Abstract

In using particle-image velocimetry (PIV) to obtain an instantaneous two-dimensional velocity map in a fluid flow, a double-exposure photograph of the seeded medium is analyzed optically to produce correlation fringes. In an earlier paper we showed theoretically that the signal-to-noise ratio of these fringes, and hence measurement accuracy, is significantly improved by using a two-step photographic process. In this paper, experimental results are presented that support the previous theoretical work and reveal the great potential of PIV in experimental fluid mechanics.

© 1985 Optical Society of America

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References

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  1. C. J. D. Pickering, N. A. Halliwell, “Particle image velocimetry: Improving fringe signal-to-noise with a two-step photographic process,” J. Opt. Soc. Am. A. 2, 610–615 (1985).
    [CrossRef]
  2. T. D. Dudderar, P. G. Simpkins, “Laser speckle photography in a fluid medium,” Nature (London) 270, 45–46 (1977).
    [CrossRef]
  3. J. M. Burch, J. M. J. Tokarski, “Production of multiple beam fringes from photographic scatterers,” Opt. Acta 15, 101–111 (1968).
  4. C. J. D. Pickering, N. A. Halliwell, “Speckle photography in fluid flows: signal recovery with two-step processing,” Appl. Opt. 23, 1128–1129 (1984).
    [CrossRef] [PubMed]
  5. C. J. D. Pickering, N. A. Halliwell, “Laser speckle photography and particle image velocimetry: photographic film noise,” Appl. Opt. 23, 2961–2969 (1984).
    [CrossRef] [PubMed]
  6. D. W. Robinson, “Automatic fringe analysis with a computer image-processing system,” Appl. Opt. 22, 2169–2175 (1984).
    [CrossRef]
  7. R. Meynart, “Instantaneous velocity field measurements in unsteady gas flow by speckle velocimetry,” Appl. Opt. 22, 535–540 (1983).
    [CrossRef] [PubMed]

1985

C. J. D. Pickering, N. A. Halliwell, “Particle image velocimetry: Improving fringe signal-to-noise with a two-step photographic process,” J. Opt. Soc. Am. A. 2, 610–615 (1985).
[CrossRef]

1984

1983

1977

T. D. Dudderar, P. G. Simpkins, “Laser speckle photography in a fluid medium,” Nature (London) 270, 45–46 (1977).
[CrossRef]

1968

J. M. Burch, J. M. J. Tokarski, “Production of multiple beam fringes from photographic scatterers,” Opt. Acta 15, 101–111 (1968).

Burch, J. M.

J. M. Burch, J. M. J. Tokarski, “Production of multiple beam fringes from photographic scatterers,” Opt. Acta 15, 101–111 (1968).

Dudderar, T. D.

T. D. Dudderar, P. G. Simpkins, “Laser speckle photography in a fluid medium,” Nature (London) 270, 45–46 (1977).
[CrossRef]

Halliwell, N. A.

Meynart, R.

Pickering, C. J. D.

Robinson, D. W.

Simpkins, P. G.

T. D. Dudderar, P. G. Simpkins, “Laser speckle photography in a fluid medium,” Nature (London) 270, 45–46 (1977).
[CrossRef]

Tokarski, J. M. J.

J. M. Burch, J. M. J. Tokarski, “Production of multiple beam fringes from photographic scatterers,” Opt. Acta 15, 101–111 (1968).

Appl. Opt.

J. Opt. Soc. Am. A.

C. J. D. Pickering, N. A. Halliwell, “Particle image velocimetry: Improving fringe signal-to-noise with a two-step photographic process,” J. Opt. Soc. Am. A. 2, 610–615 (1985).
[CrossRef]

Nature (London)

T. D. Dudderar, P. G. Simpkins, “Laser speckle photography in a fluid medium,” Nature (London) 270, 45–46 (1977).
[CrossRef]

Opt. Acta

J. M. Burch, J. M. J. Tokarski, “Production of multiple beam fringes from photographic scatterers,” Opt. Acta 15, 101–111 (1968).

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Figures (4)

Fig. 1
Fig. 1

Optical measurement system.

Fig. 2
Fig. 2

Fringe analysis.

Fig. 3
Fig. 3

Fringe patterns and their Fourier spectra: (a) original negative, (b) copied positive.

Fig. 4
Fig. 4

Improvement in fringe SNR by two-step processing—experimental results.

Equations (2)

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W ( β ) = SNR c ( β ) SNR 0 ( β ) ( β 0 )
η = V ( 1 Δ X ) 3 ,

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