[PDE&A] Anna Felden: : From the micro- to the km- scale: applications for every need with the AMR framework Chombo

19 September 2024 16:00 till 17:00 - Location: EEMCS Hall F 36.HB.00.260 | Add to my calendar

This talk will be centered around applications developed with the LBNL’s Adaptive Mesh Refinement (AMR) framework Chombo. Chombo includes features that improve both scalability and accuracy that are not typically found in commercial software packages, e.g., parallel nonlinear implicit solvers and higher-order time integrators and discretizations. The AMR capability is particularly well suited to problems exhibiting a large range of spatial scales, such as the ones that will be discussed in this talk.

In a first part, I will discuss SUHMO, a 2D SUbglacial Hydrology MOdel.
Modeling subglacial hydrology is very challenging because of the large variety of subglacial elements which dynamically evolve over time -from channels to vast subglacial lakes. We handle the strong non-linearities present in the equations by resorting to an efficient non-linear Full Approximation Scheme (FAS-MG) algorithm. We accommodate the transition from unresolved to resolved elements with a novel diffusion-like term which enables to recover second-order convergence of all the variables of interest. After giving a brief overview of the context, I will outline the details of the algorithm and present convergence analysis results demonstrating its effectiveness.

I will then discuss HotChips, which is a Chombo-based solver for heat management in 3D stacked integrated circuit. 3D stacks consist of multiple layers of material with potentially large variations in thermal conductivity. Since Chombo is best suited for the Finite Volume (FV) method, flux reconstruction techniques that can handle material jumps and 2D heat sources are implemented. The efficiency of the solver is further increased by using anisotropic meshing, since material variations in the z-direction are predominant. The entire algorithm relies on the same efficient nonlinear FAS-MG scheme that could be easily extended to deal with temperature-dependent conductivities.
Examples of 3D simulation results of realistic chip layouts using HotChips are presented along with some comparisons with COMSOL Multiphysics.