Forced convection heat transfer around a circular cylinder in laminar flow: An insight from Lagrangian coherent structures

The Lagrangian coherent structure (LCS) method is introduced to the convection heat transfer problem, and the forced convection heat transfer around a circular cylinder in laminar flow regime is analyzed from the Lagrangian viewpoint. First, the mechanics model of forced convection heat transfer around a circular cylinder is introduced along with the mathematical formulations. Subsequently, an implicit flow solver based on the characteristic-based split finite element method and the dual-stepping method is proposed to solve the flow and heat transfer equations, and the computation of LCS employing the finite-time Lyapunov exponent is discussed in detail. The accuracy and stability of the flow solver are examined carefully utilizing the data reported in the literature, and the grid-independence test is conducted. Finally, the mass and energy transport features around the circular cylinder at Pr (Prandtl number) = 0.7 and Re (Reynolds number) = 20-180 are investigated by relating the instantaneous thermal and vorticity patterns, lift coefficient, drag coefficient, and Nusselt number to the LCSs in the flow field. The results obtained may improve the existing understanding of forced convection heat transfer around a circular cylinder and pave the road for the application of LCSs in convection heat transfer problems.