Wave-induced shallow-water monopolar vortex: large-scale experiments
Wave-induced shallow-water monopolar vortex: large-scale experiments
复制标题
DOI：
10.1017/jfm.2020.980
复制
发表时间：
2021-01-11
影响因子：
3.7
通讯作者：
Lynett, P. J.
中科院分区：
文献类型：
--
作者：
Kalligeris, N.;Kim, Y.;Lynett, P. J.
据报道，在最近的海啸事件中，对海啸引起的港口涡流进行了大量的实地观测。本文通过一系列大尺度实验，研究了长波作用下浅水单极涡旋的演化过程。在直立式防波堤背风面，不对称波通过窄槽形成水流分离区，并与瞬变流耦合形成单极湍流拟序结构。从尾喷流分离后的涡流在实验持续时间的剩余时间内是完全湍流的（Re-h类似于O（10（4）-10（5）。自由表面的速度场提取通过粒子跟踪测速在几个实验测试。Seol和Jirka（J. FluidMech.，第665卷，2010年，pp. 274-299）对浅水涡的衰减和空间增长的预测与实验数据吻合较好。预测底部摩擦引起t（-1）方位角速度衰减，湍流粘性扩散导致体积涡径向增长，其中t代表时间。通过一个理想的地球物理涡，方位角速度，涡度和自由表面的高度轮廓很好地描述。运动学自由表面边界条件预测在TCS中心弱上升流，其次是一个区域的下降流在回流模式沿着水柱。通过二次和一次表面速度场中所含动能的比率来量化流动的垂直限制，并确定了朝向准二维流动的过渡点。
Numerous field observations of tsunami-induced eddies in ports and harbours have been reported for recent tsunami events. We examine the evolution of a turbulent shallow-water monopolar vortex generated by a long wave through a series of large-scale experiments in a rectangular wave basin. A leading-elevation asymmetric wave is guided through a narrow channel to form a flow separation region on the lee side of a straight vertical breakwater, which coupled with the transient flow leads to the formation of a monopolar turbulent coherent structure (TCS). The vortex flow after detachment from the trailing jet is fully turbulent (Re-h similar to O(10(4)-10(5))) for the remainder of the experimental duration. The free surface velocity field was extracted through particle tracking velocimetry over several experimental trials. The first-order model proposed by Seol& Jirka (J. FluidMech., vol. 665, 2010, pp. 274-299) to predict the decay and spatial growth of shallow-water vortices fits the experimental data well. Bottom friction is predicted to induce a t(-1) azimuthal velocity decay and turbulent viscous diffusion results in a v t bulk vortex radial growth, where t represents time. The azimuthal velocity, vorticity and free surface elevation profiles are well described through an idealised geophysical vortex. Kinematic free surface boundary conditions predict weak upwelling in the TCS-centre, followed by a zone of downwelling in a recirculation pattern along the water column. The vertical confinement of the flow is quantified through the ratio of kinetic energy contained in the secondary and primary surface velocity fields and a transition point towards a quasi-two-dimensional flow is identified.