MEASUREMENT OF LAMINAR VELOCITY PROFILES WITH NON-NEWTONIAN ADDITIVES USING PHOTOMICROSCOPY.
MASSACHUSETTS UNIV AMHERST FLUID MECHANICS LAB
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The report describes the development of a photomicroscopic technique, using dark field microscopy, for the direct measurement of velocity distribution in an essentially one-dimensional channel. The method is particularly adapted to velocity measurements in close proximity to a frictional boundary, of the order of five microns. Velocities are obtained from the analysis of light streaks, obtained from photomicrographs, due to the motion of illuminated polystyrene tracers, 0.55 microns in diameter, dispersed in distilled water and aqueous solutions of a number of non-Newtonian additives. Time intervals between light streak patterns were obtained by means of a specially constructed light interrupter mechanism rather than reliance upon the camera shutter speed. The photomicroscopic method was used to determine vertical velocity distributions of distilled water and aqueous solutions of the non-Newtonian additives CMC, Polyox 301 and Polyhall 27, flowing in a lucite channel 13 mm. wide and 1.5 mm in depth, at channel Reynolds numbers of 0.92. Concentrations of the additives of 18 and 14 by weight were used. The results for distilled water indicate nearly perfect agreement with the theoretical parabolic velocity distribution for flow between parallel flat plates. The additives at both concentrations showed little variation with distilled water except near the boundaries, from 0 to 100 microns, where the velocity was noticeably greater, in some cases by a factor of two. Author
- Fluid Mechanics