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Proceedings Paper

Fundamental limitations to the spatial resolution and flow volume that can be mapped using holographic particle image velocimetry
Author(s): Jeremy M. Coupland; Julia Lobera Salazar; Neil A. Halliwell
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Paper Abstract

We have recently proposed a variant of holographic particle image velocimetry (HPIV) to measure three-component measurements of fluid velocity throughout an extended flow volume. In essence the technique uses double exposure holography to record the positions of seeding particles at two, close spaced constants in time. Analysis of the resulting record is achieved by computing the auto (or cross) correlation of the complex amplitude distributions transmitted by a sampling aperture placed within a real, reconstruction of the holographic image. IN the case of sparsely seeded flows, it is straightforward to show that the field transmitted by the aperture is dominated by the particle images reconstructed close to the aperture itself and the measurement is therefore attributed to the instantaneous flow velocity at the centre of the aperture. As the seeding concentration is increased, however, a significant contribution of the transmitted field is due to light scattered from more distant particles. If significant velocity gradients exist, the contribution due to distant particles is largely un- correlated and the local particle displacement can be extracted even if the field is dominated by this component. If a significant proportion of the scattered light that passes from the aperture is collected from areas in the flow with similar velocity (for example from stagnant regions or light scattered from the flow vessel) then spurious peaks can occur in the correlation signal. This paper examines the limitations on the flow volume that can be mapped at a given seeding concentration and hence the fundamental limits on the number of velocity measurements that can be retrieved from a single recording.

Paper Details

Date Published: 31 August 2000
PDF: 12 pages
Proc. SPIE 4076, Optical Diagnostics for Industrial Applications, (31 August 2000); doi: 10.1117/12.397966
Show Author Affiliations
Jeremy M. Coupland, Loughborough Univ. (United Kingdom)
Julia Lobera Salazar, Univ. of Zaragoza (Spain)
Neil A. Halliwell, Loughborough Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 4076:
Optical Diagnostics for Industrial Applications
Neil A. Halliwell, Editor(s)

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