Simulation of Dead Zone Flows in an Open Channel with Secondary Currents.

In this paper, the fundamental properties of flows in an open channel with a dead zone was studied through the three–dimensional numerical simulation using two types of dead zones: one was rectangular side cavity and another one was the dead zone created at the downstream of channel with width enchroachment (i.e. sudden enlarged zone). A non-linear k- model was employed using finite volume method with a curvilinear coordinate system. It was found that the flow in the side cavity is characterized by three types of flow phenomena: the circulation inside the dead-zone, periodic coherent vortices at the interface of main stream and dead zone, and the water surface oscillation inside the dead zone. In this study all these characteristics are successfully reproduced by numerical simulation. The time averaged flow properties and temporal change of velocity profiles are well compared with previous experimental results. The flow exchanges between mainstream and dead zone was observed in the secondary flow field. For the open channel with sudden enlargment, due to the free downstream, the simulated flow field in the sudden enlarged zone was found to be significantly different than that of open channel flows with side cavity. Beside the academic interests, present study contributes to understand the developement, extent and behaviour of flows in a dead zone for proper managemnet of river system and other water courses.