The load of breaking waves distinguishes from the impact of non -breaking waves in the superposition of an additional, transient force of short duration. A simple method is presented to decompose the quasi -static force, the periodic part of the total measured force, and the dynamic component, which is the response of the cylinder due to the additional impact. The method is verified with large-scale model tests. The tests were carried out in the Large Wave Channel (GWK) with a slender, vertical and inclined cylindrical pile located at the end of a 1:10 slope. Finally the impact and the curling factor λ, an empirical coefficient to calculate the height of the impact area, is determined and compared to published data from laboratory deep water experiments.
Large-scale model tests were carried out in the Large Wave Channel (GWK) with a slender cylindrical pile located at the end of a 1:10 slope. The test cylinder was subject to both regular and irregular waves. The paper deals with (i) the evaluation of the breaker characteristics at the breaking point for the test conditions, (ii) the comparison of the results with published data from small-scale experiments and (iii) the measured vertical distribution of horizontal particle velocities under a breaking wave. Additionally a new method of separating the measured force history into a slowly varying quasi-static and a dynamic part is presented by using the EMD (Empirical Mode Decomposition) for the analysis of breaking wave attack.
Large scale experiments have been conducted in the LARGE WAVE CHANNEL of the Forschungszentrum Küste (Coastal Research Centre) in Hannover to investigate the loads acting on a slender circular cylinder attacked by a breaking wave. The wave kinematics, the impact and the cylinder's response were measured simultaneously. For the load measurement two independent methods were used. On the one side pressures were measured and on the other side forces were determined at the bearings. Analysing the data a theoretical description for the two-dimensional impact is confirmed and peak values for the three-dimensional impact are obtained. It is shown that the commonly used calculation method for the impact force fails because the duration of impact is overestimated.
This paper presents results of large scale experiments with various cylinder groups in tandem and side by side configurations. The transverse and inline forces have been investigated in regard to the vortex shedding processes, and the influences of neighboring cylinders on the wave load of a single isolated cylinder are pointed out. Furthermore, the Co and CM coefficients as well as the drag force and added mass characteristics were investigated by the method of the least square fit for the cylinder groups with diverse center to center spacing.
Based on large scale experiments theoretical formulae for the load due to breaking wave impact on slender piles have been developed. The load distribution in time and space is given by the proposed theoretical 3D-impact model. The formulae are applied to calculate the impact force on a support tower of a wind turbine subjected to breaking wave. The bending moment at the base of the support tower can also be determined.
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