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Seventh International Symposium on Turbulence and Shear Flow Phenomena
July, 28-31, 2011, Ottawa Convention Centre, Ottawa, Canada

DOI: 10.1615/TSFP7

NUMERICAL EXPERIMENTS ON SELF-CONTROL OF WALL TURBULENCE BY SURFACE MORPHOLOGY

pages 1-6
DOI: 10.1615/TSFP7.1930
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ABSTRACT

The self-control of turbulence in wall-bounded flows is considered in pipes of non-circular cross-sections which act to restructure fluctuations towards the limiting state where these must be entirely suppressed. Direct numerical simulations of turbulence in pipes of polygon-shaped cross-sections with straight and profiled sides were performed at a Reynolds number Reτ ~ 300 based on the wall shear velocity and the hydraulic diameter. Using the lattice Boltzmann numerical algorithm, turbulence was resolved with up to about 540 × 106 grid points (8192 × 257 × 256 in the x1, x2 and x3 directions). The first exploratory results show a decrease in the viscous drag around corners, resulting in a reduction of the skin-friction coefficient compared with expectations based on the well-established concept of hydraulic diameter and the use of the Blasius correlation. These findings support the conjecture that turbulence might be completely suppressed if the pipe cross-section is a polygon consisting of a sufficient number of profiled sides of the same length which intersect at right-angles at the corners.

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