Near wake flow and forced convection heat transfer of sinusoidal wavy cylinder based on flow decomposition

Based on flow decomposition we investigate the near wake flow and forced convection heat transfer around sinusoidal wavy cylinders, with an attempt to deepen our understanding of inherent correlations between near wake flow and heat transfer/transport. Large eddy simulations (LES) are conducted at a Prandtl number Pr = 0.7 and a subcritical Reynolds number Re = 3.0 x103 for the unsteady flow of the sinusoidal wavy cylinder of different wavelengths lambda(= 1.89, 3.79 and 6.06Dm) and a fixed wave amplitude alpha (= 0.152Dm), where Dm is the mean diameter of the cylinder. The near wake flow of the wavy cylinder, together with heat transport, is decomposed via the traditional triple decomposition and a newly-proposed quadruple decomposition, taking into account dominant periodic vortex shedding and/or spanwise heterogeneity of the flow. While heat transfer from the surface of the wavy cylinder to the surrounding flow is distinctly different from that of the smooth cylinder, results from the flow decomposition reveal intrinsic characteristics of the near wake flow and heat transport for the wavy cylinder with different wavelengths. It is observed that heat transport in the near wake of the wavy cylinder is predominantly associated with the coherent spanwise vortices of dominant shedding frequency as well as the spanwise time-invariant components of the mean flow. It is also found that the major contributor to Reynolds stresses (heat flux) is the temporal random stresses (temporal random heat flux) in the near wake of the wavy cylinder. Furthermore, results from the quadruple decomposition show that the spanwise-averaged heat flux in the near wake of the smooth cylinder and the wavy cylinder with.= 1.89D m encompassesboth spatiotemporal random and temporal dispersive heat fluxes outside the recirculation bubble and only the former heat flux inside the recirculation bubble. However, the spanwiseaveraged heat flux in the near wake of the wavy cylinder with.= 3.79 or 6.06D m is profoundly and exclusively contributed by the spatial dispersive heat flux outside the recirculation bubble. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Based on flow decomposition, this study investigates the near wake flow and forced convection heat transfer around sinusoidal wavy cylinders, aiming to deepen the understanding of the relationship between near wake flow and heat transfer. Large eddy simulations are conducted for different wavelengths of the wavy cylinders, revealing intrinsic characteristics of the near wake flow and heat transport. The results show that heat transport in the near wake is mainly associated with coherent spanwise vortices and the temporal random stresses. Moreover, the contributions of spatiotemporal random and temporal dispersive heat fluxes are analyzed in the near wake of different wavy cylinders.