ORALS

Natural phenomena have mostly multiphysics and multiscale character. The same is true for many manmade materials. Multiphysics and multiscale models, if based on sound physical principles and satisfying the numerical requirements such a consistency and stability, can give much more insight in the phenomena under investigation than simpler models and can even allow for discoveries. I shall address a few of these cases where complex models made the difference. The use of an appropriate u-p model allowed to find that cavitation is needed for the onset of localization in dilatant porous media [1]. It also allowed to identify internal length scales governing the phenomenon. A three-fluids model for concrete, which considers a chemo-thermo-hydro-mechanical analysis taking into account of dry air, capillary and adsorbed water and water vapour in the pores allowed for a unified treatment of concrete under very high temperatures with particular regard to thermal spalling, tunnel fires and reactor vessels, concrete at early ages and beyond, leaching, Alkali-Aggregate reactions, freezing and thawing [2,3]. A model for fracturing in saturated porous media based on Biot’s theory, standard Galerkin Finite Elements, cohesive fracture and remeshing enabled to discover at least for the mechanics community that fracturing in saturated porous media is not continuous but stepwise with ensuing pressure oscillations [4,5]. This has important implications both in hydraulic fracturing operations and in geophysics, among others to reproduce the en echelon structure observed in nature. In material mechanics a truly multiscale model allowed to predict correctly the residual strains after cool down of Nb3 Sn superconducting strands [6]. Finally a multiphase model based on an transport oncophysics framework enabled to identify for instance a way to obtain less dense tumors which are desirable for drug delivery [7]. Other examples will be shown in the presentation.

References:
1. “A multiphase media model for simulation of localisation and post localisation behaviour in geomaterials” (with L. Sanavia and C.E. Majorana), Mechanics of Cohesive -Frictional Materials and Structures, 1, 1 (1996), 95-114.
2. “Thermo-hygro-mechanical analysis of concrete” (with P. Baggio and C.E. Majorana), Num. Meth. in Fluids, 20 (1995), 573-595.
3. “Modeling evolution of frost damage in fully saturated porous materials” (with M. Koniorczyk and D. Gawin), Comput. Methods Appl. Mech. Engrg., 292 (2015), 38-61.
4. “Mesh adaptation and transfer schemes for discrete fracture propagation in porous materials” (with S. Secchi and L. Simoni), Int. J. Numer. Anal. Meth. Geomech., (2007), 31:331-345