阶梯形丁坝区明槽紊流横向涡的统计特征

Statistical characteristics of spanwise vortex in open-channel turbulence with step-shaped spur dike

阶梯形丁坝是常见的航道整治建筑物。基于PIV(Particle Image Velocimetry)水槽试验,研究了阶梯形丁坝区明槽紊流横向涡密度、面积、形状参数、旋转强度的沿程及沿槽宽分布规律。结果表明:(1)涡密度沿水深方向的分布在坝顶及槽底附近均出现波动峰值,沿流向距丁坝越远,涡密度波动越小;(2)丁坝附近同一位置的顺向涡总面积大于逆向涡,垂线上涡面积峰值出现在丁坝顶部并随距水槽中轴距离的减小而减小;(3)丁坝附近横向涡多呈椭圆形,丁坝区槽底处的逆向涡和水面处的顺向涡均呈扁平状;(4)丁坝附近同一位置的逆向涡旋转强度远大于顺向涡,丁坝上游至丁坝段,横向涡旋转强度沿程呈骤减趋势,丁坝段至下游,横向涡旋转强度沿程逐渐趋稳。研究结果可为揭示阶梯形丁坝的局部冲刷机制提供参考。

The step-shaped spur dike is a common waterway regulation structure.Based on the PIV(Particle Image Velocimetry) open-channel experiment,the distribution laws of turbulence lateral vortex density,vortex area,vortex shape parameters,vortex rotation intensity along the longitudinal direction and the transverse direction in the stepshaped spur dike area are studied.The results show that the distribution of vortex density along the water depth direction shows fluctuating peaks near the top and the bottom of the spur dike,and the farther away from the spur dike along the flow direction,the smaller the fluctuation of vortex density.The area of the prograde vortex at the same location near the spur dike is generally larger than that of the retrograde vortex.The peak of the vortex area on the vertical distribution appears at the top of the spur dike and decreases with the distance from the central axis of openchannel.The spanwise vortex near the spur dike is mostly elliptical in shape,and the retrograde vortex at the bottom of the open-channel in the spur dike area and the prograde vortex at the water surface are both flat.The rotation intensity of the retrograde vortex at the same location near the spur dike is much larger than that of the prograde vortex.From the upstream of the spur dam to the spur dam area,the spanwise vortex rotation intensity shows a sharp decrease along the path.From the spur dam area to the downstream,the spanwise vortex rotation intensity gradually stabilizes along the path.