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Updated: Jun 20, 2026

Simultaneous Measurement of Turbulence and Particle Kinematics Using Flow Imaging Techniques
Published on: March 12, 2019
Velocimetry in laminar and turbulent flows using the photothermal deflection effect with a transient grating
Abstract:
An enhanced-precision, high-signal method for velocity measurements with photothermal deflection spectroscopy is presented. A transient refractive-index grating is formed by the interference of two pulsed, pump-laser beams in an absorbing gas. The motion of the grating is detected by the oscillatory deflection of a probe beam, which has a diameter smaller than the fringe spacing. This two-beam pump improves on single-beam pumps because there are more markers for the velocity determination, and the larger thermal gradients increase the probe deflection. The method is illustrated by velocity maps in a laminar ethylene/nitrogen jet using a CO(2) pump laser. Velocity distributions and noise levels were also measured with grid-induced turbulence above the jet.
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