Research Group 3: Scientific Computing

Secretariat
Kollegiengebäude Mathematik (20.30)
Room 3.039

Zimmer 3.039
Englerstr. 2
Kollegiengebäude Mathematik (20.30)
76131 Karlsruhe

Karlsruher Institut für Technologie (KIT)
Fakultät für Mathematik
Institut für Angewandte und Numerische Mathematik
Arbeitsgruppe 3: Wissenschaftliches Rechnen
Englerstr. 2
Kollegiengebäude Mathematik (20.30)
D-76131 Karlsruhe

Office hours:
Mon-Thu 9-12 Uhr

Tel.: +49 721 608 42062

Fax.: +49 721 608 43197

# Seminar (Highly oscillatory problems) (Winter Semester 2017/18)

 Lecturer: JProf. Dr. Katharina Schratz Seminar (0126400) 2

The topics of the seminar will be discussed in a first meeting on Monday, 16.10.2017, at 15:45 in room 2.058 (Math Building 20.30).

We recommend this seminar to Master students and also late Bachelor students who have already attended lectures on the (numerical) analysis of differential equations.
Programming skills in MATLAB are recommended.

It will take place as a block seminar on one or two days in January 2018.

 Seminar: Monday 16.10.2017 15:45 First Meeting en-block class SR 2.058 (Building 20.30) Block Seminar in January 2018 en-block class
 Lecturer JProf. Dr. Katharina Schratz Office hours: By Appointment Room 3.024 Kollegiengebäude Mathematik (20.30) Email: Katharina.Schratz@kit.edu Dr. Patrick Krämer Office hours: by appointment Room 3.025 Kollegiengebäude Mathematik (20.30) Email: patrick.kraemer3@kit.edu

# Motivation

Consider a (linear) harmonic oscillator (a pendulum consisting of a spring with a mass)

with exact solution (deviation of the mass from the equilibrium at time ).
Small values of thereby belong to nonstiff springs and slow oscillations, whereas large belong to stiff springs and rapid oscillations. For large the latter example describes a highly oscillatory problem (see link to a simulation movie below).

Harmonic oscillator with

• a nonstiff spring with (green, left)
• an intermediate spring with (yellow, middle) and
• a stiff spring with (red, right)

# Seminar Content

Motivated by this linear example, in this seminar we treat linear and nonlinear highly oscillatory problems. Due to the rapid oscillations, standard time integration schemes, such as explicit Euler, Störmer-Verlet and related Runge-Kutta type methods, only allow very small time steps in order to guarantee stability of the exact solution. This leads to huge computational costs.

The aim of this seminar is to discuss the construction and analysis of methods which can cope with the rapid oscillations and thus allow to overcome these numerical challenges.

# References

E. Hairer, C. Lubich, G. Wanner: Geometric Numerical Integration. Structure-Preserving Algorithms for Ordinary Differential Equations. 2nd Edition. (Springer 2006)