Computations of 3D turbulent flow structures around submerged spur dikes under various hydraulic conditions

摘要

This paper describes the numerical study on 3D turbulent flow structures around submerged spur dikes. Effects of three hydraulic parameters, S/L (S: interval length of two spur dikes, L: length of spur dikes), T/h (T: height of spur dikes, h: depth), θ (= inclination angle), are examined through the comparison of numerical results and previous experimental results focusing on both time-mean and time-dependent aspects. A non-liner k-ε model is adopted as a turbulence model to reproduce the vortex shedding from a tip of a spur dike and secondary currents. The numerical results show that the flow near the bed, which is particularly important for sediment transport, is affected by both inclination angle and the ratio of T/h. In the downstream inclined spur dikes, the unsteady vortex shedding is generated from the first spur dike and the period is determined by the feedback effect of impinging shear layer. The frequency jump of the vortex shedding can be seen between S/L = 2 and S/L = 4 in the numerical results.