1 research outputs found
Thermal convection of viscoelastic fluids in concentric rotating cylinders: Elastic turbulence and kinetic energy budget analysis
The introduction of solid polymers into a Newtonian solvent induces
significant modifications in the flow behavior and heat transfer
characteristics of resulting viscoelastic fluids. This study performs a
comprehensive numerical investigation on thermal convection within a system
comprising two concentric horizontal cylinders filled with viscoelastic fluids,
with the inner cylinder rotating. The analysis encompasses all three modes of
thermal convection, namely, forced, free, and mixed convection, over a range of
Weissenberg numbers up to 10 and three values of the Richardson number, namely,
0, 0.143, and , representing forced, mixed, and free convection modes
of heat transfer, respectively. In forced convection, the flow field remains
stable, while in free and mixed convection, an increase in the Weissenberg
number leads to a transition from steady to unsteady periodic, quasi-periodic,
and finally, an aperiodic and chaotic behavior. This transition arises due to
the presence of elastic instability and the subsequent appearance of elastic
turbulence in viscoelastic fluids with the increasing Weissenberg number.
Furthermore, our findings indicate that fluid viscoelasticity has minimal
influence on heat transfer rates in the cases of forced and free convection.
Conversely, heat transfer rates in mixed convection increase with the
Weissenberg number. We conduct a detailed analysis of the viscoelastic kinetic
energy budget to elucidate this enhancement in the heat transfer rate for
viscoelastic fluids. We show that this improved heat transfer results from
kinetic energy transfer from polymer molecules to the flow field, leading to
increased chaotic motion within the system and, eventually, higher heat
transfer rates