Improvement of drag reduction prediction in viscoelastic pipe flows using proper low-Reynolds k-ε turbulence models

Developing proper turbulence models in order to predict flow characteristics of viscoelastic drag-reducing fluids has become as a considerable portion of non-Newtonian flows researches. In this numerical study, three different low-Reynolds-number k-ε models namely, Launder–Sharma, Lam–Bremhorst and Malin are used based on the adopted viscoelastic turbulence closure of Cruz et al. (2004). Simulation results for friction factor, mean axial velocity, turbulent kinetic energy and Reynolds shear stress are obtained for three aqueous polymer solutions (0.3% carboxymethyl cellulose, 0.2% xanthan gum and 0.2% polyacrylamide) and validated against the corresponding experimental data. While a good agreement exists for the bulk parameters like drag reduction (DR) or, equivalently, the friction factor, some discrepancies are observed in other simulation results of turbulence characteristics, in particular for situations with higher DR levels. The Malin’s model which accounts for the shear-thinning property of the polymeric solutions, leads to the closest results for carboxymethyl cellulose and xanthan gum cases, while for polyacrylamide with the lowest power index n, the friction factor is larger than other simulation results and an increasing difference from the experimental data is observed.