Development of ultrasonic imaging velocimetry in fluid mechanics

Since the early 1990s, tracer-based optical methods have emerged as the standard non-invasive flow measurement techniques in research laboratories. While very successful they require optical access and a transparent fluid, thus drastically limiting their applicability. Furthermore, the presence of a dispersed phase, even at low concentrations, can render these techniques useless. To overcome this limitation, non-optical techniques like MRI or X-rays were developed. One of the most promising is ultrasound imaging velocimetry (UIV), derived from medical ultrasound imaging. UIV derives from the B-mode imaging typically used in medical ultrasound applications. Once an image has been recorded, PIV-like correlation-based algorithms are used to compute the velocity field. With the revolution of ultrafast imaging in the 2010s, the achievable frame rate is now in the kHz range. Furthermore, ultrafast imaging was extended to 3 dimensions (4D-UIV) using a matrix array of transducers. Unfortunately, the increased number of transducers, with the limited electronics available led to a reduced spatial resolution (32×32). To overcome this issue, a new technique, using a row-column addressed (RCA) array with only 128+128 transducers and based on the coherent compounding of orthogonal plane waves, was proposed. This allows for ultrafast, high- resolution 3D ultrasound imaging. (…)

More informations on the link below.