Numerical simulation

Numerical Approximation of Nematic Fluids

Friday, January 19, 2018 - 9:00am - 9:50am

Noel Walkington (Carnegie Mellon University)

Slides of Presentation

This talk focuses on the issues that arise when modeling and
simulating fluids containing rod--like molecules (nematics). The
(average) orientation of these fluids is typically modeled by a unit
vector field which complicates both the analysis and numerical
solution of these equations. In particular,

i) The unit length constraint gives rise to topological
singularities. While singularities are observed ubiquitously in
liquid crystals, classical models assign infinite elastic
energy to these configurations.

Coupled atmosphere - wildland fire numerical simulation by WRF-Fire

Thursday, December 2, 2010 - 2:45pm - 3:30pm

Jan Mandel (University of Colorado)

pdf presentation - no movies, 13MB

WRF-Fire consists of a fire-spread model, implemented by the level set method, coupled with the Weather Research and Forecasting model (WRF). In every time step, the fire model inputs the surface wind and outputs the heat flux from the fire. The level set method allows submesh representation of the burning region and flexible implementation of various ignition modes. This presentation will address the numerical methods in the fire module, solving the Hamilton-Jacobi level set equation, modeling real wildfire experiments, and visualization.

Dealing with Stiffness in Low-Mach Number Flows

Friday, October 3, 2008 - 1:25pm - 2:25pm

Caroline Gatti-Bono (Lawrence Livermore National Laboratory)

Numerical simulation of low-Mach number flows presents challenges because of the stiffness introduced by the disparity of time scales between acoustic and convective motions. In particular, the acoustic, high-speed modes often contain little energy but determine the time step for explicit schemes through the CFL condition. A natural idea is therefore to separate the acoustic modes from the rest of the solution and to treat them implicitly, while the advective motions are treated explicitly or semi-implicitly.