| Abstract [eng] |
Mixing of fluids plays an important role in engineering applications, especially heat transfer. Recent experimental study showed that when three parallel flows mix behind obstacles, most rapid mixing is obtained when the flows are of different regimes. The purpose of this work is to investigate the underlying dynamics of vortices as three flows mix, and therefore multiple RANS and LES calculations were carried out. Slowest, as well as three fastest cases were modeled substantially well with RANS, whereas the three cases in the middle were not. In all successfully modeled cases usual Karman vortex streets form, although they bend more and get disturbed as inlet velocity increases. It was found that vortex streets in the slowest inlet velocity case (the one with fastest mixing) exhibits a symmetric in-phase regime, whereas all other cases have asymmetric flip-flop regime, with anti-phase configuration dominating in the fastest ones. This work points out that fast mixing in slowest inlet case is perhaps not because flow regimes in three channels are different, but possibly due to symmetric in-phase vortex shedding regime behind the obstacles. To check this hypothesis, we suggest to repeat experiments in recent study with the same flow regimes yet with narrower obstacles to avoid asymmetric vortex shedding. |
