Software simulation of submerged vane effects on scour depth at channel confluence

The Channels and rivers confluence phenomenon is the issue which happens in the irrigation and drainage channels, superficial water accumulative channels, water and waste water refinery and rivers. The aim of this research is to investigate the effect of several installed submerged vanes in tributary channel on controlling and decreasing the erosion at 90 degrees confluence of channels, detecting the best situation and vanes orders by using the simulation software. In this research, Flow-3D flow simulation software was used to model the various states of submerged vanes at 90-degree channels confluence. In order to verify the results, the data from the experiments carried out in the laboratory of the civil engineering department of Sharif University of Technology have been used. The experimental model consists of a main channel with a length of 12 meters and a width of 40 cm and a tributary channel of 3 meters in length, the width of the tributary channel is equal to the main channel. The tributary channel is located 6.35 meters from the beginning of the main channel and is connected to the main channel at a 90-degree angle. The using equations were Navier-Stokes and continuity equations for modeling incompressible flows. For modeling Turbulence, the k-w equation model was used. The results of this study showed that software simulation can estimate the scour pattern very well. So the difference between the maximum depth of scour of numerical and laboratory models in confluence was 1.4%. Also few modeling were done with angles, dimensions and different locations of vanes to calculate the best conditions of vanes to decrease the depth of scour in channels confluence. The results show that it is possible to decrease the scour hole dimensions, considering that submerged vanes are installed in the 60 degree (in respect to longitudinal axis of channel), the ratio of the length of the submerged vanes to the channel width is equal to 0.25, the longitudinal spacing of the submerged vanes is half the width of the channel, the spacing of the submerged vanes from each other is 0.375 of the channel width and the distance between the installation of the submerged vanes from the intersection of 0.25 to 0.375 is the width of the channel; submerged vanes effectively reduce the maximum depth of scour hole at the junction of two channels with a 90 degree angle. The final result of this study shows that if submerged vanes are installed in an appropriate position with optimal dimension in the tributary channel, they can reduce the maximum depth of the scour hole at channel confluences. In this study, the maximum scour depth was reduced by 21% submerged vanes compared to non submerged vanes.