Cross-sectional area variation as a key factor in pressure wave attenuation in bubbly flows: A theoretical analysis

Pressure waves propagating through bubble-containing liquids in tubes experience considerable attenuation. Researchers at the University of Tsukuba have derived an equation describing this phenomenon, demonstrating that beyond liquid viscosity and compressibility, variations in tube cross-sectional area contribute to wave attenuation.

Their analysis reveals that the rate of change in tube cross-sectional area represents a critical parameter governing pressure wave attenuation in such systems.

Pressure waves propagating through bubble-containing liquids in tubes, known as “bubbly flow,” behave distinctly from those in single-phase liquids, necessitating precise understanding and control of their propagation processes.

Pressure wave attenuation is particularly crucial in characterizing these propagation dynamics, requiring clear identification of attenuation factors and mechanisms. Although pressure waves in bubbly flows are known to be highly sensitive to changes in tube cross-sectional area, the underlying attenuation mechanism has remained unresolved.

In their study published in the International Journal of Multiphase Flow, researchers at the University of Tsukuba developed an equation describing pressure wave propagation in bubbly flows through tubes with varying cross-sectional areas.

Their analysis confirmed that changes in tube cross-sectional area contribute to pressure wave attenuation in bubbly flows. Quantitative comparisons with other attenuation factors, including liquid phase viscosity and compressibility, revealed that the rate of change in tube cross-sectional area is a key parameter governing pressure wave attenuation.

This research advances the fundamental understanding of pressure wave attenuation in bubbly flows. In addition, because the equation accommodates tubes of arbitrary cross-sectional shapes, it has promising applications in bubble generation utilizing converging-diverging tubes with abrupt cross-sectional area variations.