Estimation of Particle Flow Velocity in a Liquid From Pulse Echo Signals of an Ultrasonic Focusing Transducer

The formation of ultrasonic pulse–echo signals scattered by a flow of small particles in the focal region of a focusing immersion transducer is considered. Numerical simulations show that ultrasonic responses of single scatterers are sensitive to the direction of the motion and position of the trajectory relative to the focus. An experimental study was carried out on a suspension of yeast cells in the frequency range of 50–100 MHz. The measured spatio-temporal signals differ from the simulated responses due to averaging over an ensemble of particles participating in the formation of the signal. The velocity obtained by the ultrasonic method is in good agreement with the data measured by the flow meter in the range of 1–8 mm/s.