A numerical and experimental investigation of the effects of combination of spur dikes in series on a flow field

Abstract

Spur dikes are used to protect river banks from erosion and also keep the main mitigation channel. Different additional structures such as “collar” and “protective spur dike” are used for reducing scouring around spur dikes. The combination of spur dike in series may be a new method to decrease scouring without using any additional structures. A computational fluid dynamic model was developed to investigate flow characteristics around triple combinational series with different shapes of spur dike (I (simple)-, L- and T-shaped). In order to verify the numerical model a (T L I) combinational series was experimented in the laboratory, and hydraulic characteristics of flow around them were measured. In this research, the numerical simulation based on optimum combination and control test is used in FLOW-3D software for analyses. In addition, several turbulence models (k–e, RNG and LES) have been applied to achieve the best numerical simulation. The results showed that the largest flow speed, pressure, shear stress and turbulent energy in the flat bed formed close to the location of maximum scour depth and erosion. Reduction in these features helps decrease scouring and erosion. The combination of spur dike in series is a method which achieves this goal. The (L T T) series is the most effective in reducing speed, shear stress, pressure and turbulent energy around spur dikes. Actually, different geometries of spur dike, when used together, have positive effect on reducing scouring. Finally, combination of spur dikes with protective spur dike compared with series without protect. The result showed that protective spur dike can decrease intensity of flow characteristics and scour depth.