Dynamic Response Analysis of a Wavestar-Type Wave Energy Converter Using Augmented Formulation in Korean Nearshore Areas

Interest in water wave power generation, a promising source of renewable energy, is increasing. Numerous types of wave energy converters (WECs) have been designed to transform wave energy into electricity. In this study, we focus on heaving point absorbers (HPAs) of the Wavestar type, which consist of multiple floats connected to a bottom-fixed ocean structure by structural arms and hinges. Each float moves up and down due to wave forces and produces electricity using the hydraulic power take-off (PTO) system connected directly to the float. A numerical procedure using the three-dimensional augmented formulation was developed to calculate the rotational motion of the float. The frequency-dependent coefficients were calculated using the hydrodynamic solver WAMIT. The nonlinear Froude–Krylov and hydrostatic forces were considered. For the environmental conditions, the wave data of four nearshore areas in Korea, obtained from the Korea Meteorological Administration (KMA), were used. Under the given environmental conditions, Buan was found to be the most suitable area among the locations selected for installing a Wavestar-type WEC without considering installation and maintenance costs.

Implementing the Extended Reduced Order Physical Model Into Commercialized Software Packages: Implementing Modal Constraints Into Software Packages

In this paper, the extended reduced order physical model, which is developed to represent dynamics of flexible structures in multibody systems, is implemented to general multibody formulations. The elastic deformations are described using vibration modes associated with the rigid bodies that are effectively defined using dynamic properties of the system in this reduced order modeling method. The recursive formulation and the augmented formulation are used to develop the constraint equations associated with the connections between the reference body and the several rigid bodies in the modal representations used to modal elastic deformations. For this purpose, the n-body constraint is developed for the recursive formulations, while these constraint equations are transformed into the form that is suitable for the augmented formulation using the singular value decomposition or QR decomposition. The use of the formulations in this paper allows for the implementation of the extended reduced order physical model into the commercial multibody codes such as SIMPACK, ADAMS, and DADS.