Numerical study of the compressible turbulent asymptotic suction boundary layers

• Applicant: Dr.-Ing. Christoph Wenzel
• Subject Area: Fluid Mechanics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 536555758

In the very limited set of canonical test cases available for fundamental research of boundary layers, the case of the asymptotic suction boundary layer represents an exceptional candidate. Due to the simultaneous presence of a far-field boundary condition of a free flow in conjunction with a time-averaged constant boundary layer thickness, this case can be considered as a direct link between spatially evolving boundary layers and channel flows, on which most of the fundamental research is based. Furthermore, the case of the turbulent asymptotic suction boundary layer (TASBL) represents the simplest case of a free boundary layer with suction and is thus the case that allows the most meaningful statements about the principle influence of wall transpiration on the structure of a turbulent boundary layer in general. Against this background, it is surprising that no attention has been paid to the compressible TASBL in the past (at least to the author's knowledge) since the possibilities offered by this case are unique in many respects. Therefore, it can be considered a success of the preliminary work carried out by the authors during the last year to prove by means of direct numerical simulation (DNS) that the TASBL, whose existence has so far been proven exclusively for incompressible flows, also exists in the compressible regime. Although only two preliminary DNS were performed on a comparatively coarse computational grid, a first understanding of the most important features of compressible TASBLs has been gained. Based on this understanding, the main objective of the present proposal is to characterize the compressible TASBL over a sucked adiabatic wall for the first time and to evaluate the effects of different suction ratios and Mach numbers. By investigating this highly specialized class of flows, it is further intended to discuss fundamental questions concerning both fundamental compressibility concepts, the structure of compressible turbulent boundary layers, and fundamental questions about the influence of wall transpiration on compressible turbulent boundary layers in a meaningful way. Subsequently, taking direct advantage of the bridge-building character of the TASBL, the first steps are taken to transfer the conclusions drawn from the TASBL to the spatially evolving compressible turbulent boundary layer.

• DFG Programme: Research Grants