Computational modelling of waves in harbours using ray methods

This thesis is concerned with the development of a new computational model for the prediction of wind-generated waves in harbours using a new type of ray tracing technique. The thesis includes a background to the study, an exposition of the theory of the new ray tracing technique, a description of the computational techniques adopted, a new method for interpreting ray diagrams, comparisons with analytical solutions, alternative numerical models and a physical model, and finally an account of the model's use in a commercial harbour design study. Most alternative computational harbour modelling techniques are limited by computational effort.to small harbour areas and/or long wavelengths. The new model is designed for the opposite case, of large harbour areas and short waves. The main theoretical problem is the construction of a ray system to represent breakwater diffraction. The conventional method of tracing rays radially from the breakwater tip is shown to break down in an unbounded area surrounding the geometric shadow boundary. A completely new ray system is adopted in this work which involves tracing rays from the shadow boundary rather than the breakwater tip. This method is shown to make good predictions of wave heights and directions everywhere except in a very small bounded area surrounding the breakwater tip. Full numerical comparisons of the new ray method with the radial ray method and Sommerfeld's analytical solution are carried out. A computational model is then developed in which this new ray tracing technique for breakwater diffraction is combined with refraction due to arbitrarily varying depth profiles, and reflections from harbor boundaries with general plan shapes and reflection coefficients. The model also includes a new technique of interpreting ray diagrams to obtain wave heights and directions in a general manner, overcoming most of the problems associated with earlier methods. This new computational model is compared against a finite-element model for a simplified harbour layout, and then against a random-wave physical model of an actual harbour design in which the processes of wave I diffraction, refraction and reflection are combined in a general manner. Finally, the computational ray model is used in parallel with a physical model in a commercial investigation, and an assessment of the merits of the computational model as a commercial tool is made

Non-Linear Evolution of Steady and Migrating Alternate Bars in a Straight Channel (abstract)

This paper contains an analysis of a long-duration experiment that shows the evolution of alternate bars in a straight channel. The theoretical predictions are based on a weakly non-linear theory of the morphological development. Both the experiment and theory have several innovative features.Hydraulic EngineeringCivil Engineering and Geoscience

Dune development and aeolian transport along the Holland coast

Hydraulic EngineeringCivil Engineering and Geoscience