FOR 1182: Transport and Structure Formation in Turbulent Rayleigh-Bénard, Taylor-Couette and Pipe Flows near Solid Walls

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The description and understanding of turbulent flows is still one of the biggest challenges of engineering sciences and classical physics. The strong spatio-temporal fluctuations and couplings between flow structures at different scales in time and space limit the application of direct numerical simulations and require the modelling of turbulence in many practical situations. Only in some cases exact results can be obtained. Nearly all turbulent flows in nature and technology are bounded by solid walls. In their vicinity, strong interactions between differently sized structures dominate the dynamics. Starting with Ludwig Prandtls boundary layer concept, refined by symmetry arguments, many important results on mean profiles of turbulent field quantities have been obtained. Nevertheless, uncertainties in the mean profiles and scaling exponents, which are necessary for the calculation of global transport quantities, lead to variations in the predicted global transport that can vary by orders of magnitude. An important example is the heat transfer in thermal convection. Based on recent new insights and observations on the dynamics of turbulence near solid walls, our Research Unit will focus on the connection between local dynamical processes near the walls and global transport properties. Progress in understanding is expected by comparison of three fundamental flows that have been studied so far separately: thermal convection in a cell heated from below (Rayleigh-Bénard), shear turbulence between two concentric and rotating cylinders (Taylor-Couette) and pressure-driven turbulence in a pipe. Our investigations will improve the global transport laws. Furthermore, they open perspectives to control the turbulent dynamics in the vicinity of walls and to improve the modelling of complex flows in models with strongly reduced degrees of freedom.