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research-article

Static and dynamic analysis of a NACA 0021 airfoil section at low Reynolds numbers based on experiments and CFD

[+] Author and Article Information
Francesco Balduzzi

Department of Industrial Engineering, Università degli Studi di Firenze, Via di Santa Marta 3, 50139, Firenze, Italy
balduzzi@unifi.it

Alessandro Bianchini

Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623, Berlin, Germany
bianchini@vega.de.unifi.it

Lorenzo Ferrari

Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623, Berlin, Germany
lorenzo.ferrari@unipi.it

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

Felix Wegner

Chair of Fluid Dynamics, Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623, Berlin, Germany
felix.wegner5@googlemail.com

Georgios Pechlivanoglou

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

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

Giovanni Ferrara

DESTEC, Università di Pisa, Largo Lucio Lazzarino, 56122, Pisa, Italy
lorenzo.ferrari@unipi.it

1Corresponding author.

ASME doi:10.1115/1.4041150 History: Received July 03, 2018; Revised July 20, 2018

Abstract

The wind industry needs airfoil data for ranges of Angle of Attack wider than those of aviation applications, since large portions of the blades may operate in stalled conditions for a significant part of their lives. Vertical axis turbines are even more affected, since data across the full range of 180degree is necessary for a correct performance prediction. The literature lacks data in deep and post stall regions for nearly every airfoil. The present study shows experimental and numerical results for the NACA 0021 airfoil, which is often used for Darrieus VAWT design. Experimental data were obtained through dedicated wind tunnel measurements of the airfoil with surface pressure taps, which provided further insight into the pressure coefficient distribution across a wide range of AoAs. The measurements were conducted at two Reynolds numbers, 140k and180k. Each experiment was performed multiple times to ensure repeatability. Dynamic AoA changes were also investigated at multiple reduced frequencies. Moreover, dedicated unsteady numerical simulations were carried out on the same airfoil shape to reproduce the static polars and some relevant dynamic AoA variation cycles tested in the experiments. The solved flow field was exploited to get further insight into the flow mechanisms highlighted by the wind tunnel tests and to provide correction factors to discard the influence of the experimental apparatus, making experiments representative of open-field behaviour. The present study is thought to provide the scientific community with high quality, low-Reynolds data, which may enable in the near future a more effective VAWT design.

Copyright (c) 2018 by ASME
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