Enhancement of heat and mass transfer in a microchannel via passive oscillation of a flexible vortex generator

The advantages of both the passive and active heat and mass transfer enhancement techniques are used. A beam (rigid or flexible) as vortex generator (VG) is placed downstream of a cylindrical obstacle on the lower wall of a microchannel. The governing equations are solved using ALE approach. The elastic beam oscillates due to the forces exerted by the periodic flow behind the obstacle on it leading to the formation and separation of periodic vortices from the tip of the beam. These vortices disrupt the thermal boundary layer and prevent it from re-growing and hence increase the heat transfer rate dramatically. The total Nu number increases 18.46%, the Darcy friction factor experiences a decrease of 42.33%, the thermal performance factor increases 42% and the mixing index increases 16.86% with respect to the rigid beam case. Finally, the flexible beam used here would not experience failure in the laminar flow regime. (C) 2019 Elsevier Ltd. All rights reserved.