title: Capillarity-induced resonance of blobs in porous media: analytical solutions, Lattice-Boltzmann modeling, and blob mobilization.
abstract: Theoretical considerations and experiments in capillary tubes suggest that blobs exhibit resonance in porous media when they are trapped because of interfacial tension. Here, we investigate the hypothesis that such blobs can be mobilized by exploiting a phenomenon entitled capillarity-induced resonance, that is, by exciting the blobs at their resonant frequency. We used Lattice-Boltzmann (LB) modeling to perform numerical experiments, and we validated the LB model using analytical solutions that approximate the linear response of blobs with pinned menisci in straight and polygonal pore channels to an oscillatory body force. The LB simulations agree well with the quasistatic response, which the analytical solutions describe correctly. Furthermore, the frequency response, particularly the resonant frequency, agrees well, even though the analytical solutions do not accurately estimate viscous pressure drops. Numerical experiments in polygonal and sinusoidal pore channels, as well as disc packings, show that blobs, which are trapped even though a constant body force is applied, can indeed be mobilized by exploiting capillarity-induced resonance. Moreover, the resonant frequency can be estimated in numerical experiments by determining the dominant frequency in the blob amplitude in response to a force pulse. This is of great practical relevance for complex geometries, for which the resonant frequency cannot be easily predicted theoretically.
authors.affiliation: Johns Hopkins University, Department of Geography and Environmental Engineering, 313 Ames Hall, 3400 N. Charles St., Baltimore, MD, USA. markus_hilpert@jhu.edu
authors.forename: Markus
authors.initials: M
authors.lastname: Hilpert