Wave damping by dynamic breakwaters: Modelling and experiments

A new and innovative idea to reduce the wave reflection in front of vertical walls is by means of dynamic breakwaters, which dissipate wave energy by using moving elements. These moving elements in combination with a spring and a 'dashpor' to dissipate energy reduce the wave reflection in a wide range offrequencies (see Figure 2-1, 2-2 for pictures). In a previous study the wave-damping characteristics of a dynamic breakwater with a horizontal translating flap has been investigated [SMIT, 1999]. Such a structure appears to be able to damp waves in a wide range of frequencies. However, the model derived in that study is based on long-wave theory and also neglects some other hydrodynamic aspects. Since the intended application of a dynamic breakwater will be in short waves, a new study has been performed. The first objective of this research is to develop an analytic model of the wave damping characteristics of a dynamic breakwater. The model intents to describe the dynamic behaviour of the flap and predict the wave reflection in a wide range of wave frequencies. The second objective is to acquire quantitative data on wave reflection by experiments with a hydraulic model. The third objective is to analyse the experimental data in relation to the analytic model.Hydraulic EngineeringCivil Engineering and Geoscience