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Unformatted text preview: shift, in the frequency of the scattered light. The shift f is proportional to the velocity of the particle. There is essentially zero disturbance of the flow by the laser.
Figure 6.29h shows the popular dual-beam mode of the LDA. A focusing device
splits the laser into two beams, which cross the flow at an angle . Their intersection, | e-Text Main Menu | Textbook Table of Contents | Study Guide Chapter 6 Viscous Flow in Ducts which is the measuring volume or resolution of the measurement, resembles an ellipsoid about 0.5 mm wide and 0.1 mm in diameter. Particles passing through this measuring volume scatter the beams; they then pass through receiving optics to a photodetector which converts the light to an electric signal. A signal processor then converts
electric frequency to a voltage which can be either displayed or stored. If is the wavelength of the laser light, the measured velocity is given by
2 sin ( /2) V (6.119) Multiple components of velocity can be detected by using more than...
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This note was uploaded on 10/27/2009 for the course MAE 101a taught by Professor Sakar during the Spring '08 term at UCSD.
- Spring '08