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We study the collapse and expansion of a cavitation bubble in a deformable porous medium. We develop a continuum-scale model that couples compressible fluid flow in the pore network with the elastic response of a solid skeleton. Under the assumption of spherical symmetry, our model can be reduced to an ordinary differential equation that extends the Rayleigh–Plesset equation to bubbles in soft porous media. The extended Rayleigh–Plesset equation reveals that finite-size effects lead to the breakdown of the universal scaling relation between bubble radius and time that holds in the infinite-size limit. Our data indicate that the deformability of the porous medium slows down the collapse and expansion processes, a result with important consequences for wide-ranging phenomena, from drug delivery to spore dispersion.

We present the method of direct van der Waals simulation (DVS) to study computationally flows with liquid-vapor phase transformations. Our approach is based on a discretization of the Navier-Stokes-Korteweg equations, which couple flow dynamics with van der Waals’ nonequilibrium thermodynamic theory of phase transformations, and opens an opportunity for first-principles simulation of a wide range of boiling and cavitating flows. The proposed algorithm enables unprecedented simulations of the Navier-Stokes-Korteweg equations involving cavitating flows at strongly under-critical conditions and 𝒪(10⁵) Reynolds number. The proposed technique provides a pathway for a fundamental understanding of phase-transforming flows with multiple applications in science, engineering, and medicine.

While theoretical estimates suggest that cavitation of water should occur when pressure falls much below −25 MPa at room temperature, in experiments, we commonly observe conversion to vapor at pressures of the order of 3 kPa. The commonly accepted explanation for this discrepancy is that water usually contains nanometer-sized cavitation nuclei. When the pressure decreases, these nuclei expand and become visible to the naked eye. However, the origin of these cavitation nuclei is not well understood. An earlier work in this field has mainly focused on the inception of nuclei which are purely composed of water vapor, whereas experimental data suggest that these nuclei are mainly composed of air. In this Letter, we develop a theoretical approach to study the inception of cavitation nuclei in water with uniformly dissolved air, using a diffuse interface approach. We derive equations which govern the transition of water with uniformly dissolved air to a critical state. Our results show that the dissolved air decreases the free energy barrier from the initial to the critical state, thereby aiding the formation of cavitation nuclei. This study opens up possibilities to explore cavitation inception in fluids containing dissolved gases.