Numerische Simulation und Analyse turbulenter Strömungen am Beispiel der Umströmung eines Zylinderstumpfes mit Endscheibe

The analysis of the dynamics in turbulent flows is still a major challenge due to the unsteady, three-dimensional and stochastic nature of turbulence. Overcoming this challenge is important, however, to characterise and quantify the properties of turbulence, so that desired and undesired effects such as strong mixing or increased drag, especially in technically relevant flows, can be identified, understood and possibly controlled. In particular, because of the spatial and temporal variation of turbulent flows, a method-based analysis is near-mandatory in order to extract at least the dominant effects semi-automatically in an industrial environment. In the present study, the flow around a finite wall-mounted cylinder, which is a prototype for various vehicle fittings or buildings and an example of a complex turbulent flow, has been numerically simulated with high resolution and analysed with respect to different perspectives. Employing traditional statistical analysis a topology for the time-averaged flow field could be obtained and seldom-documented flow features have been extracted and quantified. The extensive comparison of numerical and experimental flow data in this framework reveals consistently excellent agreement. The analysis of the fluid dynamics has been carried out using a combination of conceptually different analysis methods. Proper Orthogonal Decomposition, a newly-developed structure tracking algorithm and various filtering approaches are among the most important and successful techniques. The extraction of the dominant flow pattern, intermittency effects and instantaneous vortex formations was substantially simplified by these methods. Difficulties in the identification of individual phenomena arise from their interaction and synchronisation in the flow field. Nevertheless, much can be contributed to the understanding of the specific flow and the analysis procedures are evaluated with respect to their suitability for the analysis of turbulence.