Abstract: The paper presents a computational study of a bidirectional ducted turbine for extracting energy from tidal streams. The flow through the ducted turbine is modelled through solution of the Reynolds-averaged Navier-Stokes (RANS) equations in which the turbine is modelled as a porous disc that imposes a resistance to the passage of the flow.
The paper first presents a validation of the technique for the case of an unducted turbine operating in unconfined flow. The performance of the turbine, power and thrust coefficients, are compared favourably to Betz theory. Following this validation the case of the bi-directional ducted turbine operating in unconfined flow is presented. Simulation results show that the turbine’s power coefficient, defined based on the rotor swept area, can be modestly increased through the use of the duct. The increase in power coefficient is accompanied by an increase in the overall thrust acting on the device.
