A new method for characterizing turbulent mixing in semiconcentrated suspensions, TAPPI JOURNAL November 2011

Please Note: This document will be available in PDF format in the "My Electronic Documents" link on the home page once your order has been completed. Please make sure you have the latest version of Acrobat Reader. Click on the Acrobat Reader icon to check for the latest version, it’s FREE. To print a hardcopy of a PDF file correctly you must have a postscript printer. If you are not sure if your printer is a postscript printer please refer to your owner’s manual.

Purchase of electronic (downloadable) documents made at www.tappi.org by credit cards, followed by instant download CANNOT be cancelled. We do not offer refunds on electronic download documents.

ABSTRACT: A high-frequency conductivity probe was used in conjunction with advanced signal processing to measure the turbulent fluctuations of a passive scalar, namely a saline solution, injected into semiconcentrated, monodispersed suspensions consisting of either 2-mm rayon fibers or 130-µm microspheres. The probe was mounted in a pipe flow so that its radial position could be adjusted manually. A saline solution was injected into the centerline of the pipe at a specified velocity relative to the suspension flow. The mean conductivity signal gathered with this tool enabled estimation of the local concentration of salt at a given point in the flow, i.e., the mean spatial dispersion of the dosed component. Further analysis of the high-frequency fluctuating signal enables characterization of the local mixing energy and turbulent spectrum, i.e., the spectral mixing scales available in the suspensions under a given set of conditions.

Application: Producers of paper and board products are given new insights into minimizing unwanted variabili-ty in paper properties that may result from poor mixing of stock components, uneven addition of chemical additives, or dilution of the thick stock prior to the headbox.