Numerical method for the characterization of sea states using realistic irregular waves on computational fluid dynamics simulations for application on wave energy converters

Abstract

Energy demand grows along with technological advances, industrial expansion, and global urbanization. To supply this demand sustainably, there are several attempts to harness energy from renewable sources, among them, wave energy. The study of wave energy availability in energy conversion devices primarily focuses on two major areas: analysis of the fluid-dynamic behavior of the devices and the simulation of sea states to estimate theoretical energy potential. Despite advancements in both fields, there is a lack of methodologies that effectively integrate realistic irregular wave simulations and fluid-dynamic analysis of energy conversion devices. This research aims to integrate these areas by employing the WaveMIMO methodology, in which a sea state spectrum is converted into a statistically equivalent time series of water free surface elevation, then applied as an estimation of the velocity field in the water column to generate irregular waves. This study focuses on the development of a methodology to characterize the wave climate in the city of Rio Grande, in southern Brazil, for the year 2014, using a histogram to classify sea states according to their significant wave height and mean wave period, thus producing a bivariate histogram of wave conditions. A sea state spectrum was obtained for each pair of wave height and period and simulated using the computational fluid dynamics software Fluent to reproduce the realistic irregular waves of this sea state. The results indicated that the methodology for categorizing the sea state based on a histogram proved to be a computationally efficient alternative for the numerical simulation of wave climates in a given location for a long period of time, reducing the simulation time needed to approximately 0.5% of the total amount. In addition, an application of this methodology to investigate the wave energy conversion employing an oscillating water column device is presented as supplementary material.