破碎波作用下沙坝附近悬浮泥沙浓度试验研究

Experimental study on suspended sediment concentration near sand bars under action of breaking waves

岸滩中较大部分的侵蚀和淤积都集中发生在波浪破碎带,分析该区域的水动力特性有助于探寻沙坝附近悬浮泥沙变化规律。在波浪水槽中采用中值粒径为0.47 mm的原型沙铺设1∶20坡度的底床进行了相关试验。试验结果显示:斜坡沙坝附近的悬浮泥沙浓度历时曲线呈倒"V"形分布,先增大再减小,最后趋于稳定;破碎带沙坝附近的悬浮泥沙浓度受波浪水深影响较大,并不随着波高的增大呈现规律性的变化;较小的沙坝顶悬浮泥沙浓度通常出现在入射波浪能量以及平均水流相对较小的波浪作用下;波浪相对平静期间,波浪流速的紊动强度较小,悬浮泥沙浓度较小。

The beach erosion and sedimentation mostly concentrate in a wave fracture zone. Therefore, studying the hydraulic characteristics near this zone can explore the change law of suspended sediment concentration near a sand bar. Corresponding ex- periment, using prototype sand with median size 0.47mm, was carried out in a wave flume with 1：20 sloping sandy seabed. The experimental results show that the profile of suspended sediment concentration near the sand bar is like inverted ＂V＂ type, which increases firstly and then decreases, and finally tends to be stable. The suspended sediment concentration in wave fracture zone near the sand bar is influenced by the wave depth, however no regularity relation with the increasing of wave height was found. The relative small suspended sediment concentration above the sand bar usually appears in the wave action characterized by smal- ler incident wave energy and average flow. When the wave is relatively calm, its turbulent intensity of velocity and the suspended sediment concentration are smaller.