Concurrent and Hierarchical Multiscale Modeling for Fluid-infiltrating Solids 


URL: www.ce.ust.hk/Web/EventDetail.aspx?EventId=401



Dr. Steve WaiChing Sun
Assistant Professor 
Department of Civil Engineering & Engineering Mechanics
Columbia University in the City of New York, USA

Date:6th January 2015, Tuesday
Time:11:00 a.m.
Venue: Room 3574 (lift 27 & 28, Conference Room) Academic Building The Hong Kong University of Science and Technology 

Abstract 
The mechanical behavior of a fluid-infiltrating porous solid is significantly influenced by the presence and diffusion of the pore fluid in the void. This hydro-mechanical coupling effect can be observed in a wide range of materials, including rocks, soils, concretes, bones and soft tissues. Nevertheless, due to the high computational demand, explicitly simulating the pore scale solid-fluid interactions remains impractical for engineering problems commonly encountered in the field and basin scales. The objective of this talk is to present two classes of multiscale computer simulation technologies that allow the coupling of micro- and macro-scopic simulations across different spatial and temporal scales. The first class of model is a concurrent coupling model in which the deformation-diffusion problems are casted as the saddle point that optimizes the constrained partitioned incremental work of a multi-field energy functional. By introducing appropriate technology to enforce compatibility across length scales, pore-scale simulations in confined domain can be coupled with large-scale field problems while maintaining numerical stability and accuracy. The second class of multiscale model is a nonlocal hierarchical multiscale framework that couples grain-scale discrete element simulations with a macroscopic explicit dynamics finite element model. This hierarchical nonlocal DEM-FEM coupling retains the simplicity and efficiency of the continuum-based finite element model, while possessing the original length scale of the granular system. The pros and cons of these two different coupling strategies will be demonstrated in numerical examples.

 Biography Dr. Steve Sun is an Assistant Professor in the Department of Civil Engineering at Columbia University. His research focuses on the development of solution techniques for coupled geomechanics problem, and applications of mathematical tools, such as graph theory, Lie algebra, and combined deterministic-stochastic method, for modern engineering problems.

 For enquiries, please contact Miss Cheryl Tang 2358 8848

The poromechanics group has been selected to receive the Provost's Small Grants Program for Junior Faculty who Contribute to the Diversity Goals of the  University from Columbia University. This program is designed to support Schools’ diversity plans, and to assist the University in meeting placement goals established in its affirmative action programs, by advancing the career success of outstanding junior faculty, in disciplines where the availability of qualified minorities and women exceeds their representation on our faculty. 

The poromechanics group is awarded new research grant from Army Research Office to study how moisture content affects the dynamics responses of granular matters in the pendular regime. Professor Sun will serve as the PI and PhD student Kun Wang will serve as GRA for the STIR proposal, which will begin in 1/1/2015. 

Dear colleagues, 

I would like to draw your attention to the upcoming mini-symposia for USNCCM San Diego. The due date is 2/15/2015. Further information can be found in the URL listed below: 

http://13.usnccm.org/

Best Regards,

Waiching Sun


MS308: Multiscale Modeling of Granular Materials

Ahmed Elbanna, University of Illinois Urbana Champaign
Waiching Sun, Columbia university

Granular systems are ubiquitous in our everyday experience. They play a central role in the physics of many natural phenomena that are societally relevant such as slope failures (e.g. landslides and man-made embankment) and earthquakes. Grain transportation, pouring, packing and flowing are also essential processes in many industrial fields such as food, pharmaceutical, and construction material industries.

From a fundamental point of view, granular materials deform in complex, and possibly chaotic, ways. Small scale instabilities on the grain scale, such as cooperative alignment of particles in a given direction, may lead to large scale fragilities on the macroscopic scale such as shear banding and failure. Moreover, granular particles are not necessarily smooth and various types of contact and surface forces exist between them. A multiscale description for deformation is thus essential to take into account the small scale nonlinearities and their implications on the overall behavior; a naive separation between micro and macro scales may be misleading.

This session solicits contributions in the broad area of multiscale modeling of granular materials. Relevant topics include, but not limited to, : (1) constitutive models for granular materials in the dense and hydrodynamic regimes, (2) application of graph theory to granular physics, (3) coupled granular-continuum simulations, (4) modeling strain localization and shear bands in the presence and absence of fluids, and (5) modeling large scale stick slip instabilities as observed in landslides and earthquakes. Experimental studies on microstructures of granular materials via tomographic imaging or digital image correlation techniques are also welcomed.   

MS1005: Multiphysical Modeling of Geomaterials

WaiChing Sun, Columbia University
Qiushi Chen, Clemson University
Craig Foster, University of Illinois at Chicago
Marcelo Javier Sanchez Castilla, Texas A&M University
 
Geomaterials, such as soil, rock and concrete, are multiphase porous materials whose macroscopic mechanical behaviors are governed by grain size distribution and mineralogy, fluid-saturation, pore space, temperature, loading paths and rate, drainage conditions, chemical reactions, and other factors. As a result, predicting the mechanical responses of geomaterials often requires knowledge on how several processes, which often take place in different spatial and temporal domains, interact with each other across length scales.

This mini-symposium is intended to provide a forum for researchers to present contributions on recent advances in computational geomechanics problems. Topics within the scope of interests include: development and validation of constitutive models that address coupling effects, discrete and continuum formulations for hydromechanics and thermo-hydro-mechanics problems, iterative sequential couplings of fluid and solid solvers, spatial variability of soil properties, multiscale mechanics, numerical enhancement techniques such weak and strong discontinuities, and regularization techniques to circumvent pathological mesh dependence.