Drag reduction of large wind turbine blades through riblets: Evaluation of riblet geometry and application strategies

摘要: Abstract Wind tunnel experiments were performed to quantify the drag reduction on a wind turbine airfoil partially or fully covered with riblets. A full-scale 2.5 MW section, typical for near tip, was placed in free stream flow of at Saint Anthony Falls Laboratory, University Minnesota. Various sizes and geometries experimental riblets provided by 3M Company tested angles attack ranging from 0° ≤ α ≤ 10° (0.25 ≤ CL ≤ 1.14) Reynolds number Re = 2.2 × 106. Mean measured via wake survey (momentum deficit) sensitive force balance. Lift directly Tests included cases complete partial riblet coverage wing. Results indicated that could provide an overall skin friction drag, amount decrease varied height geometry. Partial appears some more efficient than its counterpart. The percentage reduced greatly even detrimental airfoil. most completely found be V-groove shape 100 μm height. It produced roughly 6% operational range expected On other hand, size also seemed shift slightly smaller peak 80 μm. This configuration 4% angle is operation field. average non-dimensional square root groove cross-section, l+, defined terms coefficient design optimum case l + ≈ 10 , which very close value planar surfaces. Based our results we propose formulation considering mean chord length number. Even though full showed better performance case, additional benefit may offset application cost.