Numerical simulation of the transition of a Newtonian fluid to a viscoplastic state in a turbulent flow

The non-isothermal turbulent flow and transition to a viscoplastic state of high-viscosity oil with physical and chemical properties depending on fluid temperature is numerically studied. The turbulence of fluid flow in a pipe is described using the Reynolds stress, Reynolds algebraic stress, and two-parameter isotropic models. The simulations show the boundaries of the region of the manifestation of Newtonian behavior and fluid transition to a viscoplastic state. The Reynolds stress model and the algebraic Reynolds stress model show significant anisotropy in the velocity fluctuation profiles of Newtonian and non-Newtonian fluids. The shift of the locus of maximal magnitudes of turbulent pulsations, Reynolds stress, and turbulent kinetic energy towards a flow core region is observed. The height of the zone with a completely stopped fluid is predicted and determined numerically. The appearance of a stagnation zone near the wall causes a significant decrease in wall friction and heat transfer due to a decrease in the environment temperature. & COPY; 2022 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).