Large-Eddy simulation of turbulent pipe flow of power-law fluids

摘要

Fully developed turbulent flows of power-law fluids in a cylindrical stationary pipe are investigated numerically by the use of large eddy simulation (LES) for various power law index (0.5 <= n <= 1.4) at different Reynolds numbers (4000 <= Re-s <= 12,000). To validate the present computations, the predictions are compared to the results reported in the archival literature for laminar and turbulent flows. The LES predictions agree reasonably favourably with the findings of the literature. The log-region of the mean axial velocity profile expands with increasing Re-s and decreasing power-law index n. The predicted friction factor for n <= 1 at Re-s = 4000 is slightly overestimated in comparison with Dodge and Metzner correlation, and is better interpolated by Comes correlation. With increasing n the apparent viscosity increases close to the wall and decreases for y(+) > 30. This implies that the turbulent fluctuations develop and are more intense further from the wall when n > 1 and closer to the wall when n < 1. The influence of Re-s and n on the higher-order statistics (skewness and flatness) is analyzed. Visualizations of the instantaneous filtered velocity fields exhibit turbulent patterns which develop more as n increases. (C) 2015 Elsevier Inc. All rights reserved.