Traveling of Oscillating Vortices and Its Thermal Effects in a Bending Channel

Abstract

Driven by the periodical reverse of flow orientation, vortices in oscillatory flow induce a local high-speed and low-pressure flow region near the wall, which brings complex physical phenomena to viscous dissipation and heat transfer. This research focuses on the above-mentioned features by relating Spatio-temporal relationships between fluid dynamics and energy transmission. A two-dimensional oscillation model working in a thermoacoustic resonator is developed, considering heating and cooling processes in bending channels. We address oscillatory vortices' formation and transmission process in the bending channel. The acoustic streaming velocity field is obtained by postprocessing and proved to be the primary mechanism to induce spatial vortices in the vicinity of the entrance. The transferring vortices caused by the bending channel are like mini-pumps occupying fluid regions, which contribute to the local enhanced heat transfer performance and are influenced by the wall boundary conditions. The result also shows that skin friction in bending channels occupies about 10%–30% of total resistance, and the driving ratio is more sensitive to viscous dissipation than the wavy height of the bending channel. This study provides an approach to understanding the underlying mechanisms of heat transfer enhancement from hydrodynamics and inspiration to design compact heat exchangers employed in the oscillating flow.