Large Eddy Simulation of Unidirectional and Wave Flows through Vegetation
Large Eddy Simulation of Unidirectional and Wave Flows through Vegetation
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DOI：
10.1061/(asce)em.1943-7889.0001087
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发表时间：
2016-08-01
影响因子：
3.3
通讯作者：
Liu, Don
中科院分区：
文献类型：
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作者：
Chakrabarti, Agnimitro;Chen, Qin;Liu, Don
采用大规模并行大涡模拟(LES)试验，研究了单向流在沉水植被上和波浪通过浮生植被上形成的流场。对于沉水植被，平均和湍流水平和垂直速度的垂直分布与实验室实验结果吻合得很好。根据圆柱体上的深度积分力计算的冠层平均体积阻力系数与经验测量结果吻合得很好。对于新生植被，计算了波浪诱导的阻力，并将惯性系数和压阻系数与实验室实验进行了比较，两者吻合较好。在不同的波浪条件和Keulegan-Carpenter(KC)数下，给出了杆基周围力和力矩的垂直变化，并与单杆情况进行了比较。可以看出，在低Kc数时，惯性力的影响是显着的。结果表明，波谷与波峰之间的自由面流量在一段时间内对圆柱体中心2~3个直径范围内自由面附近速度场的垂直变化有很大影响，在波浪波传播方向上，波谷与波峰之间的自由面通量在圆柱体后形成一个主要的回流区。
Massively parallel large eddy simulation (LES) experiments were conducted to study the flow fields developed by unidirectional flow over submerged vegetation and wave flow-through emergent vegetation. For the submerged vegetation, vertical profiles of mean and turbulent horizontal and vertical velocities were found to be in good agreement with laboratory experiments. Canopy-averaged bulk drag coefficient calculated from the depth-integrated forces on the cylinders compares well with empirical measurements. For the emergent vegetation, wave-induced drag forces were calculated, and the inertia and pressure-drag coefficients were compared with laboratory experiments, which were found to be in good agreement. Vertical variation of forces and moments about the stem base are presented and compared with a single stem case under a variety of wave conditions and Keulegan-Carpenter (KC) numbers. It is seen that at low KC numbers the effect of the inertia force is significant. The vertical variation of the velocity field near the free surface, within two to three diameters from the cylinder center, was found to be considerably influenced by the free surface flux between the wave trough and the crest, over a time period, which creates a predominant recirculation zone behind the cylinder in the direction of wave propagation.