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Assessment of digital image correlation as a method of obtaining deformations of a structure under fluid load

Assessment of digital image correlation as a method of obtaining deformations of a structure under fluid load
Assessment of digital image correlation as a method of obtaining deformations of a structure under fluid load
Digital Image Correlation (DIC) is employed for the measurement of full-field deformation during fluid-structure interaction experiments in a wind tunnel. The methodology developed for the wind tunnel environment is quantitatively assessed. The static deformation error of the system is shown to be less than 0.8% when applied to a curved aerofoil specimen moved through known displacements using a micrometer. Enclosed camera fairings were shown to be required to minimise error due to wind induced camera vibration under aerodynamic loading. The methodology was demonstrated using a high performance curved foil, from a NACRA F20 sailing catamaran, tested within the University of Southampton RJ Mitchell, 3.5m x 2.4m, wind tunnel. The aerodynamic forces induced in the wind tunnel are relatively small, compared with typical hydrodynamic loading, resulting in small deformations. The coupled deflection and blade twist is evaluated over the tip region (80-100% Span, measured from the root) for a range of wind speeds and angles of attack. Steady deformations at low angles of attack were shown to be well captured however unsteady deformations at higher angles of attack were observed as an increase in variability due to hardware limitations in the current DIC system. It is concluded that higher DIC sample rates are required to assess unsteady deformations in the future. The full field deformation data reveals limited blade twist for low angles of attack, below the stall angle. For larger angles, however, there is a tendency to reduce the effective angle of attack at the tip of the structure, combined with an unsteady structural response. This capability highlights the benefits of the presented methodology over fixed-point measurements as the three dimensional foil deflections can be assessed over a large tip region. In addition, the methodology demonstrates that very small deformations and twist angles can be resolved.
wind tunnel tests, digital image correlation, fluid structures interaction, composite materials, aeroelastic tailoring
0889-9746
173-187
Banks, Joseph
3e915107-6d17-4097-8e77-99c40c8c053d
Marimon Giovannetti, Laura
9fada37b-24b2-4235-aa91-e8c25837953d
Soubeyran, Xavier
7c5205b6-46f0-4627-8922-926afce1572c
Wright, Alexander
e4d631cc-fe6a-4abf-b99d-b6e8262a0bd3
Turnock, Stephen
d6442f5c-d9af-4fdb-8406-7c79a92b26ce
Boyd, Stephen
bcbdefe0-5acf-4d6a-8a16-f4abf7c78b10
Banks, Joseph
3e915107-6d17-4097-8e77-99c40c8c053d
Marimon Giovannetti, Laura
9fada37b-24b2-4235-aa91-e8c25837953d
Soubeyran, Xavier
7c5205b6-46f0-4627-8922-926afce1572c
Wright, Alexander
e4d631cc-fe6a-4abf-b99d-b6e8262a0bd3
Turnock, Stephen
d6442f5c-d9af-4fdb-8406-7c79a92b26ce
Boyd, Stephen
bcbdefe0-5acf-4d6a-8a16-f4abf7c78b10

Banks, Joseph, Marimon Giovannetti, Laura, Soubeyran, Xavier, Wright, Alexander, Turnock, Stephen and Boyd, Stephen (2015) Assessment of digital image correlation as a method of obtaining deformations of a structure under fluid load. Journal of Fluids and Structures, 58, 173-187. (doi:10.1016/j.jfluidstructs.2015.08.007).

Record type: Article

Abstract

Digital Image Correlation (DIC) is employed for the measurement of full-field deformation during fluid-structure interaction experiments in a wind tunnel. The methodology developed for the wind tunnel environment is quantitatively assessed. The static deformation error of the system is shown to be less than 0.8% when applied to a curved aerofoil specimen moved through known displacements using a micrometer. Enclosed camera fairings were shown to be required to minimise error due to wind induced camera vibration under aerodynamic loading. The methodology was demonstrated using a high performance curved foil, from a NACRA F20 sailing catamaran, tested within the University of Southampton RJ Mitchell, 3.5m x 2.4m, wind tunnel. The aerodynamic forces induced in the wind tunnel are relatively small, compared with typical hydrodynamic loading, resulting in small deformations. The coupled deflection and blade twist is evaluated over the tip region (80-100% Span, measured from the root) for a range of wind speeds and angles of attack. Steady deformations at low angles of attack were shown to be well captured however unsteady deformations at higher angles of attack were observed as an increase in variability due to hardware limitations in the current DIC system. It is concluded that higher DIC sample rates are required to assess unsteady deformations in the future. The full field deformation data reveals limited blade twist for low angles of attack, below the stall angle. For larger angles, however, there is a tendency to reduce the effective angle of attack at the tip of the structure, combined with an unsteady structural response. This capability highlights the benefits of the presented methodology over fixed-point measurements as the three dimensional foil deflections can be assessed over a large tip region. In addition, the methodology demonstrates that very small deformations and twist angles can be resolved.

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Submitted date: 18 December 2014
Accepted/In Press date: 19 August 2015
e-pub ahead of print date: 19 September 2015
Published date: October 2015
Keywords: wind tunnel tests, digital image correlation, fluid structures interaction, composite materials, aeroelastic tailoring
Organisations: Fluid Structure Interactions Group

Identifiers

Local EPrints ID: 384146
URI: http://eprints.soton.ac.uk/id/eprint/384146
ISSN: 0889-9746
PURE UUID: 202998c9-b124-46e4-b380-3f92cd5d9e5e
ORCID for Joseph Banks: ORCID iD orcid.org/0000-0002-3777-8962
ORCID for Stephen Turnock: ORCID iD orcid.org/0000-0001-6288-0400

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Date deposited: 18 Nov 2015 13:39
Last modified: 26 Nov 2019 02:06

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Author: Joseph Banks ORCID iD
Author: Xavier Soubeyran
Author: Stephen Turnock ORCID iD
Author: Stephen Boyd

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