Coaxial volumetric velocimetry

Journal Article (2018)
Author(s)

JFG Schneiders (TU Delft - Aerodynamics)

F. Scarano (TU Delft - Flow Physics and Technology)

C. Jux (TU Delft - Aerodynamics)

A Sciacchitano (TU Delft - Aerodynamics)

Department
Flow Physics and Technology
Copyright
© 2018 J.F.G. Schneiders, F. Scarano, C. Jux, A. Sciacchitano
DOI related publication
https://doi.org/10.1088/1361-6501/aab07d
More Info
expand_more
Publication Year
2018
Language
English
Copyright
© 2018 J.F.G. Schneiders, F. Scarano, C. Jux, A. Sciacchitano
Department
Flow Physics and Technology
Bibliographical Note
Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. @en
Issue number
6
Volume number
29
Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Abstract

This study describes the working principles of the coaxial volumetric velocimeter (CVV) for wind tunnel measurements. The measurement system is derived from the concept of tomographic PIV in combination with recent developments of Lagrangian particle tracking. The main characteristic of the CVV is its small tomographic aperture and the coaxial arrangement between the illumination and imaging directions. The system consists of a multi-camera arrangement subtending only few degrees solid angle and a long focal depth. Contrary to established PIV practice, laser illumination is provided along the same direction as that of the camera views, reducing the optical access requirements to a single viewing direction. The laser light is expanded to illuminate the full field of view of the cameras. Such illumination and imaging conditions along a deep measurement volume dictate the use of tracer particles with a large scattering area. In the present work, helium-filled soap bubbles are used. The fundamental principles of the CVV in terms of dynamic velocity and spatial range are discussed. Maximum particle image density is shown to limit tracer particle seeding concentration and instantaneous spatial resolution. Time-averaged flow fields can be obtained at high spatial resolution by ensemble averaging. The use of the CVV for time-averaged measurements is demonstrated in two wind tunnel experiments. After comparing the CVV measurements with the potential flow in front of a sphere, the near-surface flow around a complex wind tunnel model of a cyclist is measured. The measurements yield the volumetric time-averaged velocity and vorticity field. The measurements of the streamlines in proximity of the surface give an indication of the skin-friction lines pattern, which is of use in the interpretation of the surface flow topology.

Files

Schneiders_2018_Meas._Sci._Tec... (pdf)
(pdf | 4.11 Mb)
- Embargo expired in 11-06-2021
License info not available