Two-color particle-imaging velocimetry using a single argon-ion laser |
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Authors: | M E Post D D Trump L P Goss R D Hancock |
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Institution: | (1) Systems Research Laboratories, Inc., A Division of Arvin/Calspan, 2800 Indian Ripple Road, 45440-3696 Dayton, OH, USA;(2) Aero Propulsion and Power Directorate, Wright Laboratory, Wright-Patterson Air Force Base, 45433-7103, OH, USA |
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Abstract: | A swept-beam, two-color particle-imaging velocimetry (PIV) technique has been developed which utilizes a single argon-ion laser for illuminating the seed particles in a flowfield. In previous two-color PIV techniques two pulsed lasers were employed as the different-color light sources. In the present experiment the particles in a two-dimensional shear-layer flow were illuminated using arotating mirror to sweep the 488.0-nm (blue) and 514·5-nm (green) lines of the argon-ion laser through a test section. The blue- and greenparticle positions were recorded on color film with a 35-mm camera. The unique color coding eliminates the directional ambiguities associated with single-color techniques because the order in which the particle images are produced is known. Analysis of these two-color PIV images involved digitizing the exposed film to obtain the blue and green-particle image fields and processing the digitized images with velocity-displacement software. Argon-ion lasers are available in many laboratories; with the addition of a rotating mirror and a few optical components, it is possible to conduct flow-visualization experiments and make quantitative velocity measurements in many flow facilities.List of symbols
d
length of displacement vector
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d
m
distance between rotating mirror and concave mirror
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n
f
number of facets on rotating mirror
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R
seed-particle radius
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v
velocity in x, y plane
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v
s
sweep velocity of laser beams, assumed to be in y direction from top to bottom of field of view
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v
x, v
y, v
z
x, y, and z components of velocity
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x
1, y
1
color-1 particle coordinates
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x
2, y
2
color-2 particle coordinates
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y
max
y dimension of field of view, assumed to be the long dimension
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s
spatial separation of beams as they approach rotating mirror
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t
time separation of laser sheets or of swept beams passing fixed point
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t
b
time between successive sweeps through test section by same beam
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t
s
time required for both beams to sweep through test section
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angular separation of beams reflecting from rotating mirror
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fluid viscosity
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v
angular velocity of rotating mirror in cycles per second
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seed-particle density
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seed-particle response time
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v,
d,
t
standard deviation of velocity, displacement, and time
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vorticity
This work was supported, in part, by the Aero Propulsion and Power Directorate of Wright Laboratory under Contract No. F33615-90-C-2033. |
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Keywords: | |
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