Vortex imaging using two-dimensional ultrasonic speckle correlation

In previous work, it has been shown that ultrasonic speckle velocimetry can be used to measure local particle velocities in flows. So far the technique has been applied to monitor stationary processes. In this paper, we show how ultrasonic speckle velocimetry can be used to dynamically map the two-dimensional velocity profiles of vortices caused by an obstacle within a flow. Thanks to the great versatility of our multi-channel system, it is possible to capture as much as 5000 images per second, thus enabling us to monitor very fast moving processes. To date, two transducer arrays are used to estimate the 2D motion vector of local particles. We also discuss possible modifications and improvements of the system that could lead to the use of a single array of transducers to dynamically map the vectorial velocity fields of flows