2-D Particle Image Velocimetry (PIV)
PIV (Particle Image Velocimetry) is one of the promising method to measure a particular velocity field on the plane that using a laser light sheet and a camera.
Particles, such as smoke, can be added to a flow to trace the fluid motion. It is possible illuminate the particles with a sheet of laser light in order to visualize a slice of a complicated fluid flow pattern. Assuming that the particles faithfully follow the streamlines of the flow, we can not only visualize the flow but also measure its velocity using the particle image velocimetry with a cross correlation method.
The advantage of this quantitative visualization method is measuring all flow field not a point measurement such as hot-wire and pitot tube techniques and it is also a non-contact measurement method.
3-D Stereoscopic PIV Measurement
(i=1,2, j=1,2,3, c=1,2)
Laser Induced Fluorescence (LIF)
Laser Induced Fluorescence(LIF) is the method that measure an instantaneous concentration field in turbulent flow cross-section. This technique is using the dyes that is emitted a fluorescent light when absorbing a light. Rhodamine B is a representative dye for the LIF method that is emitted a fluorescent light in the water when absorbing the wavelength range from 532nm from Nd: Yag laser. We can detect concentration field on the plane by proper calibration. The following the formular is the relationship between the incident light intensity, concentration and the fluorescence intensity.
Here, If means the brightness of detected light from the camera, Φ, I0, ε, c, represent the quantum efficiency, the luminance of the incident light, the absorption through path length, and the concentration of dye, respectively.
PIV / LIF Simultaneous Measurement
Particle image velocimetry and laser induced fluorescence method can measure velocity field and concentration field simultaneously. It's possible if instruments (laser, PIV and LIF cameras) are synchronized by a synchronizer. It shows valuable information about the characteristics of the mixing and turbulent structures in the mixing tank.