Jet flows in non-Newtonian fluids

Abstract

Plane and axisymmetric, laminar, submerged jet flows of non-Newtonian power-law fluids, issuing from an orifice in a wall, are investigated for large Reynolds numbers. In contrast to previous investigations,the interaction between the jet flow and the induced flow is taken into account using matched asymptotic expansions combined with a two-scaling technique. The following four effects, occuring at sufficiently low values of the power-law index, are analyzed:• Very large mass entrainment into the jet.• Non-negligible viscosity in the induced outer flow.• Slow, but substantial, variation of the momentum flow in the jet with increasing distance from the orifice. • Spreading of the jet into a recirculatory flow (eddy). The analytical results are compared with experimental data taken from the literature. For the purpose of further comparisons, and in order to extend the investigation into flow regimes where the asymptotic expansion ceases to be valid, the full equations of motion are solved numerically by means of a finite element code. Mathematics Subject Classification (2000). 35Q30, 35Q35, 41A60, 65Z05, 76D05, 76D09, 76D10, 76D25.

Measurement and analysis of flow of concentrated fiber suspensions through a 2‐D sudden expansion using UVP

“…This implies that the theoretical Newtonian laminar flow model cannot capture the flow properties of pulp suspensions in this regime. Furthermore, the change in fluid properties due to changes in concentration or velocity also implies that no similarity solution is valid in the laminar flow regime as also found in non‐Newtonian fluids …”

“…They also showed that for yield stress exhibiting fluids no similarity profiles ever develop in the far‐field region of the flow‐field. Stehr and Schneider investigated non‐Newtonian planar and asymmetric power law jet flows with a numerical finite element method at a low Reynolds number. From their simulations they concluded that the classical boundary layer theory was invalid for lower values of the power law index, n < ⅔, due to the change in the momentum flow in the jet.…”