Numerical analysis of train-track-subgrade dynamic performance with crumb rubber in ballast layer

Crumb rubber (CR) has been proposed to apply in the ballast or sub-ballast layer for ballast degradation mitigation and vibration (noise) reduction. The CR can change the ballast layer stiffness, which can affect the train-track-subgrade dynamic performance and cause travel comfort and safety issues. Towards this, this study aims at...

Analysis of Railway Ballasted Track Stiffness and Behavior with a Hybrid Discrete-Continuum Approach

Railway ballasted track stiffness is an important indicator to identify supporting condition that ensures that the facility is well designed and functioned. Although many studies have been performed on track stiffness based on experimental tests and finite-element methods, the factors influencing the track stiffness have not been completely...

Advanced and Accurate Discretization Schemes for Relevant PDEs in Finance

This thesis studies advanced and accurate discretization schemes for relevant partial differential equations (PDEs) in finance. We start with techniques which may be particularly useful for the pricing of so-called vanilla financial options, European or American, and then move on to more complex models for the pricing of exotic options.<br/>

Accuracy aspects of conventional discretization methods for scalar transport with nonzero divergence velocity field arising from the energy balance equation

We are concerned with the numerical solution of a linear transport problem with nonzero divergence velocity field that originates from the spectral energy balance equation describing the evolution of wind waves and swells in coastal seas. The discretization error of the commonly used first-order upwind finite difference and first-order vertex...

Coupled discrete-continuum approach for railway ballast track and subgrade macro-meso analysis

This paper presents a multi-layer railway ballast track and substructure model, where a coupled discrete and continuous method is used for macro-meso dynamic behaviour analysis under moving wheel loads. In this coupled model, the discrete element method (DEM) is utilised to build the superstructure of the ballast track (i.e. rail, fastener,...

Macro-meso dynamic analysis of railway transition zone: Hybrid DEM/FDM simulation and experimental validation

To probe into the mechanical behaviour of railway transition zone from the macro-meso aspects, a numerical model of transition zone is built that hybrids the Discrete Element Method (DEM) and Finite Difference Method (FDM). The DEM is utilised to simulate the ballast bed and sleeper, because it can consider the realistic ballast shapes and...

A dual interface method in cylindrical coordinates for two-phase pipe flows

This research entails the numerical simulation of physical flow instabilities that can occur in two-phase pipe flows with a new efficient algorithm. The fluids are assumed to be immiscible, and the flow is incompressible and isothermal in a straight circular pipe section with a certain inclination. The numerical algorithm that was developed...

Effects of Soil Spatial Variability on Bearing Capacity of Shallow Foundations

This paper studies the effect of soil spatial variability on bearing capacity of shallow foundations. The stochastic soil property is the undrained shear strength considered as a non-Gaussian random variable. The random variable is simulated using Local Average Subdivision Method. A Monte Carlo simulation approach is followed in combination with...

Application of the finite-difference contrast-source inversion algorithm to seismic full-waveform data

We have applied the finite-difference contrast-source inversion (FDCSI) method to seismic full-waveform inversion problems. The FDCSI method is an iterative nonlinear inversion algorithm. However, unlike the nonlinear conjugate gradient method and the Gauss-Newton method, FDCSI does not solve any full forward problem explicitly in each iterative...

Near-surface attenuation estimation using wave-propagation modeling

The effect of the near surface on seismic land data can be so severe that static corrections are insufficient. Full-waveform inversion followed by redatuming may be an alternative, but inversion will work only if the starting model is sufficiently close to the true model. As a first step toward determining a viscoelastic near-surface model, we...

Application of a linear finite-frequency theory to time-lapse crosswell tomography in ultrasonic and numerical experiments

Time-lapse seismic monitoring is the geophysical discipline whereby multiple data sets recorded at the same location but at different times are used to locate and quantify temporal changes in the elastic parameters of the subsurface. We validate a time-lapse monitoring method by crosswell tomography using two types of wavefield-modeling...

Coupled fluid-flow and magnetic-field simulation of the Riga dynamo experiment

Magnetic fields of planets, stars, and galaxies result from self-excitation in moving electroconducting fluids, also known as the dynamo effect. This phenomenon was recently experimentally confirmed in the Riga dynamo experiment [ A. Gailitis et al., Phys. Rev. Lett. 84, 4365 (2000) ; A. Gailitis et al., Physics of Plasmas 11, 2838 (2004) ],...

Validation of first-order diffraction theory for the traveltimes and amplitudes of propagating waves

Ultrasonic measurements of acoustic wavefields scattered by single spheres placed in a homogenous background medium (water) are presented. The dimensions of the spheres are comparable to the wavelength and the wavelength and represent both positive (rubber) and negative (teflon) velocity anomalies with respect to the background medium. The...

The Physalis method for particle simulations

This paper illustrates the Physalis method designed for the simulation of Navier-Stokes flows with suspended rigid spheres. The method exploits the no-slip condition to linearize the flow about a rigid body motion in the immediate vicinity of each particle. In this way an analytic solution valid within a mesh length near the particle surface...

Design techniques for thermal management in switch mode converters

Tweedimensionaal onderzoek turbulente diffusiekoëfficiënten