Adaptation of Second Order Wavemaker Theories to the CIEMito Wave Flume

Abstract

Coastal engineering deals with complex systems that involve processes that are not fully understood. Physical modeling has become an important tool in the study of these processes. It allows researchers to control the conditions that are being studied, and simplify the system to include only what is desired. In a coastal system waves are often one of the main driving forces of these processes. Because of this it is of great importance to have the ability to reproduce the natural wave conditions in the laboratory settings. When generating waves with a low relative water depth, and/or a high wave steepness using first order wavemaker theory the resulting waves are contaminated with an unwanted secondary wave, which causes the generated wave profile to change as the wave travels along the wave flume. The aim of this study is to find under which conditions this issue takes place in the CIEMito wave flume of the Laboratori d’Enginyeria Marítima (LIM), and to implement a second order wavemaker theory capable of suppressing it. Several wavemaker theories were studied, the first order wavemaker theory, and several second order wavemaker theories. Due to issues arising with the implementation of most of the second order theories, only the first order wavemaker theory and the second order wavemaker theory given by Madsen (1971) were applied to the CIEMito wave flume. Thirty-seven different wave conditions were tested in the CIEMito wave flume using first order wavemaker theory. From this the issues with first order wave generation were studied. Due to issues with the physical wave flume the second order theory could not be tested there. Instead, a numerical wave flume based on PFEM (particle finite element method) was validated so that the CIEMito wave flume could be simulated with this numerical model. Four of the wave conditions tested in the physical wave flume were simulated using both first order and second order Madsen wavemaker theory. From this the capability of Madsen’s second order wavemaker theory of suppressing the unwanted secondary waves was assessed.