CFD-based estimation and experiments on the loss coefficient for Bingham and power-law fluids through diffusers and elbows

• The non-Newtonian flow in diffusers and elbows of different geometries are studied.
• Loss coefficients are reported for power-law and Bingham fluid for pipeline fittings.
• The flow field is computed with CFD technique validated by measurements.
• The performance of turbulence models for non-Newtonian fluids is studied.

This paper presents results on the CFD-based estimation of loss coefficients for typical pipeline elements in the case of Bingham and power law fluids. The actual elements are diffusers with angles between 7.5° and 40° and elbows of R/DR/D ratios between 1 and 10. Three fluids were studied; water (for validation purposes), a power-law fluid (0.13 m/m% Carbopol 971 solution) and Bingham plastic fluids with Hedström number varying from 10 to 106106. Experiments were conducted with water and power-law fluid to validate the CFD computations. Loss coefficients are given for the Reynolds number regime that is usual in engineering applications. The behavior of different turbulence models (eddy-viscosity and Reynolds stress models) are also reported.