Frequency-dependent properties of multiphase materials: origins,needs, and effective use in geophysics and modern synthetic materials.

Dynamic processes in multiphase materials, e.g., fluid-filled sandstones or bones, are described by models that include frequency-dependent properties. The origin of such properties is introduced as an averaged representation of frequency-dependent microscale motions. In addition to classical frequency-dependence of fluid flow, the influence of weak, high-porosity materials and fluid-fluid interfaces is discussed. The relevant characteristic numbers are contrasted and specific situations are demonstrated, in which frequency dependence has to be considered or not. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)