Characteristics of the forced convection of heat in wavy channels under a transitional flow regime: a numerical study

Esfandiary, Mohsen, Saedodin, Seyfolah and Karimi, Nader (2025) Characteristics of the forced convection of heat in wavy channels under a transitional flow regime: a numerical study. Physics of Fluids, 37, [067137]. (doi:10.1063/5.0269938).

Abstract

Forced convection in wavy conduits under transitional flow regimes remains largely unexplored. This study numerically investigates the flow characteristics of a fully out-of-phase sinusoidal wavy channel across a broad range of Reynolds number. A refined large eddy simulation framework, incorporating an adjustable implicit filtering based on turbulence kinetic energy evolution, is employed to enhance resolution and capture flow dynamics accurately. The results reveal that heat transfer rate and skin friction enhancements are strongly correlated with the Reynolds number, primarily driven by the intermittent disruption of the boundary layer and flow transition induced by secondary flow instabilities. A comparison with a straight channel under similar conditions revealed a slight enhancement in Nu—defined based on the channel's average height— accompanied by a minimal pressure loss in the laminar flows. In contrast, in turbulent flows both Nu and pressure drop enhancements are significant, limiting the practical applicability of wavy channels under these conditions. Notably, the optimal case in the transitional regime (Re = 500) features a Nu enhancement comparable to turbulent flows while maintaining a pressure drop like that of laminar flows, highlighting the potential advantages of operating in this regime. An evaluation of the thermal efficiency factor, which accounts for both Nu and pressure loss, reveals that wavy channels outperform straight channels by 37% at Re = 500. This advantage diminished for Re < 300 and became less pronounced at Re > 500. These findings show that transitional flow regimes can enhance heat convection in wavy channels, balancing thermal efficiency and pressure drop.

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Contributors

Author: Nader Karimi

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