Acoustic measurement of suspended sediment concentration profiles in an oscillatory boundary layer

The use of an Ultrasonic Velocity Profiler (UVP) to obtain phase-averaged velocity and turbulent Reynolds stress profiles inside an oscillatory boundary layer flow is described in detail and possible error sources are summarized. Since the instrument also reports the acoustic backscatter, a novel application of the same ultrasound profilers to obtain phase-averaged suspended sediment concentration profiles and the errors involved in this technique are carefully discussed. The experiments were performed in the Large Oscillatory Water-Sediment Tunnel (LOWST), which has been a recent addition to the experimental facilities of the Ven Te Chow Hydrosystems Laboratory at the University of Illinois at Urbana-Champaign. The results showed that for the selected transducer frequency and flow, the instrument ability to characterize turbulence is compromised by the presence of Doppler noise and the size of the sampling volume. Regarding the suspended sediment estimation, it was found that the calibration obtained using water samples yielded good results, allowing for the study of the suspended sediment evolution along the oscillation.