Ultrasonic velocity profiler for very low velocity field

• The ultrasonic velocity measurement system for very slow flow was implemented.
• Measurement capability was validated down to 2×10−3 mm/s.
• Overall accuracy was lower than the conventional method by one order of magnitude.
• The flow measurement was demonstrated and velocity profile accuracy was confirmed.

An ultrasonic velocity profile measurement system has been realized that can measure velocities in a very slow flow. The system implements a novel phase difference method that overcomes the low velocity limitation in a conventional signal processing algorithm for the Doppler method. The measurement system consists of pulser/receiver, transducer and digitizer only with all signal processing carried out on a personal computer. The measurement limitation at a very low velocity was examined using signals reflected from a wall which are collected by moving transducer at speeds less than 10−2 mm/s. For velocity profiling, real-time profile measurements were performed, which demonstrated successful results for the flow inside a rotating cylinder.