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Effect of drag reducers on transport phenomena in turbulent pipe flow

Authors

  • Peter J. Hamersma,

    1. University of Amsterdam, Dept. of Chemical Engineering, 1018 WV Amsterdam, The Netherlands
    Current affiliation:
    1. Delft University of Technology, Faculty of Applied Sciences, Julianalaan 136, 2628 BL Delft, The Netherlands
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  • Jan M. H. Fortuin

    Corresponding author
    1. University of Amsterdam, Dept. of Chemical Engineering, 1018 WV Amsterdam, The Netherlands
    • University of Amsterdam, Dept. of Chemical Engineering, 1018 WV Amsterdam, The Netherlands
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Abstract

Momentum transfer in turbulent pipe flows (d = 51 mm) with and without a drag reducer was studied. Age distributions of coherent fluid structures at the pipe wall were determined at different Reynolds numbers (104<Re<6 × 104) using laser-Doppler velocimetry (LDV) and a suitable discriminating procedure. Mean ages, mean transfer thicknesses, friction factors, and time-averaged axial velocity profiles derived from LDV signals were compared with those from axial pressure gradients using the random surface-renewal model. The distribution of the ages was random, and drag reducers increased the mean age and the mean transfer thickness of the fluid elements at the wall, thus decreasing momentum and heat transfer at the fluid–wall interface. The mechanism of single-surface renewals was derived from conditionally averaged, local axial fluid velocities obtained from LDV signals.

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