MAC Seminar, speaker Fred Wubs (RUG)

Date: Tuesday 22nd November 2016
Time: 15.00 - 16.00hrs
Room: L120, CWI

Name: Fred Wubs, University of Groningen, http://www.math.rug.nl/~wubs/
Title: HYMLS: A robust multilevel solver for 3D steady flow problems

Pseudo-arclength continuation is a powerful technique for investigating
parameter sensitivity
of complex dynamical systems. However, for three-dimensional fluid
dynamics problems the application of this technique
is difficult
because of the ill-conditioned Jacobian matrices that arise during the
process.
The indefiniteness of the matrices and the
computational complexity makes direct solvers inefficient in 3D, while
iterative solvers typically lack robustness at
high Reynolds numbers.

In the talk we first will discuss general direct and iterative
approaches to solve linear systems. Next we will
indicate the special properties of the system of equations arising from
the finite volume discretization of the incompressible
Navier-Stokes equations and the difficulties this gives in solving them.  
Finally, we present the hybrid direct/iterative solver HYMLS for the
Jacobian of the incompressible Navier-Stokes equations on
structured grids.
Among others, we will show results of computations on a 3D lid driven
cavity near the first Hopf bifurcation.