Effect of Nacelle Shape on the Flow Fields of Upwind and Downwind Wind Turbines

This work compares aerodynamic loads, power outputs and wake fields of upwind and downwind wind turbines. To that end, wind tunnel experiments are performed with model wind turbines with cylindrical and ellipsoidal nacelles, to investigate whether the nacelle shape changes the performance or flow characteristics of the turbine configurations. The thrust and the power coefficients of both upwind and downwind turbines show similar trends with no significant difference between peak power coefficients of the two configurations. For the laminar and uniform inflow conditions, wind speed is slightly higher around the rotor centre in the wake of the downwind turbine. However, the effect of nacelle shape to the wake field is not significant. Turbulence intensity profiles for upwind and downwind configurations do not show significant differences and peak values of turbulence intensities can be observed around the rotor tip region. Differences between turbulence profiles for experiments with cylindrical and ellipsoidal nacelles are negligible. The study shows that downwind turbines with both types of nacelles showed comparable performance and wake characteristics to their upwind counterparts. Therefore, they can be scaled up with flexible and cheaper blades, without having to compromise in terms of turbine performance.