Bias in mean velocities and noise in variances and covariances measured using a multistatic acoustic profiler: the Nortek Vectrino Profiler
Bias in mean velocities and noise in variances and covariances measured using a multistatic acoustic profiler: the Nortek Vectrino Profiler
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使用多静态声学轮廓仪测量的平均速度偏差以及方差和协方差中的噪声：Nortek Vectrino Profiler
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
T. Mulder
中科院分区：
文献类型：
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作者：
Robert E. Thomas;L. Schindfessel;Stuart J. McLelland;S. Creëlle;T. Mulder
本文汇编了Nortek Vectrino Profiler的技术特点和工作原理，并回顾了以前报告的用户体验。然后提出了一系列的实验，调查仪器的行为和性能，特别注重在配置文件内的变化。首先，受控测试研究声振幅（和信噪比，SNR）和脉冲间相关系数R2对接种浓度和细胞几何形状的灵敏度。第二，一种新的方法，系统地通过一个单一的绝对垂直位置移动剖析细胞调查平均速度，SNR和噪声的灵敏度：（a）发出的声音强度和存在（或不存在）的声播种;和（B）在理想的声播种条件下变化的流速。一个新的解决方案，推导出量化的噪声影响的两个垂直的三站系统的Vectrino剖面仪和它的贡献的雷诺应力张量的分量。结果表明，对于Vectrino Profiler：1。最佳声学播种浓度为~3000至6000 mg L−1; 2.平均速度幅度在近端细胞中被变量偏置，但在远端细胞中被一致地低估; 3.噪声呈抛物线变化，在收发器下方50 mm处的“最佳点”附近具有最小值; 4.接收器波束仅在最佳点处相交，并且在更靠近和更远离收发器处发散。这种分歧显着减少了远离甜蜜点的采样区域的大小，降低了数据质量; 5.最可靠的速度数据通常收集在收发器下方大约43和61 mm之间的区域中。
This paper compiles the technical characteristics and operating principles of the Nortek Vectrino Profiler and reviews previously reported user experiences. A series of experiments are then presented that investigate instrument behaviour and performance, with a particular focus on variations within the profile. First, controlled tests investigate the sensitivity of acoustic amplitude (and Signal-to-Noise Ratio, SNR) and pulse-to-pulse correlation coefficient, R2, to seeding concentration and cell geometry. Second, a novel methodology that systematically shifts profiling cells through a single absolute vertical position investigates the sensitivity of mean velocities, SNR and noise to: (a) emitted sound intensity and the presence (or absence) of acoustic seeding; and (b) varying flow rates under ideal acoustic seeding conditions. A new solution is derived to quantify the noise affecting the two perpendicular tristatic systems of the Vectrino Profiler and its contribution to components of the Reynolds stress tensor. Results suggest that for the Vectrino Profiler: 1. optimum acoustic seeding concentrations are ~3000 to 6000 mg L−1; 2. mean velocity magnitudes are biased by variable amounts in proximal cells but are consistently underestimated in distal cells; 3. noise varies parabolically with a minimum around the ‘sweet spot’, 50 mm below the transceiver; 4. the receiver beams only intersect at the sweet spot and diverge nearer to and further from the transceiver. This divergence significantly reduces the size of the sampled area away from the sweet spot, reducing data quality; 5. the most reliable velocity data will normally be collected in the region between approximately 43 and 61 mm below the transceiver.