Numerical Simulation of Dead Zone Flows in an Open Channel with a Side Cavity and Sudden Enlargement.

Three–dimensional numerical simulation is carried out to study the fundamental properties of flows in an open channel with a dead zone. In this paper, the flow field in two types of dead zone have been studied: one is rectangular side cavity and another one is the dead zone created at the downstream of channel with width enchroachment (i.e. sudden enlarged zone). A non-linear k- model is employed using finite volume method with a curvilinear coordinate system. It is 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. With increasing the length of the cavity, the circulation pattern and their numbers are changed along with velocity magnitude. For the open channel with sudden enlargment, although the upstream arrangemnet of flow domain is same as the cavity flow, the flow in the enlarged zone has the freedom to flow towards downstream in logitudinal direction. Due to this free downstream, the simulated flow field in the sudden enlarged zone is 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.