[论文解读] Acoustic Signatures of Pinch-Off Cavities During Water-Entry

Zirui Liu, Tongtong Ding+5 more|arXiv (Cornell University)|Feb 26, 2026

Fluid Dynamics Simulations and Interactions被引用 0

一句话总结

论文在水进入过程中对厘米级圆柱形弹体带锥鼻的腔体/气泡动力学与辐射声学进行了实验、数值和理论分析，揭示了一个随Froude数尺度化且受边界效应增强的主导腔体振荡频率，在PINCH-OFF后有超过20个声学周期。

ABSTRACT

This study experimentally, numerically, and theoretically investigates the cavity/bubble dynamics and radiated acoustics during the water entry of a centimeter-scale cylindrical projectile with a conical nose. Experiments were conducted in a laboratory tank, employing synchronized high-speed imaging and hydrophone measurements to characterize the cavity closure modes and their resultant acoustic signatures across a range of Froude numbers. The acoustic signal features a weak radiated signal upon impact, followed by significant pressure oscillations spanning more than 20 cycles in the flow field after cavity elongation and pinch-off. A numerical model based on the Finite Volume Method (FVM) successfully captures these physical processes. Subsequently, a semi-theoretical model that incorporates the projectile's boundary effect is developed from potential flow theory. The model not only yields a dominant cavity oscillation frequency that agrees well with experimental data, but also reveals that the boundary effect leads to a cavity oscillation frequency markedly higher than the Minnaert frequency of an equivalent-volume ellipsoidal bubble containing an internal rigid core. The dominant cavity frequency falls nearly linearly with Fr, governed by nose geometry and projectile inertia. This study clarifies the underlying physics connecting cavity dynamics during water entry to underwater acoustic radiation.

研究动机与目标

• Investigate cavity/bubble dynamics during water entry of a centimeter-scale cylindrical projectile with a conical nose.
• Characterize the acoustic signatures emitted during cavity formation, elongation, and pinch-off across a range of Froude numbers.
• Develop experimental, numerical, and theoretical approaches to connect cavity dynamics with underwater acoustics.

提出的方法

• Conduct synchronized high-speed imaging and hydrophone measurements in a laboratory tank to characterize cavity closure modes and acoustics.
• Develop a Finite Volume Method (FVM) numerical model to capture the cavity dynamics and radiated acoustics.
• Create a semi-theoretical model based on potential flow theory that incorporates boundary effects of the projectile.
• Validate the models by comparing dominant cavity frequencies with experimental data.
• Demonstrate how boundary effects modify the cavity oscillation frequency relative to the Minnaert frequency of an equivalent-volume ellipsoidal bubble with a rigid core.

实验结果

研究问题

• RQ1 What cavity closure modes occur during water entry of a centimeter-scale cylindrical projectile with a conical nose?
• RQ2 What acoustic signatures are produced by the cavity dynamics during and after pinch-off?
• RQ3 How does the boundary effect of the projectile influence the dominant cavity oscillation frequency?
• RQ4 How does the dominant cavity frequency scale with Froude number and depend on nose geometry and projectile inertia?

主要发现

• A weak initial acoustic signal is followed by significant pressure oscillations spanning more than 20 cycles after cavity elongation and pinch-off.
• A numerical Finite Volume Method model successfully captures the cavity dynamics and acoustics observed experimentally.
• A semi-theoretical boundary-incorporating model yields a dominant cavity oscillation frequency that agrees with experiments and is higher than the Minnaert frequency for an equivalent-volume ellipsoidal bubble with an internal rigid core.
• The dominant cavity frequency falls nearly linearly with Froude number, governed by nose geometry and projectile inertia.