Department of Mathematics

Indian Institute of Science

Bangalore 560 012

 

SEMINAR

 

Speaker

:

Hari Shankar Mahato
Affiliation : University of Georgia, USA

Subject Area

:

Mathematics

 

Venue

:

Department of Mathematics, Lecture Hall I

 

Time

:

11:00 a.m.

 

Date  

:

January 10, 2015 (Tuesday)

Title

:

"Upscaling of a System of Semilinear Diffusion‐Reaction
Equations in a Heterogeneous Medium: Multi‐Scale Modeling and
Periodic Homogenization."
Abstract

:

A porous medium (concrete, soil, rocks, water reservoir, e.g.) is a multi‐scale medium where the heterogeneities present in the medium are characterized by the micro scale and the global behaviors of the medium are observed at the macro scale. The upscaling from the micro scale to the macro scale can be done via averaging methods. In this talk, diffusion and reaction of several mobile chemical species are considered in the pore space of a heterogeneous porous medium. The reactions amongst the species are modelled via mass action kinetics and the modelling leads to a system of multi‐species diffusion‐ reaction equations (coupled semi‐linear partial differential equations) at the micro scale where the highly nonlinear reaction rate terms are present at the right hand sides of the system of PDEs, cf. [2]. The existence of a unique positive global weak solution is shown with the help of a Lyapunov functional, Schaefer’s fixed point theorem and maximal Lp‐regularity, cf. [2, 3]. Finally, with the help of periodic homogenization and two‐scale convergence we upscale the model from the micro scale to the macro scale, e.g. [1, 3]. Some numerical simulations will also be shown in this talk, however for the purpose of illustration, we restrict ourselves to some relatively simple dimensional situations. As an extension to the previous model, we consider the mixture of two fluids. For such models, a system of Stokes ;Cahn ;Hilliard equations will be considered at the micro scale in a perforated porous medium. We first explain the periodic setting of the model and the existence results. At the end homogenization of the model will be shown using some extension theorems on Sobolev spaces, two‐scale convergence and periodic unfolding.