Pressure waves traveling through bubbles within liquids inside tubes undergo significant damping. Scientists from the University of Tsukuba have formulated an equation elucidating this effect, showing that factors such as liquid viscosity and compressibility play roles alongside changes in the tube’s cross-sectional area in causing wave attenuation.
Their findings indicate that the speed at which the tube's cross-sectional area changes plays a crucial role in how much pressure waves diminish within these systems.
Pressure waves moving through liquid-filled tubes containing bubbles, referred to as "bubbly flow," exhibit different characteristics compared to those in liquids without bubbles. This distinction demands an accurate comprehension and management of how these pressure waves travel.
The reduction of pressure waves plays a key role in understanding their propagation characteristics, necessitating the precise determination of attenuation elements and processes. Despite knowing that pressure waves within bubbly flows are very responsive to variations in the tube’s cross-sectional size, the fundamental cause behind this damping effect remains unclear.
In their study published in the International Journal of Multiphase Flow Researchers from the University of Tsukuba created an equation that describes how pressure waves move through tube systems containing bubbles when these tubes have different sizes along their lengths.
Their examination verified that alterations in the tube’s cross-sectional area play a role in reducing pressure waves within bubbly flows. When compared quantitatively against other attenuating elements such as liquid phase viscosity and compressibility, it became clear that the pace at which the tube’s cross-sectional area changes is crucial for controlling how much these pressure waves diminish.
This study enhances our basic comprehension of how pressure waves diminish within bubbly flows. Furthermore, since the equation can be applied to tubes with various cross-sectional shapes, it shows potential for use in bubble creation through the utilization of converging-diverging tubes featuring sudden changes in cross-sectional areas.
More information: Kento Watanabe and colleagues investigated the reduction of pressure waves caused by changes in cross-sectional area within bubbly flows. International Journal of Multiphase Flow (2025). DOI: 10.1016/j.ijmultiphaseflow.2025.105138
Furnished by the University of Tsukubo
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