert ambient vibrational energy into usable electrical energy is seen as a promising battery-free solution to be used in inhospitable areas to self-power electronics for a longer time with little...

Parameters for the collapse of turbulence in the stratified plane Couette flow

We perform direct numerical simulation of the Couette flow as a model for the stable boundary layer. The flow evolution is investigated for combinations of the (bulk) Reynolds number and the imposed surface buoyancy flux. First, we establish what the similarities and differences are between applying a fixed buoyancy difference (Dirichlet) and...

Pipeline integrity: Assessment for dynamic compressive loading of 18"ILT installation

An enhanced methodology is proposed to include both the loading and the resistance of the upper stem (pipeline) in 18" ILT installation. Loading behavior and buckling capacity have been investigated. The upper stem behaves quasi-statically for all HMC projects, this corresponds to the current method of applying maximum found loads statically....

Higher order exponential splittings for the fast Non-linear Fourier Transform of the Korteweg-De Vries equation

Non-linear Fourier Transforms (NFTs) enable the analysis of signals governed by certain non-linear evolution equations in a way that is analogous to how the conventional Fourier transform is used to analyse linear wave equations. Recently, fast numerical algorithms have been derived for the numerical computation of certain NFTs. In this paper,...

Development and implementation of moving boundary conditions in the Material Point Method

A new technique is developed in this thesis, which applies boundary conditions to moving boundaries in the Material Point Method (MPM). While MPM has been proven to be useful in slope stability, foundation and seabed ploughing modelling, the application of boundary conditions is still a challenge,<br/>because the location of the boundary is...

Diffusion in a polymeric environment

Cells of the most common organisms like plants and animals are filled with polymeric networks that fulfil important functions of the cell. There is however no analytically solvable model that describes diffusion in such a cell. This thesis presents a model for diffusion in polymeric environments, and some predictions about the behaviour of the...