Large-scale laboratory study of breaking wave hydrodynamics over a fixed bar
Large-scale laboratory study of breaking wave hydrodynamics over a fixed bar
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DOI：
10.1002/2016jc012072
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发表时间：
2017-04
影响因子：
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通讯作者：
A. DominicA.vander;J. Zanden;T. O'Donoghue;D. Hurther;I. Cáceres;S. McLelland;J. Ribberink
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文献类型：
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作者：
A. DominicA.vander;J. Zanden;T. O'Donoghue;D. Hurther;I. Cáceres;S. McLelland;J. Ribberink
本文进行了T = 4 s、H = 0.85 m的规则波在固定横隔海滩剖面上的大型波浪水槽试验。使用LDA和ADV在12个位置沿着破碎棒测量速度剖面。在破碎棒的向岸侧产生的强底流达到0.8 m/s的量级。在破碎区和内碎波区之间出现环流模式。时均湍流动能（TKE）是最大的破碎区的酒吧在岸边的侧倾射流穿透水柱。在这个位置，在酒吧的顶部，在破碎过程中在水面产生的TKE到达底部边界层。在破碎区，TKE不减少到零内的一个波周期，导致高水平的“残余”湍流，因此较低的时间变化TKE相比，以前的研究，平面海滩斜坡上的破碎波。有人认为，这种残余湍流的结果从断路器酒吧槽的几何形状，这使得更大的长度尺度和时间尺度的破碎产生的漩涡，并提高了湍流生产内的水柱相比，平面海滩。TKE的传输主要由底流相关的通量，而波浪相关的通量和湍流通量大约小一个数量级。湍流的产生和耗散在破碎带中最大，并且具有相似的量级，但是在浅水区和内碎波区中，产生可以忽略不计，耗散占主导地位。
A large-scale wave flume experiment has been carried out involving a T = 4 s regular wave with H = 0.85 m wave height plunging over a fixed barred beach profile. Velocity profiles were measured at 12 locations along the breaker bar using LDA and ADV. A strong undertow is generated reaching magnitudes of 0.8 m/s on the shoreward side of the breaker bar. A circulation pattern occurs between the breaking area and the inner surf zone. Time-averaged turbulent kinetic energy (TKE) is largest in the breaking area on the shoreward side of the bar where the plunging jet penetrates the water column. At this location, and on the bar crest, TKE generated at the water surface in the breaking process reaches the bottom boundary layer. In the breaking area, TKE does not reduce to zero within a wave cycle which leads to a high level of “residual” turbulence and therefore lower temporal variation in TKE compared to previous studies of breaking waves on plane beach slopes. It is argued that this residual turbulence results from the breaker bar-trough geometry, which enables larger length scales and time scales of breaking-generated vortices and which enhances turbulence production within the water column compared to plane beaches. Transport of TKE is dominated by the undertow-related flux, whereas the wave-related and turbulent fluxes are approximately an order of magnitude smaller. Turbulence production and dissipation are largest in the breaker zone and of similar magnitude, but in the shoaling zone and inner surf zone production is negligible and dissipation dominates.