Comparative study on the breaking waves by a piston-type wavemaker in experiments and SPH simulations

ABSTRACT

The wave transfer function derived from the linear wavemaker theory has been widely applied to validate the accuracy of the regular wave. However, it is limited to analyze the waves with large wave steepness, short wavelength, or breaking wave generated right on the wave paddle. By introducing the piston stroke-to-water depth ratio, the empirical formula in the literature is modified to predict both regular and breaking waves according to the wave steepness. Using an experimental wave flume, regular and breaking waves are generated by manipulating the target wave steepness and stroke-to-water depth ratio. The proposed equation is verified in accordance with the experiment results, and optimal variables including energy loss coefficient and breaker index are presented by analyzing the root-mean-square errors. With the developed equation, wave heights and relative depths from any type of piston-type wavemaker can be predicted if the variables of the proposed equation are properly adjusted. Additionally, the numerical wave tank (NWT) is modeled by smoothed particle hydrodynamics (SPH), and the numerically calculated wave heights show good agreement with the proposed equation. The developed methodology can be employed as a guideline toward further studies including analyses of structural behavior under the breaking wave.

KEYWORDS:

• Smoothed particle hydrodynamics (SPH)
• numerical wave tank (NWT)
• wave steepness
• breaking wave
• piston-type wavemaker

Additional information

Funding

This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korean government (Ministry of Science and ICT) [No. 2017R1A5A1014883], and was also a part of the project titled “Construction of Ocean Research Station and their Application Studies” funded by the Ministry of Oceans and Fisheries, Korea.