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TECHNICAL PAPERS

Laser-Doppler Measurements of Velocities Just Downstream of a Collapsible Tube During Flow-Induced Oscillations

[+] Author and Article Information
C. D. Bertram, G. Diaz de Tuesta, A. H. Nugent

Graduate School of Biomedical Engineering, University of New South Wales, Sydney, Australia 2052

J Biomech Eng 123(5), 493-499 (May 16, 2001) (7 pages) doi:10.1115/1.1388294 History: Received March 07, 2000; Revised May 16, 2001
Copyright © 2001 by ASME
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References

Figures

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Cross section of the downstream end of the pressure chamber, showing the laser probe with crossed beams intersecting in the flow lumen just downstream of the everted clamped end of the silicone rubber tube. The laser beams pass through the transparent octagon.
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An example of particle velocities and simultaneous pressure samples recorded at one location, together with the times of pressure threshold detection (full-height vertical dotted lines intersecting the pressure trace), before ensemble-averaging. The threshold was detected in the analog trace of which this is an irregularly sampled digital representation. One of the cycles is shown divided into the 16 equal time bins (short dotted lines).
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First experimental series: u(y, z) at the time bins 16t/T =2, 4, 8, 12, 14, 16 through the ensemble-averaged cycle. The measured grid was half as dense in y and z as the interpolated grid shown, which passes through all measured points.
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(a) The (u, v) vector profiles on the diameter corresponding to the major axis of the collapsed tube. All 16 time bins are shown, with time through the cycle increasing upward. The (equal) scale of both ordinate and abscissa is m/s; the separation of the origins of adjacent vectors is Δy=0.5 mm. (b) The corresponding (u, w) vector profiles along 0z, the minor axis of the collapsed tube.
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Second experimental series: u(y, z) at 16t/T=2, 4, 8, 12, 14, 16 as taken from the experiments in which u(t) and w(t) were measured, with one interpolated point between each pair of measurements.
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(a) The (u, v) vector profiles along 0y, i.e., along the major axis of the tube collapse cross section. The (equal) scale of both ordinate and abscissa is m/s; the separation of the origins of adjacent vectors is Δy=0.75 mm. (b) The corresponding (u, w) vector profiles along 0z, the minor axis of the collapsed tube. Note scale change from panel (a).
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Secondary flow (v, w) vectors at 16t/T=2, 4, 8, 12, 14, 16 from the second-series experiments. The vectors are shown as matchsticks, with the head as the point of the more usual arrow, and the tail showing the location of measurement. Position in the (y, z) plane is normalized by tube diameter.
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The overlaid-cycles u component data for one location from the second-series experiments. This location (x=3.55, y =−2.25, z=0.75 mm) gave rise also to the data shown in Fig. 2. The absence of data at u∼0 is inherent to laser-Doppler anemometry.
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The power spectral density of the interpolated data for both u (solid line) and v (dotted line), from the first-series location x=2.65, y=−1.50, z=4.47 mm. The added straight line has slope −5/3.

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