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Usage of body-fitted windows in PIV image processing

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conference contribution
posted on 10.07.2018 by Matthew Ward, Adrian Spencer, Martin Passmore
Flow close to the boundaries of bodies is often difficult to measure using particle image velocimetry (PIV); factors such as glare, velocity gradients and the body itself all present challenges in obtaining good quality results. One common problem in conventional PIV algorithms is that they are based on square grids, which for most applications is not aligned with the shape of the body. This means the body will clip part of the window resulting in fewer particles and erroneously placed vectors. Being able to align the interrogation window shape to the body boundary would remove these sources of error. This study investigates the effect that applying non-square windows has, compared to conventional square windows for three test cases: a free-field, a circular body and an airfoil shape. For each of these a number of interrogation methods are tested. For the circular body, conventional and rotated square windows were tested along with a body fitted mesh. The image was also deformed into R-θ coordinates to enable conventional square window processing, before de-warping the vector field. Square, rotated square and body fitted techniques were also tested on an airfoil shape. It was found that the body-fitted and warping methods both showed significant improvements in the boundary layer over the square meshes; although the warping process added computational expense. The meshing technique was found to have little impact on the free field as there was no body or velocity gradient. Utilising this interrogation method in conjunction with developed methods of automated edge detection and more mature processing algorithms will result in better measurements close to bodies than is possible with conventional square windows. An example application of this technique on flow around a sphere is also demonstrated.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Aeronautical and Automotive Engineering

Published in

International Symposium on Applications of Laser Techniques to Fluid Mechanics

Citation

WARD, M., SPENCER, A. and PASSMORE, M.A., 2018. Usage of body-fitted windows in PIV image processing. IN: Proceedings of the 19th International Symposium on Applications of Laser and Imaging Techniques to Fluid Mechanics, Lisbon, Portugal, 16-19 July 2018.

Publisher

© LISBON Simposia

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Acceptance date

01/06/2018

Publication date

2018

Notes

This is a conference paper.

Language

en

Location

Lisbon, Portugal

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