An acoustic technique for Lagrangian velocity measurements
Résumé
Ultrasonic transducers array can be used to track solid particles advected by a turbulent flow. The simultaneous use of four linear antennas of transducers gives the 3D position of the particles. The extraction of the Doppler frequency shift gives a precise estimation of velocity components. We describe the principle of the technique, the signal conditioning and the acquisition schemes. We show briefly the performances of the technique applied to a turbulent flow at high Reynolds number. The dynamical range of the measurement is over 55 dB and the frequency response spans over 2 decades. These performances allow us to investigate the inertial time scales of Lagrangian turbulence.
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