Shock waves from non-spherical cavitation bubbles
| Autor: | Supponen, Outi, Obreschkow, Danail, Kobel, Philippe, Tinguely, Marc, Dorsaz, Nicolas, Farhat, Mohamed |
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| Rok vydání: | 2017 |
| Předmět: | |
| Zdroj: | Phys. Rev. Fluids 2, 093601 (2017) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevFluids.2.093601 |
| Popis: | We present detailed observations of the shock waves emitted at the collapse of single cavitation bubbles using simultaneous time-resolved shadowgraphy and hydrophone pressure measurements. The geometry of the bubbles is systematically varied from spherical to very non-spherical by decreasing their distance to a free or rigid surface or by modulating the gravity-induced pressure gradient aboard parabolic flights. The non-spherical collapse produces multiple shocks that are clearly associated with different processes, such as the jet impact and the individual collapses of the distinct bubble segments. For bubbles collapsing near a free surface, the energy and timing of each shock are measured separately as a function of the anisotropy parameter $\zeta$, which represents the dimensionless equivalent of the Kelvin impulse. For a given source of bubble deformation (free surface, rigid surface or gravity), the normalized shock energy depends only on $\zeta$, irrespective of the bubble radius $R_{0}$ and driving pressure $\Delta p$. Based on this finding, we develop a predictive framework for the peak pressure and energy of shock waves from non-spherical bubble collapses. Combining statistical analysis of the experimental data with theoretical derivations, we find that the shock peak pressures can be estimated as jet impact-induced hammer pressures, expressed as $p_{h} = 0.45\left(\rho c^{2}\Delta p\right)^{1/2} \zeta^{-1}$ at $\zeta > 10^{-3}$. The same approach is found to explain the shock energy quenching as a function of $\zeta^{-2/3}$. Comment: Accepted for publication in Physical Review Fluids |
| Databáze: | arXiv |
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