Abstract
The spacing of spur dikes is an important consideration for the layout of spur dike channels. This study focuses on the local scour morphology and flow field characteristics of spur dikes with different spacings. The results show that the maximum scour depth is generally found in the vicinity of the first spur dike head. With the increase of the spacing of spur dikes, the shielding effect of the first spur dike is weakened. The maximum velocity in the main flow zone is twice that of the approach flow velocity in the fixed bed. But it is approximately the same as the incoming velocity in equilibrium scouring. The maximum turbulent energy appears to be mainly located in the backflow area of the fourth spur dike in the fixed bed, while the maximum value appears at the second spur dike head in the movable bed. Further, the shear stress decreases as scouring develops. Pearson correlation analysis was carried out between scour depth and shear stress. The analysis results are significantly correlated, indicating that the bed shear stress plays a prominent role in the scouring process. These discoveries can serve as a guide to determine the most reasonable spacing of spur dikes.
Highlights
Investigation of the local scour and flow field around spur dikes has a long history and remains a significant research focus area
Cs,i ρi where Cs,i is the suspended sediment mass concentration, which is defined as the sediment mass per volume of fluid-sediment mixture, us,i is the sediment velocity of species, D is the diffusivity, and u is the bulk velocity of the fluid-sediment mixture, which is obtained by solving the continuity and Navier–Stokes equations with a turbulence closure model
The area with the maximum turbulent energy appeared at the junction of the high-velocity main flow area and the backflow area between spur dikes, especially in the backflow area of spur dike IV in the fixed bed
Summary
Investigation of the local scour and flow field around spur dikes has a long history and remains a significant research focus area. Pandey et al [7] concluded that the maximum scour depth always develops on the upstream side of the first spur dike. Considering the maximum scour depth and erosion volume, 4l is the most suitable distance for impermeable spur dike spacing. The highest magnitude of bed shear stress and turbulent kinetic energy was consistently observed around the second spur dike in the series. Koken and Gogus [16] studied the effect of spur dike length on bed shear stress distribution. The local scour morphology and flow field characteristics of spur dikes with different spacings are investigated by a combination of the flume experiment and numerical simulation. The variations in velocity, turbulent kinetic energy, and shear stress associated with variations in spur dike spacing are discussed
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