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Download or read book Direct Numerical Simulation of Turbulent Drag Reduction: Molecular Modeling Molecular Optimization and Modeling Without Consititutive Equations written by and published by . This book was released on 2003 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present numerical simulations of turbulent drag reduction in wall-bounded flows by additives. The bulk of the work concentrates on polymer additives. A multiscale approach was used to study the fine details of polymer dynamics in turbulence and the transfer of energy between polymers and turbulence. It was shown that polymers extract energy from near-wall vortices and release energy in high-speed streaks very close to the wall. We derived a conceptual model which applies to the two, statistically distinct regimes of polymer drag reduction, namely low drag reduction (LDR) and high drag reduction (HDR). Another additive, fibres, was found to obey to a different mechanism which requires close interaction of multiple vortices.