Drag Estimation in the Near Wake of the NREL's Airfoils Based on Hot-Wire Data

This paper presents the results of the drag coefficient estimations for different types of NREL airfoils based on the experimental data. Namely, it was S803, S807, S813, and S817 profiles with the same chord length. The investigations were conducted at three angles of attack α=0°, α=±5°, different chord-based Reynolds numbers 0.6×105, 1.3×105 and 2.6×105. While, measuring cross-sections were placed behind the trailing edge at x∙c−1≈0.2, 0.4 and 1.0. Experimental data were collected using a hot-wire split fiber probe 55R55, which allowed us to estimate the characteristics of turbulent flow in stream-wise and crosswise directions. According to the obtained results, the highest and lowest Cd values correspond to profiles S817 and S803, respectively. Moreover, the results show that more asymmetric profiles S803 and S807 have the lowest resistance at zero angles of attack. Research background: Application of Antonia and Rajagopalan methodology to drag assessment of various stream bodies. Purpose of the article: Comparative evaluation of the drag coefficients of the NREL airfoils based on instantaneous velocity distribution behind. Methods: Hot-wire anemometry with split fiber probe 55R55. Findings & Value added: The highest drag coefficient corresponds to the S817 profile. The asymmetry of the airfoil shape has a significant impact on its drag characteristics