GEOMETRIC EVALUTION OF THE RAMP OF AN OVERTOPPING DEVICE BY MEANS OF CONSTRUCTAL DESIGN AND A WAVE SPECTRUM
Jaifer Corrêa Martins1; Elizaldo Domingues dos Santos2; Liércio André Isoldi2; Mateus das Neves Gomes3; Luiz Alberto Oliveira Rocha4
1 Universidade Federal do Rio Grande do Sul, Rua Sarmento Leite, 425, Porto Alegre, RS, 90.050-170; 2 Universidade Federal do Rio Grande, Av. Itália, km 8, Cx.P. 474, Rio Grande, RS, 96201-900; 3 Instituto Federal do Paraná, Rua Antonio Carlos Rodrigues, 453, Paranaguá, PR, 83215-750; 4 Universidade do Vale do Rio dos Sinos, Av. Unisinos, 950, São Leopoldo
doi:10.20906/CPS/CILAMCE2017-0549
Resumo
The study about Wave Energy Converters (WECs), technologies and operational principles of devices, has increased significantly over the years. Among the studied WECs it is possible to mention the overtopping device. Its main operational principle consists on a ramp which guides the incoming waves into a reservoir close by the sea water level (SWL). The accumulated water in the reservoir flows through a low head turbine generating electricity. The purpose of this numerical study is to evaluate the effect of four ramp area fraction ( = 0.0006, 0.0009, 0.0012 and 0.0015), three ratio between the height and length of the ramp (H1/L1 = 0.3, 0.5 and 0.7) and two forms to fixed the ramp height (midpoint and height) over the device available power (Pa). The device is an onshore overtopping in real scale subject to a Pierson-Moskowitz (PM) wave spectrum. Constructal design associated to the exhaustive search optimization method was used to discover the best geometries for the ramp. The PM wave spectrum has also the wave period and the wave height fixed (TS = 7.5 s, and HS = 1.5 m). The conservation equations of mass, momentum and one equation for the transport of volumetric fraction are solved with the Finite Volume Method (FVM), for all studied cases. To tackle with water-air mixture, the multiphase model Volume of Fluid (VOF) is used. The results showed that Constructal Design allowed an improvement of the shape of ramp and the wave spectrum makes the simulation closer to the real phenomenon. Moreover, the area fraction of ramp (ϕ), different ratio between height and length of the ramp (H1/L1) and the forms to fixed the ramp height (midpoint and height), has strong influence over the available power (Pa).
Palavras-chave: Onshore overtopping; Constructal design; Volume of fluid; Geometric evaluation; Wave spectrum