Investigation of turbulent boundary layers with pressure gradient at high Reynolds numbers with high resolution multi camera techniques

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In this research project, the influence of a positive streamwise pressure gradient and a beginning separation on large scale turbulent structures will be investigated. Further, the interaction between the large scale turbulent superstructures in a boundary layer's outer part and the small near-wall coherent turbulent structures will be investigated experimentally. The impact of large scale structures and different pressure gradients on local reverse flow events will be analysed as well. If there is a connection between local reverse flow events and the appearance of large, global flow separations is another research question that will be investigated within this project. Because of the large range of scales which must be resolved in order to answer this questions, a measurement technique concept is required which allows for the simultaneous resolution of the small scales near the wall and the large scale superstructures that elongate over several boundary layer thicknesses. Since a considerable amount of equipment and knowledge is required to accomplish this task, the analysis demands a cooperation between the Universität der Bundeswehr München and the DLR Göttingen. The answer to the scientific question will enhance the physical understanding of the interaction between the different turbulent scales. In addition, advanced time resolved 3D-PTV techniques will be utilized in large fluid volumina to get a 3D picture of a turbulent boundary layer and large scale structures including their surrounding flow.While many investigations have been performed at low Reynolds numbers in the past, the technical relevant flow conditions will be of interest. Since this is only possible in wind tunnels with long test sections, the experiments will be performed in the 22 meter long test section of the atmospheric wind tunnel at the Universität der Bundeswehr München.