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1 2022

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Effects of sampling configurations of acoustic Doppler velocimeter (ADV) on turbulence measurements around large roughness elements

Golpira Amir, Baki Abul B. M., Azimi Amir H.

Acta Geophysica

2022

Vol. 70, no 5

2251--2267

In this experimental study, the effects of sampling strategies on the acoustic Doppler velocimeter (ADV) measurements in clear water flow around a boulder, including the near-bed and boulder’s wake regions, were investigated. This study found that adjusting sampling volume heights and frequencies noticeably influenced the mean and turbulent flow characteristics, especially measurements of time-averaged velocity and the Reynolds shear stress near the bed. Increasing sampling frequency and reducing sampling volume size improve ADV quality parameters while it increased the noise variances. Generally, the recorded mean and turbulent flow parameters with the smallest sampling volume and the highest frequency showed the least sensitivity to applying a signal correlation filter. Assuming the normality of true velocity data, this study found that by keeping at least 70% of data, average signal correlation thresholds as low as 57% and 40% can be applied for filtering of measurements in the near-bed and boulder’s wake regions, respectively. These findings indicated that applying common strict signal correlation thresholds is not necessarily the best practice to filter velocity data in the near-bed and turbulent regions.