원형 실린더가 주기적으로 배열된 채널 유동의 이차 불안정성

초록

A parametric study has been carried out to elucidate the secondary instability of channel flow with a streamwise-periodic array of cylinders. This flow configuration is relevant to heat exchanger applications. the presence of cylinders in channel flow causes the attached wall boundary layer to separate, leading to significant change in flow instabilities. There exist two kinds of instabilities; flow undergoes a primary instability(Hopf bifurcation) at a lower Reynolds number, and the unsteady two-dimensional flow becomes unstable to three-dimensional disturbances at a higher Reynolds number(secondary instability). We carry out Floquet stability analysis of the time periodic unsteady flow to find critical Reynolds number and the most unstable spanwise wave number for the secondary instability, depending on the distance between the cylinder and the channel wall. The three-dimensional structure of the most dominant mode is also discussed.