Experimental investigation of turbulent superstructures in canonical boundary layers along flat plates with zero pressure gradient

• Applicant: Professor Dr. Christian Joachim Kähler
• Subject Area: Fluid Mechanics
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 316215356

The analysis of coherent flow structures in turbulent boundary layers along flat plates with zero pressure gradient is intensely studied due to the vast scientific and technological interest for this type of canonical flow. In particular, the discovery of highly ordered coherent fluid motions is very important as the complex turbulent exchange phenomena can be explained qualitatively taking the presence and interaction of these structures into account. In the literature, the presence of superstructures in turbulent boundary layers along flat plates with a zero pressure gradient is considered as universal. However several questions arise, namely, if a family of turbulent superstructures exists or if the turbulent superstructures observed in experiments are a superposition of individual large scale structures or if different superstructures exist depending on the intensity of the structures. Furthermore, the mechanism responsible for the generation and maintenance of the superstructures is under debate as well as the scaling with Reynolds and Mach number.Therefore, a canonical turbulent boundary layer flow along a flat plate with zero pressure gradient (ZPG) will be investigated at Reynolds numbers up to Re_θ=100,000 in the Atmospheric Wind tunnel Munich (AWM). Furthermore, the Trisonic Wind tunnel Munich (TWM) will be used to study the effect of Mach number on the coherent motions in a ZPG turbulent boundary layer between 0.3 < Mach < 3.0. High resolution 2D and 3D PIV/PTV measurement techniques will be applied to determine the size, shape and organization of the turbulent superstructures, their dynamics and mutual interaction and near their interaction with low-speed streaks near the wall and the surrounding flow field at high Reynolds and Mach numbers.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1881: Turbulent Superstructures