Flow Field Analysis and Performance of Wind Turbines Employing Slotted Diffusers

Operation of diffuser-augmented wind turbines (DAWTs) utilizing slotted walls for tangential blowing as a boundary layer control measure has been analyzed using the method of singularities (MOS). The diffuser wall and the drop in total pressure through the turbine are represented by a series of ring vortices along the diffuser surface and along the wake boundary. Diffuser included angles of 60 to 80 deg are considered, in contrast to the conventional range of 7 to 10 deg. Agreement with Grumman Research Department experimental data with respect to overall performance and pressure and velocity distributions is reasonably good. In particular, the existence of the observed large pressure reduction at the diffuser exit plane is predicted. A consequence of this agreement is that Reynolds number scaling effects are small for slotted DAWTs, so that MOS analyses hold promise for other innovative diffuser designs and flow problems.