Improvement of Acoustic Doppler Velocimetry in bubbly flow measurements as applied to river characterization for kinetic turbines

• Published in: International journal of multiphase flow Vol. 37; no. 8; pp. 919 - 929
• Main Authors: Birjandi, Amir Hossein, Bibeau, Eric Louis
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2011; Elsevier
• Subjects: Acoustic Doppler Velocimetry (ADV); Acoustics; Air bubbles; Applied sciences; Bubbly flow; Doppler; Doppler effect; Energy; Energy of waters: ocean thermal energy, wave and tidal energy, etc; Exact sciences and technology; Kinetic turbines; Natural energy; Renewable energy; River characterization; Rivers; Spikes; Turbulence; Two-phase flow; Velocimetry; Velocity measurement; Spikes; Turbulence; River characterization; Kinetic turbines; Bubbly flow; Renewable energy; Two-phase flow; Acoustic Doppler Velocimetry (ADV); Air bubbles; Two phase flow; Speed measurement; Turbine; Rivers; Experimental study; Acoustic Doppler velocimeter; Test facility; Energy of waters; Bubble flow; Electric power production; Kinetic energy
• ISSN: 0301-9322; 1879-3533
• DOI: 10.1016/j.ijmultiphaseflow.2011.05.001

► Filter enables ADV to measure liquid flow velocities in bubbly flows. ► Filter performance remains unaffected by bubble density. ► River velocity measurements show that filtering is an essential step to obtain flow and turbulence characteristics. Acoustic Doppler Velocimetry (ADV) can measure flow velocities in three directions in experimental facilities and field applications. Based on the Doppler shift effect, ADV can accurately resolve the quasi-instantaneous flow field at frequencies of up to approximately 200 Hz. However, this technique is sensitive to operating conditions that can lead to contaminated signals containing large amplitude spikes, a disadvantage of ADV. Aliasing of the Doppler signal creates these spikes. Such a situation occurs when large particles intersect the sampling volume or acoustic waves. For example during the characterization of river velocities, sediments floating near the riverbed cause aliasing from particles, and more importantly, surface entrained air bubbles contaminate the ADV signal. Spikes due to air bubbles not only increase the standard deviation of the velocity, but also corrupt the autocorrelation and power spectra. As some of these spikes appear like velocity fluctuations, developing accurate despiking procedures is an important requirement during post-processing of ADV velocity measurements in bubbly flow applications. A new hybrid method is introduced which has advantages over conventional despiking methods such as the acceleration thresholding method and the phase-space thresholding method when using ADV in bubbly flow. ADV river velocity measurements near kinetic turbines demonstrate the proposed method. This method is applicable to other bubbly flow applications to characterize the liquid phase using ADV.