Heat Dependent Thermo-Viscous Shear-Thinning Fluid Flowing around a Double-Sphere Configuration within a Pipe

Kurzfassung

Non-Newtonian fluid properties can change the flow behaviour and the resulting flow topology significantly, even for low Reynolds number laminar flows. The prediction of the flow field is even more difficult when thermal effects come into play. In particular when high shear rates occur and temperature is changing the fluid properties, unexpected flow phenomena can be observed. Focal point of this study is the laminar pipe flow of a thermo-viscous shear thinning Carreau fluid around double-sphere configurations. The two spheres are arranged in-line in pipe axial direction. In dependence of the distance between the spheres the flow topology around the sphere pair changes. The non-isothermal non-newtonian shear-thinnning fluid flows reveal temperature dependent deflections of the wake flow. Complicated flow separation and attachment structures between and behind the spheres occur. In the present CFD study sphere-wall temperature-dependent flow-structures are investigated. The temperature dependence of the fluid viscosity is modelled by applying the standard Williams-Landel-Ferry equation. It is shown that thermal-viscous shear thinning due to high shear rates and heat transfer from the sphere walls leads to a significant decrease of viscosity of three orders of magnitude in the near-field of the spheres. The locally reduced viscosity can be used to control the flow around the double sphere flow configuration. In the present simulation campaign thermal boundary conditions are varied over a wide range in order to derive relations between heat transfer, non-newtonian fluid properties and the behaviour of the double-sphere flow.