This chapter describes complementary studies, which include the design of a small-scale rotational test cell with an annular flow channel, testing it for various applications and characterization of the flow regimes, and the acoustic streaming visualization and quantification in terms of velocity profiles in liquids. Flow speed measurements in the complementary studies were performed using three methods: the ultrasonic transit-time difference, the cross-correlation of the backscattered from particles ultrasonic echoes, the particle image velocimetry.