On the connection between Kolmogorov microscales and friction in pipe flows of viscoplastic fluids

The present work extends Kolmogorov's micro-scales to a large family of viscoplastic fluids. The new micro-scales, combined with Gioia and Chakaborty's (2006) friction phenomenology theory, lead to a unified framework for the description of the friction coefficient in turbulent flows. A resulting Blasius-type friction equation is tested against some available experimental data and shows good agreement over a significant range of Hedstrom and Reynolds numbers. The work also comments on the role of the new expression as a possible benchmark test for the convergence of DNS simulations. The formula also provides limits for the maximum drag reduction of viscoplastic flows.