Studies on Dispersion and Turbulence in Liquid Flows

Abstract

<p>This thesis describes an experimental study of the dispersion and turbulence of Newtonian fluids and dilute aqueous solutions of a drag reducing polymer, Reten 423, when ejected from a thin wall slot or point source into either developing or fully developed turbulent internal water flow at relatively high Reynolds numbers.</p> <p>Two small water tunnels with injection facilities were constructed in which concentration and energy spectra measurements were made using a spectrophotometer and a Laser Doppler Anemometer. The investigation was carried out with a maximum flow velocity of the order of 4.5 m/s for various injection flow rates and with injection concentrations in the range 0 to 1000 w.p.p.m.</p> <p>It was found that the dispersion rate for polymer solutions is reduced when compared to Newtonian diffusion. It was also observed that the velocity profiles for developing flows with polymer injection are fuller than those for water alone. Furthermore, there was no noticeable change in energy spectrum for low polymer concentration. However, for high injection concentration there was an increase of the energy within the low frequency end of the spectrum and a reduction of energy for the high frequency end of the spectrum.</p> <p>Correlations for the concentration profiles, diffusion boundary layer growth, maximum concentration and eddy diffusivity are presented. The results indicate that a universal diffusion correlation exists which represents the data for both Newtonian and polymer solutions.</p> <p>A very interesting phenomenon was observed for hetrogeneous polymer flow fields in which the sampling rate had an effect on the measured polymer solution concentration. The apparent concentration on the measured concentration approached the correct value when the sampling velocity approached that for the main stream, i.e. the isokinetic condition. This phenomenon is important and should be taken into consideration, for example, when using sampling techniques to obtain concentration profiles in nonhomogeneous polymer solution flow fields.</p>