AN INVESTIGATION OF VELOCITY PROFILES IN THE LAMINAR SUBLAYER WITH NON-NEWTONIAN ADDITIVES USING HIGH SPEED PHOTOMICROSCOPY.
Final technical rept. Sep 65-May 69,
MASSACHUSETTS UNIV AMHERST ENGINEERING RESEARCH INST
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The report describes the development of a high speed photomicroscopic technique, using dark-field microscopy, for the measurement of turbulent velocity distributions in a circular pipe. The method is especially adapted to velocity measurements extremely close to a boundary, of the order of five microns. Velocities are obtained from the analysis of 16 mm film exposure with a high speed camera, due to the motion of illuminated polystyrene tracers, 1.305 microns in diameter, dispersed in distilled water and aqueous solutions of non-Newtonian additives. An electronic flash time base is used to synchronize absolute and relative motion for a permanent record on the film. The photomicroscopic method was used to determine velocity distributions of distilled water and aqueous solutions of the non-Newtonian additives Polyox-301, CMC, and Polyhall-27, flowing in a circular lucite channel 5030 microns in diameter, at a Reynolds number of 4,000. Additive concentrations of 1100 and 110 by weight were used. The results for distilled water indicate excellent agreement with the postulated linear velocity distribution for flow in the laminar sublayer. Polyox-301 at both concentrations displayed a marked increase in the laminar sublayer thickness, as determined by the slope of the laminar sublayer velocity profile, while CMC and Polyhall-27 showed little deviation with distilled water. A quantitative description of the laminar sublayer structure with and without additives is also incorporated. Author
- Fluid Mechanics