Fast iterative methods for solving the
incompressible Navier-Stokes equations
Carlos Echeverria Serur (COSSE student, double degree with
TU Berlin)
Supervisor: Kees Vuik
Site of the project: TU Delft
start of the project: December 2012
In March 2013 the
Interim Thesis
and a
presentation
has been given.
The Master project has been finished in August 2013
by the completion of the
Masters Thesis
and a final
presentation
has been given.
For working address etc. we refer to our
alumnipage.
Summary of the master project:
The numerical solution of the incompressible Navier-Stokes (N-S) equations is an area
of much importance in contemporary scientific research. Except for some simple cases,
the analytical solution of the (N-S) equations is impossible. Therefore, in order to solve
these equations, it is necessary to apply numerical techniques. The most commonly used
numerical discretization techniques include Finite Dierence Methods (FDM), Finite
Volume Methods (FVM) and Finite Element Methods (FEM). The discretization approach
followed throughout this thesis is done by the FEM. Due to the nonlinear character in
the behavior of fluids, the solution of the (N-S) system of equations requires a suitable
linearization of the algebraic system resulting from the FEM discretization of the original
system. The resulting linear system of equations gives rise to a so-called saddle-point
problem, an algebraic system which is nonsymmetric, indefinite, and typically ill
conditioned.
The efficient solution of this type of linear algebraic problem is a
challenge. The primary interest in these types of problems is due to the
fact that most of the computing time and memory of a computational implementation is
consumed by the solution of this system of equations. In this project we adopt an
iterative approach to solving this linear system, mainly by the use of a Krylov subspace
method combined with a preconditioned linear system of equations. In the case of the
Navier-Stokes problem, the type of preconditioners studied belong to a branch of Block
Preconditioners known as SIMPLE-type preconditioners (Semi Implicit Pressure Linked
Equations) in literature. These methods decouple the system and solve separate
subsystems of the velocity and pressure. The pressure subsystem arises from an appropriate
approximation of the Schur complement of the system.
In this work, we are interested in approaching the following questions arising from the
study of the saddle-point problem arising from the discretization of the Navier-Stokes
equations:
-
Why is there a stagnation phase in the iterative solution of the SIMPLE-preconditioned
Navier-Stokes algebraic system?
-
Why does the number of iterations increase for stretched grids?
Wake of a ship
Incompressible multi-phase flow
Contact information:
Kees
Vuik
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