Sensitivity of wind turbine airfoil sections to geometry variations inherent in modular blades

In the ongoing work to increase the efficiency of large-scale, horizontal-axis wind turbines, the modular blade concept has been proposed. This article works toward quantifying the aerodynamic performance of modular blades, whose baseline profile remains unchanged from conventional blades but which are susceptible to a larger degree of variation in both manufacturing tolerances and fabrication materials, by examining the effects of offsets in the leading edge and the use of a tensioned membrane-fabric as a flow surface over the aft. Wind tunnel tests were performed on modified DU00-W-212 and DU91-W2-250 sections and included standard pressure measurements, as well as surface deflection measurements of the fabric. For the case of offsets near the nose of the profile, the offsets produce up to 17% decrease in C l / C d . For the case of fabric in the aft of the model, the C l / C d variations are strongly dependent on the spanwise location of the measurement