Effect of rotation and cross thermal buoyancy on the nanofluidic transport around a circular cylinder

Abstract

We numerically explore the coupled effect of a primary free stream nanofluid flow and secondary induced flows due to rotation and thermal buoyancy around a rotating and heated circular cylinder. The free stream flow of the Cu–H2O nanofluid is considered for a Reynolds number range 10≤Re≤30. The solid fraction (Cu-nanoparticles) varies in the base fluid (H2O) in the range 0%≤φ≤10%. The rotation and thermal buoyancy induced flows are considered for the range of dimensionless rotational speed, 0≤Ω≤3, and Richardson number, 0≤Ri<5. We estimate the first and the second critical rotational speeds characterizing the complete suppression of the steady and unsteady wakes. We also demonstrate a second vortex shedding mode originated at high rotational speeds. Furthermore, this study determines the critical thermal buoyancy to initiate the vortex shedding. The critical buoyancy parameter is found to increase with the increasing rotation rate and decrease with the increasing Reynolds number. However, it drops, rises, or remains constant depending on the solid fraction present in the base fluid.