The spatial uniformity of a wave field in a wave basin is essential for the accuracy of seakeeping tests of ships. However, the height of regular waves generated based on the “snake motion” principle is known to be distributed nonuniformly in a wave basin. One of the major causes of this spatial nonuniformity is the cylindrical propagation property of waves generated from a limited width of the wave-maker array compared with a tank width. The same phenomenon is also observed in a wave basin with wave-makers all around the perimeter.Therefore, in this study, we developed an optimization methodology of segmented wave-makers control to generate spatially uniform regular waves in a limited area (test zone) of a wave basin with wave-makers all around the perimeter.&nbsp; We set the coefficient of variation (CV) of the wave heights in the test zone as an objective function to be minimized. The wave-makers motions are optimized by the simulated annealing, one of the algorithms to solve a global optimization problem, in combination with a time-domain numerical wave tank (NWT) based on the potential theory. In the optimization, we impose a constraint on the adjacent wave-makers’ motion to avoid a large gap between them.A wave generation experiment was performed in the Actual Sea Model Basin (80m long, 40m wide, and 4.5m deep) at the National Maritime Research Institute to validate the proposed optimization methodology. A 40m × 14m test zone was set in the middle of the basin. A case study was carried out for a regular wave with a wavelength of 4m, wave height of 10 cm, and wave direction of 180 degrees corresponding to the longer direction of the wave basin. We chose this wave direction because the spatial nonuniformity of the wave field is most significant. As a result of the optimization, the NWT computation indicated that the optimal solution suppresses the wave height CV in the test zone about a quarter compared with the conventional snake motion wave generation. Based on the optimal and the snake motion wave-maker signals, we physically conducted wave generation experiments. Consequently, we revealed that the optimal wave-makers control effectively reduced the wave height CV in the test zone compared with the snake motion wave generation.

Optimization of Segmented Wave-Maker Control to Generate Spatially Uniform Regular Waves in a Rounded-Rectangular Wave Basin

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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