Research Papers: Alternative Energy Sources

Multivariable Analysis of Aerodynamic Forces on Slotted Airfoils for Wind Turbine Blades

[+] Author and Article Information
Saman Beyhaghi

Department of Mechanical Engineering,
University of Wisconsin-Milwaukee,
3200 N. Cramer Street,
Milwaukee, WI 53211
e-mail: beyhagh2@uwm.edu

Ryoichi S. Amano

Fellow ASME
Department of Mechanical Engineering,
University of Wisconsin-Milwaukee,
3200 N. Cramer Street,
Milwaukee, WI 53211
e-mail: amano@uwm.edu

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received July 17, 2018; final manuscript received February 17, 2019; published online April 10, 2019. Editor: Hameed Metghalchi.

J. Energy Resour. Technol 141(5), 051214 (Apr 10, 2019) (10 pages) Paper No: JERT-18-1543; doi: 10.1115/1.4042914 History: Received July 17, 2018; Revised February 17, 2019

Improvement of the aerodynamic performance for cambered airfoils with leading-edge slots is investigated in this work. This concept is proven both computationally and experimentally in recent years. Five design variables of interest are slot's length, slot's width or thickness, inlet angle, exit angle, and the vertical position. The objective is to perform design of experiment and optimization studies on these variables and evaluate the behavior of the objective functions, namely lift and lift over drag ratio (LoD), within the appropriate ranges of the independent variables. Simulations are mainly carried out at the Reynolds number of 1.6 × 106 and the angles of attack (AoA) of 6 deg for NACA 4412 airfoil. However, some of the analyses are repeated at Reynolds number of 3.2 × 106 and AoA of 0 and 8 deg to show the scalability of the results. Results indicate that the proper selection of three of the design variables, i.e., length, inlet angle, and vertical position, can have a significant impact on both lift and LoD, while the other two variables seem less influential. For the combination of the operating conditions and the values of the design variables considered in this investigation, a LoD improvement as large as 11% is observed.

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Fig. 1

The slotted wind turbine blade fabricated and tested at UWM wind tunnel

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Fig. 2

A sample NACA 4412 slotted airfoil with the design variables depicted

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Fig. 3

(a) The computational domain used for the analysis of the slotted airfoil, (b) the overall view of the mesh, and (c) magnified view of the mesh near the leading edge and the slot

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Fig. 4

An LHS design with nine total points

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Fig. 5

Distribution of the data points in the current DoE study for (a) ten evaluations considered for L1 and w study, and (b) 12 evaluations considered for β1 and β2 study

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Fig. 6

Response surfaces fitted to (a) lift and (b) LoD data points for a DoE study on L1/c and w/c

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Fig. 7

Response surfaces fitted to (a) lift and (b) LoD data points for a DoE study on the inlet angle β1 and the exit angle β2

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Fig. 8

Response surfaces fitted to (a) lift and (b) LoD data points for a DoE study on L1/c and h

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Fig. 9

The objective function LoD monitored in the optimization study with a maximum of 40 evaluations

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Fig. 10

Response surfaces fitted to LoD data points for a DoE study with Re = 1.6 × 106 and AoA = 8 deg on (a) L1/c and w/c, (b) β1 and β2, and (c) L1/c and h/c

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Fig. 11

Comparison of LoD as a function of L1 and w for three different AoA cases

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Fig. 12

Response surfaces fitted to LoD data points for a DoE study with Re = 3.2 × 106 and AoA = 6 deg on (a) L1/c and w/c, (b) β1 and β2, and (c) L1/c and h/c

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Fig. 13

Response surface fitted to (a) lift and (b) LoD data points for a DoE study on NACA 0012 airfoil profile with Re = 1.6 × 106 and AoA = 6 deg



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