Inertial thermal convection in a suddenly expanding viscoplastic flow field

Abstract

Inertial thermal convection from recirculating and non-recirculating flows of viscoplastic fluids through an axisymmetric 1:5 sudden expansion has been studied. The governing mass and fully-elliptic partial differential equations of motion and energy along with the Bingham constitutive equation were numerically solved to provide accurate predictions of the flow and thermal fields. A parametric study is implemented to study the impact of geometry, inertia, rheology, and thermo-physical properties on the thermal structure of suddenly expanding, non-isothermal, viscoplastic flows. Detailed visualizations of the velocity, viscosity, and temperature fields demonstrate the dramatic impact of yield stress presence on both the flow and thermal behavior. Furthermore, transitioning from a recirculating flow field to a non-recirculating viscoplastic flow field, within the present geometry, dramatically influences the thermal characteristics of the viscoplastic flow field. Recirculating suddenly expanding viscoplastic flows are characterized by two local compressions in the thermal boundary layer, upstream and downstream of the impingement region. However, non-recirculating viscoplastic flows display only one local compression in the thermal boundary layer, immediately downstream of the large, ramp-like, stagnant corner region.