Abstract: An apparatus for estimating a velocity of at least one scatterer in a medium, the apparatus including a curved array of virtual transducers (T1-Tn) for emitting Archimedean spiral waves in a plurality of predetermined directions of propagation defined by a set of insonification angles, and for receiving, from the at least one scatterer, scattered signals generated by scattering of the Archimedean spiral waves emitted from the curved array of virtual transducers, a driving and processing unit (Uc) for estimating the velocity of the at least one scatterer.