T型丁坝坝翼与坝身夹角及坝轴线中心角对90°弯道水流的影响
Influence of the angle of spur dike wing and spur dike and the central angle of spur dike axis of T-shaped spur dike in a 90° bend

结合下挑丁坝和弯道边界条件的特点，利用三维数值模型研究90°弯道中设置T型丁坝后，丁坝坝翼与坝身的夹角θ以及坝轴线中心角α对回流区大小、丁坝附近横截面主流区流速、横向环流以及最大河床切应力的影响. 研究结果表明，回流宽度随θ的减小而逐渐递增，回流长度在θ=75°时，相对最短，并且回流长度随α的减小而减小. 丁坝附近横截面主流区流速随着θ的减小而减小、当θ减小到45°时会增大，丁坝上下游各截面的流速随α减小略微减小. 河床切应力最大值与平均切应力之比τmax/τ0随Fr的增大呈递减趋势，随θ的减小呈现先递减再反向增加的趋势，当θ=75°时，τmax/τ0的相对值最小；α越小，τmax/τ0越小. 综合研究表明，T型丁坝坝翼与坝身夹角θ为75°且坝轴线中心角α为30°时，可以更好地发挥T型丁坝的体型优势.
This paper researches on the effects of hydraulic characteristics caused by the parameters θ and α meant respectively the angle between spur dike wing and spur dike and central angle of spur dike axis in the 90°bend by using 3D numerical simulation. The results indicate that the width of backflow increases with the decrease in θ and the width of backflow is relatively shortest at θ=75°，while the main-flow velocity decreases with the decrease in θ and it will raise when θ dropped to 45°along with it will decline slightly around spur dike .Besides the length of backflow decreases with the decrease in α. The ratio of the maximum and the average bed-shear stress increases with the increase in Froude number and decreases with the decrease in α，also it provides a trend that the shear stress will decline firstly and then increase with the decrease in θ as well as the ratio is relatively minimum at θ=75°.It is evident that the T-shaped spur dike will be applied in its type advantage at θ=75°and α=30°