Optimization of Acoustic Doppler Velocimeter Sampling Strategies Using Direct Numerical Simulation of Turbulence Flow

Abstract

The experimental characterization of turbulent flows requires flow velocity
measurements with high temporal and spatial resolutions. This information is generally used in studies and projects related to the determination of the mean velocity flow field, the coefficient of mass transfer between the liquid and suspended particles (sediment, bubbles), rates of agglomeration of suspended solids, calculation of rates of mass transfer between the liquid and the walls (erosion), etc. The Acoustic Doppler Velocimeter (ADV) meets these
requirements and it has been widely used as an experimental device for measuring turbulent flows in the last two decades. The operating principle of the ADV is based on the determination, with high temporal resolution, of the three flow velocity components in a small sampling volume, whose geometry can be modified by the user. Part of the internal signal preprocessing performed in this technology involves temporal and spatial averaging of the
measured data to minimize noise. This work aims to analyze the effects of the internal processing and measurement configuration selected by the user on the estimated parameters characterizing the flow turbulence. To achieve this objective, turbulent channel flow fields simulated with direct numerical simulation were sampled using different sampling strategies simulating the ADV performance. The results show the relative significance of the filtering
effects on turbulence parameters such as mean velocity, turbulence fluctuations, Reynolds stresses, and turbulent kinetic energy for different ADV sampling strategies.