Universal scaling law for jets of collapsing bubbles.

Cavitation bubbles collapsing and rebounding in a pressure gradient ∇p form a "microjet" enveloped by a "vapor jet." This Letter presents unprecedented observations of the vapor jets formed in a uniform gravity-induced ∇p, modulated aboard parabolic flights. The data uncover that the normalized jet volume is independent of the liquid density and viscosity and proportional to ζ ≡ |∇p|R(0)/Δp, where R(0) the maximal bubble radius and Δp is the driving pressure. A derivation inspired by "Kelvin-Blake" considerations confirms this law and reveals its negligible dependence of surface tension. We further conjecture that the jet only pierces the bubble boundary if ζ ≳ 4 × 10(-4).