FLUID VELOCITY MEASUREMENT BY DOPPLER SHIFT OF SCATTERED LIGHT.
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMICAL ENGINEERING
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The report describes the laser Doppler velocimeter, and the design necessary to study turbulent flow of liquids where the spatial resolution required is 10 to 50 micrometers. For the lower limit it is necessary to use diffraction limited optics, to match the refractive indices of the pipe and the liquid, and for the beams to enter and leave the pipe normally. For a glass pipe containing water, 60 micrometers is the best resolution obtainable. Much higher powered lasers are needed if dissolved polymer is the scatterer, than if particles are used. Errors occur due to the velocity gradient in the scattering element, and to the finite included angles of the incident and scattered beams. Author
- Test Facilities, Equipment and Methods
- Fluid Mechanics