Chapter 7 - A CFD-based study of cross-flow turbine for tidal energy extraction

Abstract

A considerable interest in exploiting tidal currents for power generation has led to extensive studies on this source of renewable energy. Turbines utilizing the marine streams consume the kinetic energy of the currents and convert it to mechanical energy. computational fluid dynamics (CFD) plays a major role in fluid flow–related studies. The present study deals with the key parameters which influence the turbine performance. The power, power coefficient (PC) and torque of the tidal cross-flow turbine (CFT) depends on several design parameters such as tip speed ratio (TSR), inlet and outlet blade angle, internal diameter, angle of attack, number of blades, and augmentation channel inlet area. The internal flow characteristic of the turbine has been studied for various cases. A standard CFT model with augmentation channel dimensions of 3.2m×1.6m is modeled with rotor having 30 blades, 464mm length in radial direction and 3.2m axial length, 300 inlet and radial outlet. The study reports the torque, power, and PC with channel under high as well as low tides. The boundary conditions taken are inlet velocity of 2.5m/s, relative pressure of 0Pa at outlet, and the reference pressure is atmospheric with walls modeled under free slip condition. Using pressure–velocity coupling scheme, SIMPLE and k-ε turbulence model, the velocity vectors have been reported for both, high tide, and low tide. The model is validated with existing benchmarks and reasonable agreement is observed. A parametric study is reported by varying the internal diameter of the rotor and inlet blade angle. The plots of power, PC, and torque with TSR is presented and discussed.