The English-written dissertation "Validated numerical simulation of fluid-structure interactions of bridge girders in turbulent wind fields" by Dr.-Ing. Anina Sarkic, Belgrade/Serbia, deals with the scientifically and technically extremely demanding and complex subject area of fluid-structure interactions. In her work, she investigates the very complex aeroelastic behavior of vibrating bridge superstructures and identifies critical instability points. The research is motivated not least by the major task facing the public sector and the construction industry in view of the upcoming renewal of numerous highway bridges in Germany as part of the replacement of deteriorated prestressed concrete structures from the 1960s and 1970s and the upgrading of traffic routes due to the increase in road-bound freight traffic. As part of the approval planning for bridge structures, the aeroelastic stability of a bridge structure must always be verified. However, as a result of the continuing trend towards the development of very economical construction methods, verification problems for the structural condition have frequently arisen in recent times. It is not surprising that this particularly affects bridge girders in the state of advancement in view of advancement widths of often 100 m and sometimes considerably more. Using selected methods of computational fluid dynamics, Dr.-Ing. Sarkic is developing a simulation method which, in addition to the mean and turbulent flow effects, reproduces in particular the local motion-induced interactions on bridge structures oscillating in the wind. First simulations of turbulent flows are solved on the basis of RANS (Reynolds-Averaged Navier-Stokes) and URANS (Unsteady RANS) methods. For building aerodynamic problems, so-called High-Re (High Reynolds Number) formulations and turbulence models are used, e.g. the LLR-k-ω model. The doctoral student achieves the decisive breakthrough through the precise results analysis of several extended measurement series (Fig. 1) in the Bochum boundary layer wind tunnel. The validation of the simulation results against the experimentally found reference data reveals the important influence of strongly unsteady flow separations from the oscillating bridge cross section. Motivated by this, the computational method is extended by high-resolution simulations using the large-eddy simulation (LES), but this involves a high computational effort (Fig. 2). To be able to reduce this by local adaptation of the computational grids and the flow solvers is another decisive research result of the work.

This text appeared in Newsletter 2014-2. The entire newsletter can be downloaded from the homepage of the Faculty of Civil and Environmental Engineering. Zur Homepage der Fakultät für Bau- und Umweltingenieurwissenschaften