Investigation of the nacelle blockage effect for a downwind turbine

As downwind turbines garner increasing research interest, nacelle blockage becomes an important consideration. This paper examines nacelle blockage effects under a variety of Reynolds numbers, turbulence intensities, and nacelle geometries and proposes a computationally inexpensive nacelle blockage engineering model. Results show minimal nacelle blockage impacts on rotor loading and performance, except for tall (low-aspect-ratio) nacelles, which can cause an increase in rotor C p of up to 0.6%. In all cases, nacelle blockage increases rotor loading and performance metrics, however little. Finally, (more expensive) geometry-resolved and (less expensive) body-force computational fluid dynamics modeling techniques are compared, and body-force models are found to need improvement to adequately model nacelle blockage.