ABSTRACT

A numerical tool has been developed to predict the impulsive hydrodynamic uplift loads produced by cnoidal waves impacting coastal structures. A nonlinear cnoidal II wave theory is adopted. The finite-element method is used to solve the Laplace equation and the Height-Flux Method (HFM) is employed to trace the motions of the free surface in the time domain. A numerical wave tank is established with a piston wavemaker to generate nonlinear cnoidal II waves. The cnoidal waves produced by the wavemaker have been verified by comparing the wave profile with second-order analytic solutions and very good agreement is shown. Predictions of the impulsive uplift loads produced by cnoidal waves have shown reasonable trends in comparison with impulsive uplift loads produced by solitary waves.

INTRODUCTION

The interaction of waves with marine structures has been studied by civil, ocean and marine structural engineers using experimental and analytical methods. One of the most important problems involved in wave-structure interaction is the accurate prediction of wave loads on structures. Predictions of external loads due to wave impact and uplift can provide engineers with reliable design loads, which can be used to calculate the structural response, including structural displacements, stresses and bending moments.

Offshore structures (such as oil-drilling platforms) constructed in relatively deep water normally interact with non-breaking waves. Nearshore structures (such as docks and dolphins) constructed in coastal regions are often attacked by waves that have been transformed by the sloping beach near those structures. It follows that development of new software to predict wave forces acting on offshore and nearshore structures will play a very important role in the design of these structures by engineers. Based experimental observations, cnoidal waves are frequently formed in the relatively shallow waters of the nearshore region, and these wave forms must therefore employed when designing coastal structures.

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