Measuring the diameter of rising gas bubbles by means of the ultrasound transit time technique

• Ultrasound transit time technique (UTTT) is applied to the zig-zag raise of gas bubble.
• Comparison of bubble diameter and tilt, measured by UTTT, with high-speed imaging.
• Uncertainty in the determination of the bubble diameter by UTTT is less than 7%.
• UTTT is able to measure dynamic changes in bubble size in opaque liquids and vessels.
• UTTT can be applied to liquid metal loops.

This study presents ultrasound transit time technique (UTTT) measurements of the diameter variations of single argon bubbles rising in a zig-zag trajectory in water. Simultaneous size measurements with a high-speed camera show that UTTT resolves both the apparent diameter and the tilt of the bubble axis with an accuracy of better than 7%. This qualifies UTTT for the measurement of bubble sizes in opaque liquids, such as liquid metals, or vessels.