Smoothed particle hydrodynamics study of a heaving point absorber in various waves using wave tank and calm-water models

Abstract

In this research, the influence of wave parameters on the response of a tuned point absorber was evaluated using the smoothed particle hydrodynamics (SPH) wave tank and calm-water models. In the first model, the device response was obtained under the effect of waves generated by a wavemaker. In the calm-water model, the added mass and hydrodynamic damping coefficients of the device were calculated from a short-time SPH-free decaying test. Then, using the Runge–Kutta method, the governing equation of motion was solved in MATLAB. Both models were verified by previously published experimental tests. Considering the viscous damping makes calm-water model superior to potential-flow models. Meanwhile, the computation time of this model is very lower than wave tank model. For wave steepness values below 8.5% which is more than the upper limit of wave steepness for deep-water waves, both models predicted a direct relationship between wave height and device motion. However, wave tank simulations showed that for steeper waves, the device motion was not significantly affected by the wave height. Moreover, the device response decreased as the wave period moved away from the device's natural period. The predictions of the two models had an average difference below 10%. While in linear conditions, the calm-water model predicted a slightly larger response than the wave tank model; in nonlinear cases, wave tank model predicted slightly higher device motions. This research shows that using the SPH calm water model is an efficient way to investigate wave-point absorber interactions.