Lagrangian coherent structures control solute dispersion in heterogeneous poroelastic media

Recent work has demonstrated that Lagrangian chaos can arise at the Darcy scale in even simple poroelastic media, relevant across geophysical, biophysical, and industrial domains. Key factors controlling the onset of chaotic advection in poroelastic media flow include medium heterogeneity, compressibility, and transient forcing. Here we focus on how the range of Lagrangian coherent structures (LCSs) present in poroelastic flows influences the transport of diffusive solutes. We use a minimal two-dimensional sinusoidally forced poroelastic computational model to show that LCS interactions impact the dispersion of solute plumes via the establishment of minimum flux manifolds, leading to strongly anomalous plume moments and solute residence time distributions. We interpret these results with fluid element stretching distributions and local Lyapunov exponents. Anomalous features persist even at low P & eacute;clet number. Our data show that solute dispersion in poroelastic systems subject to transient forcing can only be understood by resolving the LCSs of these complex flows.