Morphodynamic equilibria in double–inlet systems: Their existence, multiplicity and stability

Tidal inlet systems, which consist of back–barrier basins connected to the open sea by one or multiple inlets, are found at many places along sandy coasts. They are valuable for ecology (breeding and feeding areas), economy (gas–mining and sand–mining) and recreation, and are important for coastal safety. But they are also sensitive to external...

Morphodynamic Equilibria in Double-Inlet Systems

Tidal basins are connected to the outer sea by one or more tidal inlets. In this presentation, we focus on so-called double inlet systems, i.e., tidal inlet systems with two connecting channels. A typical example is the Marsdiep-Vlie system, located in the Dutch Wadden Sea. Using an idealized morphodynamic model, we aim at directly finding...

Initial formation of channel–shoal patterns in double–inlet systems

Channel–shoal patterns are often observed in the back–barrier basins of inlet systems and are important from both an economical and ecological point of view. Focussing on double–inlet systems, the initial formation of these patterns is investigated using an idealized model. The model is governed by the depth–averaged shallow water equations,...

Comparisons between beam and continuum models for modelling wheel-rail impact at a singular rail surface defect

A singular rail or wheel surface irregularity, such as a squat, insulation joint or wheel flat, can cause large wheelrail impact force. Both the magnitude and frequency content of the impact force need to be correctly modelledbecause they are closely related to the formation, deterioration and detection of such irregularities. In this paper,we...

Morphodynamic Equilibria in Double-Inlet Systems: Existence and Stability

The existence of morphodynamic equilibria of double-inlet systems is investigated using a cross-sectionally averaged morphodynamic model. The number of possible equilibria and their stability strongly depend on the forcing conditions and geometry considered. This is illustrated by considering a rectangular double-inlet system forced by M<sub...

Finite Element Solution of Rolling Contact and Analysis of Squats Formation

One goal of this thesis is to study the performance and accuracy of an explicit finite element (FE) method for frictional rolling contact in a wider-range of conditions. The other goal is to reveal the physical phenomena of squats and the mechanisms behind, such as cracking mechanisms and development process. The first part studies the...

Numerical modeling of dynamic frictional rolling contact with an explicit finite element method

The modeling of dynamic frictional rolling contact is crucial for accurately predicting behavior and deterioration of structures under dynamic interactions such as wheel/rail, tire/road, bearings and gears. However, reliable modeling of dynamic frictional rolling contact is challenging, because it requires a careful treatment of friction and...

Pre-cracking development of weld-induced squats due to plastic deformation: Five-year field monitoring and numerical analysis

Weld-induced squats are a major damage type in high-speed railways as well as in conventional railways. They incur high maintenance costs and endanger operational safety. This paper first presents and analyzes five-year continual field monitoring observations and measurements of squats at rail welds. A hypothesis of the formation and development...

Investigation of the formation of corrugation-induced rail squats based on extensive field monitoring

Rail squats originate from a number of sources, such as corrugations, indentations and welds. A five-year continual field monitoring study was performed on squats induced by corrugations. This study indicated that a small black depression formed at the corrugation under wheel-rail dynamic forces, and then, a primary crack typically initiated...

Applicability of half-space-based methods to non-conforming elastic normal contact problems

The half-space assumption has been employed in many solution methods for non-conforming contact problems in elasticity such as the Hertz theory and the Kalker's variational theory. It is generally believed that to guarantee acceptable accuracy in these half-space-based methods, the characteristic size (twice length of one semi-axis) of the...

Interconnecting Urban Planning with Multi-Scale Urban Quality: Review of Macro Scale Urban Redevelopment Project on Micro Scale Urban Quality in Shenzhen

The Shenzhen planning system has been effective in promoting economic growth through the prodigious urbanization of land. It has given priority to the ‘macro-level’ planning goals of economic growth through physical development. Questions can be raised about the physical and social outcomes from the development process at the ‘micro-level’, not...

Residual fatigue life evaluation of rail at squats seeds using 3D explicit finite element analysis

A modeling procedure to predict the residual fatigue life of rail at squats seeds is developed in this article. Two models are involved: a 3D explicit Finite Element (FE) model to compute the stress and strain at squats in rail, and the J-S fatigue damage model to determine the residual fatigue life on the basis of the computed stress and strain...

Influences of characteristic size of contact bodies on rolling contact

The rolling contact of elastic bodies (upper body and lower body) can be analyzed with the Hertz theory and the Kalker’s model. It is generally believed that the width of the contact area should be much smaller than the characteristic size of each elastic body, to ensure that the half-space assumption is valid. However the definition of “much...

Improvement on bacteria-induced calcium mineralization ability of Bacillus pseudofirmus by an integrated high-throughput screening strategy

The CaCO3-mineralizing bacteria from different taxonomic groups have shown potential in restoration of construction material such as concretes, cements and stony materials. However, these strains are far from the demand of practical application due to some shortages, including the low mineralizing capacity. In this work, an integrated high...

Improvement on bacteria-induced calcium mineralization ability of Bacillus pseudofirmus by an integrated high-throughput screening strategy

The CaCO3-mineralizing bacteria from different taxonomic groups have shown potential in restoration of construction material such as concretes, cements and stony materials. However, these strains are far from the demand of practical application due to some shortages, including the low mineralizing capacity. In this work, an integrated high...