  Fluid-structure interaction (FSI) of thin flexible fins coupled with
convective heat transfer has applications in energy harvesting and in
understanding functioning of several biological systems. We numerically
investigate FSI of the thin flexible fins involving large-scale flow-induced
deformation as a potential heat transfer enhancement technique. An in-house,
strongly-coupled fluid-structure interaction (FSI) solver is employed in which
flow and structure solvers are based on sharp-interface immersed boundary and
finite element method, respectively. We consider twin flexible fins in a heated
channel with laminar pulsating cross flow. The vortex ring past the fin sweep
higher sources of vorticity generated on the channel walls out into the
downstream - promoting the mixing of the fluid. The moving fin assists in
convective mixing, augmenting convection in bulk and at the walls; and thereby
reducing thermal boundary layer thickness and improving heat transfer at the
channel walls. The thermal augmentation is quantified in term of instantaneous
Nusselt number at the wall. Results are presented for two limiting cases of
thermal conductivity of the fin - an insulated fin and a highly conductive fin.
We discuss feasibility of flexible fins and effect of flow cycle-to-cycle
variation on the Nusselt number. Finally, we investigate the effect of
important problem parameters - Young's Modulus, flow frequency and Prandtl
number - on the thermal augmentation.
