Plenary Lectures

Professor Charbel Farhat

A Computational Framework Based on an Embedded Method with Exact Local Riemann Solvers for Highly Nonlinear Multi-Phase Fluid-Structure Problems

Vivian Church Hoff Professor of Aircraft Structures, Department of Aeronautics and Astronautics, Department of Mechanical Engineering, and Institute for Computational and Mathematical Engineering,
Stanford University, USA

Abstract

This talk presents a computational framework for the solution of transient, highly nonlinear, high-speed, multi-phase fluid-structure interaction problems. To this effect, the context is set to that of the implosive collapse of a gas-filled underwater structure. This fluid-structure interaction problem is characterized by ultrahigh compressions, shock waves, large structural displacements and deformations, self-contact, and possibly the initiation and propagation of cracks in the structure. The development of a corresponding computational model is a formidable challenge. It requires accounting for all possible interactions of the external fluid — namely, water — the internal gas, and the given nonlinear structure. It also requires incorporating in the computations material failure models, and capturing the precise effects on the pressure peaks of many factors such as the rate of structural collapse, hydrodynamic instability at the fluid/bubble interface, and cavitation when it occurs in the external fluid. Many of these features also arise in the modeling of the extracorporeal shock wave lithotripsy procedure where shock waves are generated to break a kidney stone into small pieces that can travel more easily through the urinary tract and pass from the body. The key components of the described computational framework include: (a) an embedded multi-phase CFD (Computational Fluid Dynamics) method based on the exact solution of local, one-dimensional two-phase Riemann problems, (b) an effective tabulation and interpolation method based on truncated tensor products (sparse grid) for enabling the evaluation of the Riemann invariants and/or alleviating their computational cost, (c) an analytical approach for enforcing the kinematic transmission condition at the embedded fluid-structure interface, (d) an energy conserving algorithm for enforcing the equilibrium transmission condition at that same embedded interface, and (e) a staggered and yet numerically stable and time-accurate algorithm for efficiently time-integrating the coupled fluid-structure equations of equilibirum. Each of these computational topics is discussed in sufficient details with particular attention to achieving, wherever possible, second-order spatial and temporal accuracy. Finally, unique features of this computational framework are highlighted for several three-dimensional multi-phase fluid-structure interaction problems associated with underwater implosion.

Professor Ryutaro Himeno

Japan’s Next-Generation Supercomputer R&D Project and Grand Challenges in Life Science

Deputy Program Director of Program for Computational Science, Group Director of Integrated Simulation of Living Matter Group, Director of Advanced Center for Computing and Comunication
RIKEN (The Institute of Physical and Chemical Research), Japan

Abstract

MEXT and RIKEN started the Next-Generation Supercomputer R&D Project in 2006, of which goal is to develop a supercomputer with 10 Peta FLOPS in 2011FY. The supercomputer is to use a newly developed SPARC chip connected by improved 3D torus network. In this R&D project, not only hardware development but also software development in Nano Science and Life Science as Grand Challenge problems are planed and included. The Institute of Molecular Science leads the Nono Science Grand Challenge and RIKEN leads the Life Science one.

As the Life Science Grand Challenge, we have two approaches to achieve comprehensive understanding of life phenomena and to contribute to our society by creating medicine and developing medical/surgical treatment. Those approaches are 1) theoretical simulation approach and 2) data-driven approach. In addition to these approaches, we have a HPC team which is responsible to deliver maximum performance of the 10 Peta FLOPS supercomputer to tune the application software and to develop and provide tools for visualization and parallelization to other teams. These software tools are also available to anyone who will use the supercomputer.

Current status of supercomputer development and the application software development in Life Scinece will be shown in the talk.