### Motivation

Along with the development of large aircraft, such as the Airbus A3XX, **aeroelasticity ** and its
consideration in the design process becomes ever more important. As an example that can be given serves the
flutter of big, flexible wings. The flutter-onset occurs early and has thus to be predicted accurately.

Since experimental investigations are expensive and computer resources get cheaper reduction in
experimental effort due to efficient and accurate computational simulations might lead to crucial
competitive advantages.
**Under these viewpoints the capabilities of the CFD-software developed at HFI is enhanced to
CSM (Computational Structure Mechanics) so that both problems can be solved for simultaneously.**
In the first step this work is confined to **2D-phenomena** in the context of the BRITE-EURAM
research project UNSI
where an **iterative coupling using the same method for both problems** is aimed at.

### Approach

Fluid- and structure mechanics are governed by the same conservation-equations
for mass, moment and energy, but in practice the numerical schemes mostly applied are fundamentally
different.
Our basic approach is to use numerical methods for simultaneous solution of aerodynamic and structure mechanic problems
based on the **Finite Volume Method (FVM)** for block-structured grids with non-matching block-interfaces.
Moving and deforming grids are implemented obeying the Space Conservation Law (SCL). It was already shown
that the Finite Volume Method can be used to capture elasticity-problems [1,2,3].

The CFD-software is an implicit procedure of
second order accuracy. Complex goemetries and local mesh refinements can be
handled by semi-structured grids on the basis of general curvilinear
coordinates. The cartesian velocity components as well as all further
variables are stored in the control-volume centers. Diffusive terms are
approximated applying central difference schemes whereas convective
terms are approximated by monotonous, limited functions of higher order.
The governing equations are solved sequentially, where a pressure-correction
algorithm of the SIMPLE type is carried out to ensure mass conservation.

### Results

The first results of coupled computations have been obtained during UNSI for a flexible but inextensible sail [4], which has
been modelled as a chain to compute the sail shape.

### Current Research Projects

Within the DFG-Project (TH 288/29-2) investigationens about the dead-space-ventilation in animal models with acute lung injurie are carried out.

Protektive Beatmung Quantitative analysis of dead-space-ventilation in animal models with acute lung injurie.

In a french-german collaboration between TU Berlin and Aix-Marseille
Université, the aerodynamics of flapping insect flight is investigated

Numerical investigation of insect flight

** References **

[1] __Bunge, U:__ *Die Behandlung der Strukturmechanik mittels der FV-Methode*, Internal report 01/99, Hermann-Föttinger Institut, TU Berlin, April 1999, only available in German

[2] __Demirdzic, I.; Muzaferija, S.:__ *Finite Volume Method for Stress Analysis in Complex Domains*, Int. J. f. Num. M. in Eng., Vol. 37, 1994

[3] __Demirdzic, I.; Muzaferija, S.:__ *Numerical Method for Coupled Fluid Flow, Heat Transfer and Stress Analysis using Unstructured Moving Meshes with Cells of Arbitrary Topology*, Comput. Methods Appl. Mech. Engrg., Vol. 125, 1995, pp. 235-255

[4] __Bunge, U.; Rung, T.; Thiele, F.:__ *A two-dimensional sail in turbulent flow*, Fluid Strucrure Interaction, Chakrabarti, S. K.; Brebbia, C. A. (Eds.), pp. 245-254, Series: Advances in Fluid Mechanics, Vol. 30, WIT Press, Southampton, Boston, 2001, ISBN 1-85312-881-3, presented by Bunge, U. on Fluid Strucrure Interaction 2001 in Chalkidiki, Greece, September 2001

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Last modified: Thu Nov 1 15:34:36 CET 2001