An experimental study of the turbulent mixing layer in concentrated fiber suspensions.
Artikel i vetenskaplig tidskrift, 2012

Turbulence structures in a free mixing layer after a backward-facing step were studied in concentrated pulp suspensions (0.5-3% by weight) using Laser Doppler Anemometry (LDA) at two predetermined average inflow velocities (0.9 and 1.8 m/s). Both average and fluctuating velocities were investigated and the findings were compared with measurements in water. The experimental findings show that both the average velocities and the RMS velocities in the mixing layer decreased with an increase in concentration. Furthermore, by analyzing the energy spectra at the center of the mixing layer, it was possible to extract the inertial sub-range of pulp suspensions with a concentration of 0.5% at the lower inflow velocity and in suspensions up to a concentration of 1% at the higher inflow velocity. At higher concentrations the turbulence was damped by the fiber network and no turbulence structures could be extracted. The energy content at lower frequencies was higher in the pulp suspensions than in the experiments in pure water.

LDA

Turbulence

Mixing layer

Fiber suspension

Författare

Julia Claesson

Chalmers, Kemi- och bioteknik, Kemisk apparatteknik

Tomas Wikström

Unknown organization

Anders Rasmuson

Chalmers, Kemi- och bioteknik, Kemisk apparatteknik

Wallenberg Wood Science Center (WWSC)

Nordic Pulp and Paper Research Journal

0283-2631 (ISSN)

Vol. 27 5 940-946

Styrkeområden

Produktion

Energi

Ämneskategorier

Kemiteknik