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Measurement of the inner structure of turbidity currents by ultrasound velocity profiling
International Journal of Multiphase Flow ( IF 3.8 ) Pub Date : 2021-03-01 , DOI: 10.1016/j.ijmultiphaseflow.2020.103540
Jumpei Hitomi , Shun Nomura , Yuichi Murai , Giovanni De Cesare , Yuji Tasaka , Yasushi Takeda , Hyun Jin Park , Hide Sakaguchi

Abstract The inner velocity structure and particle concentration profile of opaque turbidity currents were measured simultaneously by ultrasound velocity profilers. Currents consisting of a quartz particle suspension were generated by using the lock-exchange method in a flume to experimentally reproduce the quasi-steady state of a turbidity current. A pair of ultrasound transducers captured the horizontal and vertical velocities from Doppler frequencies, and the particle concentration profile was extracted from the echo amplitude. The data obtained were analyzed in terms of momentum conservation according to the two-fluid model. We found that: i) the viscous and Reynolds shear stresses balance in the top half of the current; and ii) the lower border of the stress balancing appears around the depth of the maximum vertical density gradient. These findings indicate that the reduction of flow resistance inside the body region of the turbidity current is maintained downstream, which enables the current to transport particles over a long distance.

中文翻译:

用超声速度剖面测量浊流内部结构

摘要 超声速度剖面仪同时测量了不透明浊流的内部速度结构和粒子浓度剖面。由石英颗粒悬浮液组成的电流是通过在水槽中使用锁交换方法产生的,以实验性地再现浊流的准稳态。一对超声换能器从多普勒频率捕获水平和垂直速度,并从回波幅度中提取粒子浓度分布。根据二流体模型在动量守恒方面对获得的数据进行分析。我们发现:i) 粘性和雷诺剪切应力在电流的上半部分平衡;ii) 应力平衡的下边界出现在最大垂直密度梯度的深度附近。
更新日期:2021-03-01
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