La Vision

Laser Doppler Velocimetry (LDV) is a technique that allows velocity measurement at a point in a flow field with a high temporal resolution. In this technique the fluid is illuminated by a laser beam and then the scattered light in the particles in the fluid is collected and processed.



In the practice, two laser beams resultant from one simple beam laser of same intensity are focused at a same point in a flow field. A standard interference is formed where the intersection of the laser beams occurs defining a region whose volume is known. The moving particles spread up the light which is collected by a photo detector.

The resultant exit frequency of the photo detector is directly related to the velocity of the particle. If two additional laser beams with different wavelengths are focused to the same volume measure, two, and even three velocity components can be determined simultaneously.

Typically, the blue and green lines, or blue, green, and violet lines from the ion argon laser are used to measure the multicomponents. If only one of the laser beams, in each pair, had a frequency change, the LDV System can also measure the flow reversions.

Applications

Measures of rotor tip vortex (Three Component Laser Doppler Velocimetry);
Measures in boundary layer;
Surveys in the region of the mat;
Measures of draining in shock tube.

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