Large-eddy simulation of Carreau fluid flow over a circular cylinder at a sub-critical Reynolds number

Non-Newtonian fluid flow over a circular cylinder at a sub-critical Reynolds number Re=3900 is investigated with large-eddy simulation. Behaviors of both shear-thinning and shear-thickening fluids are compared with the Newtonian fluid flow at the nominal Re. Carreau fluids are chosen here to study non-Newtonian fluid flow. The shear-dependent viscosity changes flow separation point on the cylinder and laminar-to-turbulent transition in separating shear layer. Apparently, low viscosity in shear-thinning fluid causes early flow separation and turbulent transition, resulting in large pressure drag and flow fluctuation indicated by the lift rms. In contrast, shear-thickening fluid exhibits delayed flow separation and turbulent transition, leading to large viscous drag and reduced flow fluctuation. Such non-Newtonian behaviors are comparable to the Newtonian fluid flow in the sub-critical regime but at different apparent Reynolds numbers. The current non-Newtonian fluids modify the apparent Reynolds number by a factor of about 2–3.5. As the apparent Reynolds numbers still belong to the sub-critical regime, the drag coefficient varies little. A notable difference is observed for the lift rms that varies more than double in the shear-thinning fluid.