On the use of lattice Boltzmann model for simulating dean flow of non-Newtonian fluids in curved square ducts

In the present work, the effect of a fluid’s shear-thinning and extension-hardening behavior is investigated on its flow characteristics in a typical curved square duct using a three-dimensional 27-velocities (D3Q27) incompressible lattice Boltzmann model. The main objective of the work is to examine how a fluid’s non-Newtonian viscous behavior affects the onset of Dean instability (i.e., the sudden shift from a two-cell to a four-cell vortex structure) in a curved square duct. The fluid of interest is assumed to obey Pinho’s rheological model in which shear-thinning and extension-hardening are both represented by a single power-law equation. It is found that shear-thinning has a stabilizing effect on the flow. On the other hand, extension-hardening is found to destabilize the flow.

► The lattice Boltzmann method (LBM) is well capable of simulating Dean instability of non-Newtonian fluids.
► Shear-thinning has a stabilizing effect on the Dean instability.
► Extension-hardening has a destabilizing effect on the Dean instability.