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Dynamic selection of exposure time for turbulent flow measurements

October 1, 2021

The selection of optimum sampling configurations to measure the aspects of turbulent flow of water depends on the variable being measured, the applied measurement technique, the degree of environmental noise, and flow characteristics in and near the sampling location. This work presents a method to dynamically select the exposure time (SET) during the flow-velocity measurement at each sampling location on the basis of the moving block bootstrap (MBB) technique. The MBB enables near real-time estimation of the confidence intervals and, subsequently, the COV for turbulence parameters. The dynamic SET method has been tested in this work using time series of synthetic turbulent flow-velocity signals. This method was implemented using actual flow-velocity signals recorded with acoustic Doppler velocity (ADVs) instruments and acoustic Doppler current profilers (ADCPs). The results obtained from the implementation of the dynamic SET method show that the sampling time to achieve a defined uncertainty threshold is not the same for different turbulence parameters. Consequently, using the dynamic SET method, the exposure time can be optimized to obtain the turbulence parameters with the required uncertainty level. The dynamic SET method can be implemented in the instrument’s data logger to dynamically select the exposure time during flow measurements for a given uncertainty of the required turbulence parameter.

Publication Year 2021
Title Dynamic selection of exposure time for turbulent flow measurements
DOI 10.1061/(ASCE)HY.1943-7900.0001922
Authors José M. Díaz Lozada, Carlos M. García, Graciela Scacchi, Kevin Oberg
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Hydraulic Engineering
Index ID 70229184
Record Source USGS Publications Warehouse
USGS Organization Central Midwest Water Science Center