Unraveling Anomalous Thermal Transport in Fracture-Matrix Systems: Interplay Between Advective Transport and Matrix Conduction

Slides presented by Alessandro Lenci at the European Geosciences Union General Assembly 2026, session HS8.1.1 “Multiscale characterization of structure, flow and transport processing in fracture-porous media and karst systems”, Vienna, Austria & Online, 3–8 May 2026. The presentation discusses anomalous thermal transport in fracture–matrix systems, focusing on the interplay between advective transport in heterogeneous fracture flow and conductive heat exchange with the surrounding matrix. A physics-based time-domain random walk framework is used to represent channelized advection, matrix-induced memory, and Lévy–Smirnov trapping times. The slides summarize results on mean displacement, displacement variance, breakthrough behavior, and heat exchange efficiency across different thermal Péclet numbers, fracture closures, and correlation structures. The results highlight a transition from early-time channeling-controlled transport to long-time matrix-diffusion-controlled memory. This presentation builds on collaborative work with Yves Méheust, Maria Klepikova, Vittorio Di Federico, and Daniel M. Tartakovsky, and on results published in Lenci et al. (2026, Journal of Fluid Mechanics).