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research-article

Experimental Analysis of a NACA 0021 Airfoil Section Through 180-Degree Angle of Attack at Low Reynolds Numbers for Use in Wind Turbine Analysis

[+] Author and Article Information
David Holst

Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623 Berlin, Germany
david.holst@tu-berlin.de

Benjamin Church

Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623 Berlin, Germany
church.benni@gmail.com

Georgios Pechlivanoglou

Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623 Berlin, Germany
george@pechlivanoglou.com

Ergin Tüzüner

Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623 Berlin, Germany
e.tuezuener@web.de

Joseph Saverin

Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623 Berlin, Germany
j.saverin@tu-berlin.de

Christian Navid Nayeri

Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623 Berlin, Germany
christian.nayeri@tu-berlin.de

Christian Oliver Paschereit

Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623 Berlin, Germany
oliver.paschereit@tu-berlin.de

1Corresponding author.

ASME doi:10.1115/1.4041651 History: Received August 20, 2018; Revised September 08, 2018

Abstract

Wind turbine industry has a special need for accurate post stall airfoil data. While literature often covers incidence ranges [-10deg;+25deg] smaller machines experience a range of up to 90 deg for horizontal axis and up to 360 deg for vertical axis wind turbines (VAWTs). The post stall data of airfoils is crucial to improve the prediction of the start-up behavior as well as the performance at low tip speed ratios. The present paper analyzes and discusses the performance of the symmetrical NACA 0021 airfoil at three Reynolds numbers (Re = 100k, 140k, and 180k) through 180 deg incidence. The typical problem of blockage within a wind tunnel was avoided using an open test section. The experiments were conducted in terms of surface pressure distribution over the airfoil for a tripped and a baseline configuration. The pressure was used to gain lift, pressure drag, moment data. Further investigations with positive and negative pitching revealed a second hysteresis loop in the deep post stall region resulting in a difference of 0.2 in moment coefficient and 0.5 in lift.

Copyright (c) 2018 by ASME
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