高频声学仪器底床高度野外测量及室内验证

    Field Measurement and Indoor Validation of Bottom Bed Elevation by Using High Frequency Acoustic Instrument

    • 摘要: 河口海岸地区底床的冲淤变化是沉积动力学研究主要内容之一,而野外观测是准确获得现场底床冲淤变化信息的关键。本文利用观测近底边界层三维水动力信息的声学三维多普勒流速仪(Acoustic Doppler Velocimetry,ADV)对长江口南槽底床高度变化进行了野外测量,为验证野外现场实测数据的可靠性,设计了2个室内试验,并对ADV测量底床高度的可行性进行了验证:试验一对比了人工测量的ADV换能器实际距离底床高度H与ADV自身记录的其换能器距离底床高度h,确定了ADV测量底床高度的范围;试验二利用ADV测量静置的高浊度水体,确定了含沙量对ADV测量造成影响。试验结果表明:①由ADV内部存储的vhd数据文件可以直接获取换能器距离底床的高度,但是这一测量结果存在适用范围,换能器实际距离底床高度H需要满足150 mm≤H≤370 mm;②当换能器实际距离底床高度H <150 mm时,可通过提取pck数据文件获取换能器距离底床的高度;③当换能器实际距离底床高度H>370 mm时,仪器无法获取该数值;④当水体含沙量超过14.36 kg/m3时,ADV测量同样无法获取到换能器距离底床高度信息。

       

      Abstract: Change of erosion and deposition of bottom bed in the estuarine and coastal areas is one of the main research contents of sedimentation dynamics, and field observation is the key to obtain accurately the information about changes of scour and silting of the bottom bed. For the in-situ measurement of bed elevation variations in the southern channel of the Yangtze River mouth, an Acoustic Doppler Velocimetry (ADV) instrument, which is used to observe 3D hydrodynamic information of near-bottom boundary layer, is applied. In order to verify the reliability of the measured data in the field, two indoor experiments are designed for verifying the feasibility of the bed elevation measured by using ADV: Experiment 1 is to determine the range of the bottom-bed elevation measured with ADV by comparing the distance from ADV transmitting transducer to bottom bed measured artificially H with that recorded by ADV itself h; and Experiment 2 is to determine the influence of sediment concentration on ADV measurements through measuring the static high turbidity water with ADV. The experimental results show that: ① The distance from the ADV transducer to the bottom bed can be directly acquired through the vhd data file stored inside ADV. However, the results thus measured require the actual height H between the transducer and the bed satisfying 150 mm≤H≤370 mm; ② When the actual height H between the transducer and the bed is less than 150 mm, the actual height H can be obtained by extracting the pck data file; ③ When the actual height H is greater than 370 mm, the instrument cannot obtain the value; and ④ When the sediment concentration exceeds 14.36 kg/m3, there is also no way to obtain the information about actual height H in the ADV measurement.

       

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