Ultrasonic Doppler device for measurement of time-dependent and space-dependent flow speed

An effort is made to determine, at each instant, the direction and the magnitude of the velocity of a flow-carried target, provided this target moves within the field monitored by the measuring device. Four transducers (one transmitter and three receivers) are used because the Doppler phenomenon is three-dimensional in the present case. The interaction between the incident ultrasonic wave and the scattering target is modeled by means of a complex envelope. Targets in the form of bubbles injected in the flow are tracked experimentally for a duration of 1 s as they move along a three-dimensional trajectory. This trajectory is reconstructed from velocity results. The proposed 3-D ultrasonic Doppler velocimeter measures the velocity vector and allows reconstruction of the trajectory for targets of 10-μm minimum size, included in a measurement field of some cubic centimeters, with maximum velocity of some meters per second