Simulation of flow profile response to alternate bar formation in rivers

Abstract

Alternate bars are common in alluvial rivers. The formation of alternate bars is derived from the instability of flow and sediment in the channel. The formation of the alternate bars causes the changes in hydrodynamics condition in the channel. This study presents the analysis on the impact of alternate bar formation on the characteristic of flow in the channel. The objective of the study is to investigate the effect of alternate bars on the flow distribution. The study was observed through 2D computer simulation analysis by using Nays2DH solver in iRIC software. The length and width of the channel used were 12 and 0.5 m, respectively. The channel bed was initially set to be flat. The discharge was kept constant with different sediment sizes. The study found that the direction of the velocity of water was diverted away from the alternate bars after these bars were formed. Furthermore, the variation of sediment size does not majorly affect the conditions of the alternate bar; thus not also affected the flow profile. However, the velocity was progressively increased from upstream to downstream in the channel with a bigger size of bed material. Additionally, the velocity also was higher at the center but lowered on both sides of the channel. The profiles of velocity were mainly parallel with the bed level, where the velocity was higher as the bed level increased.