APPLIED PHYSICS: Streams Traced by Speckle

Science  02 Jun 2006:
Vol. 312, Issue 5778, pp. 1279b
DOI: 10.1126/science.312.5778.1279b

Particle-imaging velocimetry (PIV), a common technique for studying the flow of fluids, involves seeding a fluid with tracer particles such as dyes or photoluminescent beads, and then tracking their motion over time. In many applications, there is a growing need to understand the flow pattern in all three spatial dimensions. However, the optics involved in PIV generally limit the sampling volume to a thin two-dimensional (2D) sheet within the bulk flowing system.

Alaimo et al. present a simple technique to address this shortcoming. After directing a coherent probe beam through the flowing particle suspension, they detect and analyze the speckle pattern that results from the interference of the weak portion of light scattered by the seed particles with the intense transmitted portion. Because the speckle pattern arises from particles distributed throughout the whole fluid volume, 3D flow dynamics can be extracted from the 2D velocity mapping data acquired in real time. The authors demonstrate the method using an aqueous suspension of 300-nm-diameter latex spheres. — ISO

Appl. Phys. Lett. 88, 191101 (2006).

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