Numerical and experimental assessment of hydrodynamic force of a heaving porous disk

New Strategy on Power Absorption of a Concentric Two-Body Wave Energy Converter

“…In addition, this approach can save the cost of protecting the WEC system against excessive motion of the WEC as well as the cost of manufacturing a large PTO system to accommodate amplified mechanical power in resonance. As described in Section 2.5, the viscous damping due to the formation of vortices at the disk edge can be implemented by the drag force inspired by the Morison equation, with the drag coefficient determined by curve fitting of the experimental data in the form of C d = 6.5(KC) −1/3 [16], where KC = π|ξ 1 |/a 3 . In Figure 9, the heave RAO obtained from the viscous damping from the drag force shows better predictions than that from the free-decay test near the resonance frequency.…”

“…To implement the effect of viscous damping due to the edge vortices of the heave disk, an empirical formula for the drag coefficient C d in Equation ( 23) should be determined. The empirical formula for C d is obtained through curve fitting of the experimental data in the form of C d = 6.5(KC) −1/3 , as presented in [16], where the KC number is defined as KC = π|ξ 1 |/a 3 .…”

“…The varied parameters included the submerged distance from the free surface, plate porosity, porous hole size, plate thickness-to-width ratio, edge shape, and the spacing of stacked heave plates. The authors of [16] reported numerical and experimental hydrodynamic assessments of a heaving porous disk and presented the drag coefficient in terms of KC and porosity. The existing literature on heave plates provides a strong base for further research on the use of heave plates for wave energy conversion.…”

“…To realize the effect of the heave disk, the viscous damping dominated by the formation of vortices at the edge of the disk is modeled using the equivalent linearized drag force with the Morison equation. The drag coefficient is empirically expressed as a function of the KC number by experiments [16]. The optimal power of a two-body WEC has been extensively investigated for various design parameters in irregular-wave conditions.…”