Reynolds number effect on the dissipation function in wall-bounded flows

The evolution with Reynolds number of the dissipation function, normalized by wall variables, is investigated using direct numerical simulation (DNS) databases for incompressible turbulent Poiseuille flow in a plane channel, at friction Reynolds numbers up to Re-tau=2000. DNS results show that the mean part, directly dissipated by the mean flow, reaches a constant value while the turbulent part, converted into turbulent kinetic energy before being dissipated, follows a logarithmic law. This result shows that the logarithmic law of friction can be obtained without any assumption on the mean velocity distribution. The proposed law is in good agreement with experimental results in plane-channel and boundary layer flows. (c) 2007 American Institute of Physics.