LES of Turbulent Flow of The Non-Newtonian Fluid: The Turbulence Statistics

TL;DR

This study uses LES with an extended Smagorinsky model to analyze the turbulence characteristics of shear thinning non-Newtonian fluids in a pipe, comparing results with experimental and DNS data to evaluate the influence of rheology.

Contribution

It provides a detailed numerical investigation of non-Newtonian turbulence using LES, highlighting the effects of shear thinning behavior on turbulence statistics and energy transport.

Findings

Velocity fluctuations originate near the wall and transfer radially.

Turbulent kinetic energy is enhanced in the radial direction.

Energy transfer between flow layers is suppressed compared to Newtonian fluids.

Abstract

A large eddy simulation (LES) with an extended Smagorinsky model has been carried to investigate numerically the fully developed turbulent flow of a shear thinning fluid (n=0.75) in a stationary pipe at a simulation's Reynolds number equals to 4000 with a grid resolution of 65 3 gridpoints in axial, radial and circumferential directions and a domain length of 20R. The present study set out to critically evaluate the influence of the Non-Newtonian rheological and hydrodynamic behaviour on the turbulence main features, as well as to ascertain the accuracy and reliability of the laboratory code predicted results. The turbulent flow statistics obtained compared reasonably well with the experimental data and DNS results. A reasonably good agreement has been obtained between the predicted results and available results of literature. The main findings suggest that the mean axial velocity fluctuations were generated in the wall vicinity and transferred to the radial and spanwise components, which resulted in to an enhancement in the kinetic energy of turbulent fluctuations along the radial direction. The energy transport from the axial fluctuations to the other fluctuations components between the flow layers was suppressed compared to that of the Newtonian fluid.