It can be observed that a good qualitative profile (shown with diamonds) was obtained at the lowest voltage setting using DMEA data and the Time Domain (TD) velocity estimator. Velocity profiles estimated using the built in algorithm of the UVP monitor seemed to correlate better with the TD algorithm as the voltage was increased (see Commercial algorithm 150 V result). Similar results were found using the standard transducer, except that the profiles measured at 90 V already showed good agreement with the custom algorithm, due to the higher energy output of the standard transducer in the CMC fluid (see Section 4.1). Also, when the time domain algorithm was replaced with the frequency domain algorithm, similar profiles were obtained for both transducers at different voltage settings. However, some discrepancies were found between the time and frequency domain algorithms when compared separately (discussed in Section 4.4.2).
Fig. 16 shows profiles measured using the delay line transducer in bentonite 8% w/w (K = 0.0128, n = 1, τy = 18.7) at a flow rate of 0.5 l/s (Re2 = 156). The UVP system parameters were kept constant while the number of ultrasonic pulse repetitions (32–512) per profile was varied.