Author(s): Ahmad Shakibaeinia; Amir Reza Zarrati; Mohamed Reza Majdzadeh Tabatabaei
Linked Author(s): Amir Reza Zarrati, Ahmad Shakibaeinia
Keywords: River channel confluence; Three-dimensional modeling; Flow structure; Bed topography; SSIIM
Abstract: River channel confluence is one of the features of each river system. The point, at which two channels meet, is marked by highly complex three-dimensional pattern of flow, sediment transport and bed changes. Complex flow characteristics within a confluence is dominated by distinctive secondary currents, flow deflection, flow separation, flow contraction and water surface variations which are mainly dependent on confluence angle and discharge ratio. Furthermore in natural rivers flow structure is affected by morphological features such as bed variations in the confluence. Therefore, in river confluence studies, bed topography should be taken into account. Large numbers of research works have been conducted, but a comprehensive threedimensional numerical study of the confluence flow characteristics under different angles, discharge ratios considering bed changes has not been reported yet. In the present work, SSIIM which is a three-dimensional numerical model is applied to predict flow pattern and bed topography under wide range of natural conditions. The model solves Reynolds equations using finite volume method coupled with an advance turbulent model, it also has the capability of computing water surface elevation. The numerical model was first validated using available confluence experimental and field data and then was applied to a confluence with different angles and discharge ratios. Obtained Results illustrate that flow and bed topography in a confluence is affected by a vortex system due to flow deflection, separation and three counter-rotating helical cells. Besides scour depth and deposition size, the main topographical features, are highly influenced by confluence angle and discharge ratio.
Year: 2007