SPP 1881:  Turbulent Superstructures

• Subject Area: Thermal Engineering/Process Engineering ; Construction Engineering and Architecture ; Geosciences ; Computer Science, Systems and Electrical Engineering ; Mathematics ; Physics
• Term: since 2016
• Website: Homepage
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 273183002

The classical picture of turbulence is that turbulent fluid motion is characterized by a cascade of vortices and swirls of different sizes that give rise to a featureless and stochastic fluid motion. Our daily experience shows, however, that turbulent flows in nature and technology are often organized in prominent large-scale and long-living structures that can cause extreme fluctuations. The focus of the Priority Programme are Turbulent Superstructures, i.e., patterns whose coherence does not stop at the natural scale, such as the boundary layer height, but extends over much larger scales. The study of superstructures is now possible due to significant advances in measurement techniques, numerical simulation, and mathematical characterization. Tomographic laser-based measurement techniques can track the dynamics of turbulent structures with unprecedented resolution in space and time. Direct numerical simulations on massively parallel supercomputers have advanced to a level where turbulent flows in extended domains can be simulated at sufficiently high Reynolds numbers and in parameter ranges where superstructures emerge. Efficient methods to characterize dominant vortices and flow structures and to determine the transport across their boundaries as well as their dynamical evolution have been developed in applied mathematics. Computer science provides efficient algorithms for the visualization and fast processing of structures in very large data sets.The aim of the present Priority Programme is to integrate the different recent advances to arrive at a comprehensive characterization and understanding of turbulent superstructures. More detailed, this includes the experimental characterization of superstructures, direct numerical simulations of turbulent large-scale and superstructures, and their detection and identification by different Lagrangian and Eulerian methods. Furthermore, we want to analyse the origin of turbulent superstructures from primary and secondary instabilities, the role of symmetries and boundary conditions for their formation and dynamics. We want to understand their role for the turbulent transport, in particular that of their interfaces. Finally, we want to develop reduced models to describe their dynamics effectively and develop strategies to control these structures. In order to keep the program focused, it is intended to study singlephase, wall-bounded flows in simple Cartesian and parallel geometries, driven by shear or buoyancy. It is only by joining forces across the various disciplines that we will be able to achieve a better characterization of turbulent superstructures, to extract information about their essential properties and thus to obtain a comprehensive understanding of their impact on turbulence statistics and turbulent transport.

• DFG Programme: Priority Programmes
• International Connection: Australia, Netherlands, Spain, Switzerland, United Kingdom, USA

Projects

• Asymptotic Suction Boundary Layer: Alternative Linear and Weakly Non-Modal Stability Modes - a New Route to Large-Scale Turbulent Structures (Applicant Oberlack, Martin )
• Coherent superstructures in turbulent pipe and Taylor-Couette flows (Applicant Avila Canellas, Marc )
• Computational methods for coherent sets and coherent transport (Applicants Junge, Oliver ;  Karrasch, Daniel )
• Convection Cells in the Planetary Boundary Layer: Origin and Reduced Modeling (Applicant Mellado, Juan Pedro )
• Coordination Funds (Applicant Schumacher, Jörg )
• DNS and Visual Analysis of Superstructures in Turbulent Channels with Mixing by Parallel Injection (Applicants Theisel, Holger ;  Thévenin, Dominique )
• Effective Description of Superstructures in Turbulent Convection and Simple Turbulent Shear Flows (Applicant Wilczek, Michael )
• Experimental Analysis of Turbulent Superstructures in Thermal Convection by Time-Resolved Lagrangian Particle Tracking up to Very High Rayleigh Numbers (Applicant Bosbach, Johannes )
• Experimental investigation of superstructures in turbulent liquid metal convection (Applicant Vogt, Tobias )
• Experimental investigation of turbulent superstructures in canonical boundary layers along flat plates with zero pressure gradient (Applicant Kähler, Christian Joachim )
• Experiments on very large structures in fully developed turbulent pipe flow (Applicant Egbers, Christoph )
• How do turbulent superstructures interact with skin friction drag? (Applicant Frohnapfel, Bettina )
• Identification of transport-dominated large-scale structures in turbulent wall-bounded flows using a Characteristic DMD (Applicant Sesterhenn, Jörn Lothar )
• Investigations of the origin of turbulent superstructures in a flat-plate boundary layer with pressure gradient (Applicant Rist, Ulrich )
• Lagrangian and Eulerian analysis of superstructures in wall-bounded turbulence based on large-scale, time-resolved and volumetric measurements using Shake-The-Box and FlowFit (Applicant Schröder, Andreas )
• Lagrangian aspects of turbulent superstructures: numerical analysis of long-term dynamics and transport properties (Applicant Padberg-Gehle, Kathrin )
• Lagrangian coherent superstructures in buoyancy driven turbulence (Applicants Haller, Ph.D., George ;  Holzner, Ph.D., Markus )
• Manipulating structures & superstructures in turbulent Rayleigh-Bénard & Taylor-Couette flow with the help of stripy wall roughness. (Applicant Lohse, Detlef )
• Multi-Scale Visual Analysis of Superstructures (Applicant Westermann, Rüdiger )
• Nonlinear Fluctuating Hydrodynamics as Model for Turbulent Super-structures (Applicant Adams, Nikolaus Andreas )
• Numerical analysis of turbulent superstructures in thermal convection: Long-term dynamics by Lagrangian clustering and Markov state modeling (Applicant Schumacher, Jörg )
• Simultaneous volumetric measurement of the velocity and temperature field in Rayleigh-Bénard cells with large aspect ratio (Applicant Cierpka, Christian )
• Space-time methods for the computation and analysis of coherent families (Applicant Koltai, Péter )
• Superstructures and exact coherent states in the asymptotic suction boundary layer (Applicant Linkmann, Moritz )
• Superstructures and turbulent heat and momentum transport in inclined low-Prandtl-number convection (Applicant Shishkina, Olga )
• The influence of the large scale circulation on the transition to the "Ultimate state of thermal convection" (Applicant Weiss, Stephan )
• Turbulent superstructures in the turbulent cascade of Reynolds stresses (Applicant Gatti, Davide )
• Understanding and utilising relationships between coherent structures and almost invariant sets in function space (Applicant Dellnitz, Michael )

• Spokesperson: Professor Dr. Jörg Schumacher