Experimental Study of the Effects of Skew Angle on Flow Field in Skewed Compound Channels with Inclined Floodplains

During a flood, water flows out of the main channel and enters the floodplains. In nature, due to the influence of local topographic conditions, rivers have often irregular and non-prismatic shape. In non-prismatic compound channels, because of the effect of changing in cross-sectional area along the channel, the flow structure is more complex than prismatic compound channels. Therefore, it is important to study the flow characteristics in such channels and it can help researcher to better understand the flow behavior in rivers, especially during floods. In the present study, the flow characteristics in a compound channel with inclined and skew floodplains has been investigated experimentally. The experiments were performed at three relative depths of 0.2, 0.3 and 0.4 and for two skew angles of 11.31° and 3.81°. The water surface profile, lateral distributions of velocity and boundary shear stress along the skew part of the flume have been measured and reported. The results of experiments indicate that the lateral distributions of velocity and boundary shear stress in skewed compound channels with inclined floodplains are non-uniform and asymmetric. Also, the flow velocity and boundary shear stress in diverging floodplain are always higher than its value in converging floodplain. By increasing the skew angle of the floodplains from 3.81 to 11.31 degrees, the boundary shear stress and flow velocity in the main channel and on the floodplains increase.