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Two-color particle-imaging velocimetry using a single argon-ion laser


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.

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d :

length of displacement vector

d m :

distance between rotating mirror and concave mirror

n f :

number of facets on rotating mirror

R :

seed-particle radius

v :

velocity in x, y plane

v s :

sweep velocity of laser beams, assumed to be in y direction from top to bottom of field of view

v x, v y, v z :

x, y, and z components of velocity

x 1, y 1 :

color-1 particle coordinates

x 2, y 2 :

color-2 particle coordinates

y max :

y dimension of field of view, assumed to be the long dimension

Δs :

spatial separation of beams as they approach rotating mirror

Δt :

time separation of laser sheets or of swept beams passing fixed point

Δt b :

time between successive sweeps through test section by same beam

Δt s :

time required for both beams to sweep through test section

Δθ :

angular separation of beams reflecting from rotating mirror

μ :

fluid viscosity

v :

angular velocity of rotating mirror in cycles per second

ϱ :

seed-particle density

τ :

seed-particle response time

σ v, σ d, σ t :

standard deviation of velocity, displacement, and time

ω :



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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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Post, M.E., Trump, D.D., Goss, L.P. et al. Two-color particle-imaging velocimetry using a single argon-ion laser. Experiments in Fluids 16, 263–272 (1994).

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  • Pulse Laser
  • Test Section
  • Velocity Measurement
  • Particle Image
  • Velocimetry