Modal and spectral deconstruction of single liquid hydrogen bubble collapse dynamics in shearing micro-clearance

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Abstract
The violent collapse of a vapor bubble within a confined, high-shear environment commonly occurs in hydrodynamic bearing and apical leaf space, which presents a complex interplay of inertial, viscous, and thermal effects. The special thermodynamic properties of cryogenic fluids like liquid hydrogen (LH2) induce highly sensitive cavitation. The collapse dynamics of a single LH2 bubble within a shearing micro-clearance is numerically investigated by the thermodynamic-modified cavitation model. The transient, multi-scale physics are deconstructed using proper orthogonal decomposition, dynamic mode decomposition, and fast Fourier transform. The increase in shearing rate leads to a significant attenuation of the peak pressure impact generated during the violent collapse phase. This pressure reduction is quantitatively linked to the interplay of inertial, viscous, and surface tension forces, as characterized by the Reynolds and Weber numbers. The frequencies and time–frequency features of pressure and mass transfer oscillations are also shown to be strongly modulated by the shearing rate and confinement height. The analysis results reveal that high shearing rates dissipate oscillatory energy more effectively throughout the collapse–rebound period, thereby mitigating the final localized pressure pulse. This study provides a foundation for understanding and potentially controlling cryogenic cavitation dynamics in high-performance fluid systems.

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