DYNAMIC SELECTION OF EXPOSURE TIME FOR TURBULENT FLOW MEASUREMENTS

DÍAZ LOZADA, JOSÉ MANUEL; GARCIA, CARLOS MARCELO; SCACCHI, GRACIELA; OBERG, KEVIN

JOURNAL OF HYDRAULIC ENGINEERING

ASCE-AMER SOC CIVIL ENGINEERS

Lugar: Reston, Virginia; Año: 2021 vol. 147

0733-9429

The selection of optimum sampling configurations for measuring 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 select the exposure time (SET) dynamically during the flow-velocity measurement at each sampling location based on the Moving Block Bootstrap (MBB) technique. The MBB enables the near real-time estimation of the confidence intervals and, subsequently, the coefficient of variation (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 of the implementation of the dynamic SET method show 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 in order todynamically select the exposure time during flow measurements for a given uncertainty of the required turbulence parameter.