Theoretical and experimental study of resonance of blobs in porous media

We theoretically and experimentally investigated the frequency response of blobs in porous media to an oscillatory pressure difference. (The term blob refers to a connected liquid mass that occupies one or more pores.) To predict the frequency response analytically, we formulated a simple model pore system consisting of a blob in a capillary tube. This model accounts for the frequency-dependent viscous pressure drops in the blob and the surrounding liquid and for the dynamic capillary pressure that occurs due to contact line pinning. By using the planar laser-induced fluorescence technique, we visualized the dynamic response of blobs in porous media. As predicted by our theory, air and liquid blobs surrounded by an immiscible liquid exhibited resonance in a capillary tube. Furthermore, we showed, for the first time, that a liquid blob in a sphere-packing medium exhibits resonance.