Two medical ultrasound scanners were used to acquire the ultrasound images. The transducers used were a linear,  a phased and a flexible linear array. All were operated in plane wave mode at multiple frequencies within their bandwidth. All transducers were stationary submerged in the mud. IN the mud a circular flow was induced using a magnetic stirrer. The flow velocities were unknown. The ultrasound images were processed using the open source OpenPIV script in python. Further processing to of the output of the PIV algorithm, such as analysis of accuracy, standard deviation, ... in function of depth  was done with self written fit-for-purpose python scripts.