Experimentelle Untersuchungen zum Austrag von Gasblasen und Feststoffteilchen aus der Str�mung viskoelastischer Fl�ssigkeiten vor Lochblenden

Kärmer, R.; Reher, E.-O.

doi:10.1007/bf01534278

Cited by 1 publication

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“…Karnis et a]., 1963Karnis, 1966Karnis & Mason, 1966Gauthier et al, 1971bKarnis, 1966Highgate & Whorlow, 1969Gauthier et al, 1971aBartram, 1973., Highgate, 1966Highgate & Whorlow, 1968Highgate & Whorlow, 1969Walker, 1965Giesekus, 1969Karmer & Reher, 1978 Laboratory for Computer Science, MIT), an advanced computer language for symbolic manipulation.…”

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confidence: 99%

Lateral migration of a rigid sphere in torsional flow of a viscoelastic fluid

1984

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A single polystyrene sphere of radius a, between 141 and 275 micron, when injected into a disk-plate (torsional) flow of polybutene (viscosity 36 poise, M,, -680), migrates radially inward at a rate that is dramatically increased by dissolving 1% of a high-molecular-weight polyisobutylene ( M , -los) to make the fluid viscoelastic. The torsional flow field was created by rotating a 21-cm-diameter disk at a rate w of 6-9 rpm with a gap H of 3.7-5.4 mm between this and a ground glass pilate with the fluid in the gap. Lateral migration toward a lower shear rate increased with increasing shear rate and with increasing shear rate gradient in the manner predicted by Brunn (1976) or Chan and Leal (1977). Shear rates up to 25 s -.~ were investigated. Below a shear rate of 8 s-l the radial migration velocity is of the form v, = -L ( w a / W r , where L is a positive constant containing the fluid properties, and r is the radial position of the particle. T. E. KARIS, D. C. PRIEVE and S. L. ROSEN Department of Chemical EngineeringCarnegie-Mellon University Pittsburgh, PA 15213 SCOPEDuring nonhomogeneous shear flow of a viscoelastic fluid, a rigid particle entrained by the fluid will migrate across the streamlines, even in the absence of external forces such as gravity or an electric field. Such migration affects the efficiency of capture of particles by grains of fibers in deep-bed or fibrous mat filters. Migration of additives or gel Darticles during ex-trusion of polymer melts might also be responsible for a phenomenon called "plate-out," which eventually leads to plugging of the die.In this paper, we report direct visual observation of migration of a single spherical particle across the streamlines of torsional flow of a 1% w/w solution of a high-molecular-weight polyisobutylene in a low-molecular-weight polybutene solvent. The radial migration of the sphere is measured at different positions in the flow field for two different rotation speeds w, two different plate separations H, and three different particle radii a.In a later paper we will report on the effect of fluid properties. CONCLUSIONS AND SIGNIFICANCEExcept near the outer boundary of the rotating disk, the migration was always observed to occur in the direction of decreasing shear rate. For local shear rates less than 8 s-1, the radial speed v, was observed to be within 20% of -v, = L(wa/ Wr, where L = 0.027 s for this fluid. The form of this equation was deduced from the more general theory developed by Brunn (1976) and Chan and Leal (1977). Further, we observed no significant dependence of the migration speed on the vertical position of the particle between the horizontal plates.

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