High frame rate flow measurement using Ultrasound Imaging Velocimetry

Using ultrasound in plane wave imaging mode, in combination with a proper processing strategy and the covariance function approach, we can not only better estimate the actual turbulence statistics, but we are also able to measure turbulent flows with much higher Reynolds numbers. Optimising the processing strategy by using a sliding correlation average of a few frames is significantly improving the signal-to-noise ratio, with an acceptable decrease in temporal resolution. With the covariance function approach we are able to distinguish noise and signal from each other. This improves the estimation of the actual turbulence statistics. In this study, turbulent pipe flow data for two different Reynolds numbers (5300 and 44000) is compared with literature. For both cases a good agreement is found for the mean velocity profile. Especially in the near-wall region, the estimation for u-rms is improved significantly. For the radial velocity fluctuations, a systematic underestimation is found, which is most likely due to the small displacements in this direction.