Diffusion of Drag Reducing Aqueous Polymer Solutions in External Flow

Abstract

<p>This thesis describes an experimental study of the diffusion of dilute squeous drag reducing polymers when ejected from a thin wall slot into a developing turbulent boundary layer (external flow).</p> <p>A horizontal flat plate located in a 0.1524 m. (6 in.) I.D. plexiglass pipe was specifically designed for obtaining diffusion data. Water or aqueous polymer solutions which were dyed with a fluorescing dye were injected tangentially into the boundary layer through a slot situated near the leading edge of the flat plate. Samples were taken from the flow field and by using a spectrophotometer, concentration profiles were established. The investigation was carried out for a constant free stream velocity of 5.4 m./sec. for various injection flow rates and concentrations in the range 0 to 1500 w.p.p.m.</p> <p>It was found that the diffusion rate will increase for very low polymer concentrations (of the order of 0.75 w.p.p.m.), while the diffusion rate will be reduced for higher concentrations. The resulting data have been compared to Newtonian diffusion phenomena as well as the available data for polymer additives.</p> <p>Correlations for the concentration profiles, diffusion boundary Layer growth, wall concentration and eddy diffusivity are presented. The research covers the four important zones of diffusion with emphasis on the earlier developing zones for which there are virtually no data available. The results indicate that a universal diffusion correlation exists which represents the data for both Newtonian and polymer solutions for the far region downstream but indicate decidedly different phenomena near the injection region, confirming a previously published theoretical analysis.</p>