Complex Wake Flows

• Applicants: Dr. Tobias Knopp; Professor Dr.-Ing. Rolf Radespiel; Dr.-Ing. Peter Scholz
• Subject Area: Fluid Mechanics
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 324552438

• Final Report Year: 2024

Final Report Abstract

Modern commercial transport aircraft use slotted flap systems for obtaining high lift coefficients during low-speed flight. The wakes of slats and main wings present in these configurations are subjected to the adverse pressure gradient, induced by the respective trailing wing element. The adverse pressure gradient generates a strong lateral increase of wake width and sometimes even embedded regions of reverse flow. This reduces the lift coefficient and limits maximum lift. Precise predictions of these effects are presently not possible as there is a lack of a trustworthy data base and hence, detailed validation of current flow models used in aircraft design is impossible. The objective of the present research project is to establish a comprehensive data base of wake flows at high Reynolds numbers with and without strong adverse pressure gradients. Turbulence resolving simulations and flow measurements by optical means generate the detailed balance of the Reynolds stress equations along the wake flow path. The turbulence data are used to extract the terms of the transport equation governing the turbulence length scale for the first time. The data base is used for physics-based extensions of a Reynolds-stress model of turbulence. Identification of the model extensions with a low model error and their calibration is accomplished by Uncertainty Quantification based on Bayesian Inference. The project spent significant efforts to validate the improvement of the Reynolds-Stress models for predicting the high-lift behaviour of a slotted wing section. The research leads to an improved agreement of simulations and experimental data for the three-element airfoil MD 30P-30N.

Publications

• A Wind Tunnel Experiment for Symmetric Wakes in Adverse Pressure Gradients. AIAA Scitech 2019 Forum. American Institute of Aeronautics and Astronautics.
  Breitenstein, Wiebke; Scholz, Peter; Radespiel, Rolf; Burnazzi, Marco; Knopp, Tobias; Guseva, Ekaterina; Shur, Michael & Strelets, Michael
  
• Experimental/Numerical Study of Turbulent Wake in Adverse Pressure Gradient. Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 401-412. Springer International Publishing.
  Guseva, E.; Shur, M.; Strelets, M.; Travin, A.; Breitenstein, W.; Radespiel, R.; Scholz, P.; Burnazzi, M. & Knopp, T.
  
• Numerical simulation of a turbulent wake subjected to adverse pressure gradient. Journal of Physics: Conference Series, 1400(7), 077046.
  Guseva, E. K.; Strelets, M. Kh; Breitenstein, W. & Scholz, P.
  
• Prediction Capabilities of Two Reynolds Stress Turbulence Models for a Turbulent Wake Subjected to Adverse Pressure Gradient. Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 565-575. Springer International Publishing.
  Burnazzi, Marco; Knopp, Tobias; Strelets, Michale Kh.; Shur, Michael L.; Travin, Andrey K.; Breitenstein, Wiebke; Scholz, Peter & Radespiel, Rolf
  
• Study of the Stagnating Flow in a Free Wake subjected to an Adverse Pressure Gradient, 13th International Symposium on Particle Image Velocimetry (ISPIV), Munich, Germany, July 22-24, 2019
  Breitenstein, W. & Scholz, P.
  
• Extending the kL equation of Rotta using LES data, WCCM- ECCOMAS Conference 2020
  Agbogwu, U., Guseva, E.K. & Radespiel, R.
  
• Curvature Correction for Turbulent Diffusion Inside a Differential Reynolds-Stress Model. Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 465-474. Springer Nature Switzerland.
  Ströer, Philip & Knopp, Tobias
  
• General Formulation of the Gradient Richardson Number for RANS Modelling. AIAA SCITECH 2023 Forum. American Institute of Aeronautics and Astronautics.
  Ströer, Philip & Knopp, Tobias
  
• Outer scaling of the mean momentum equation for turbulent boundary layers under adverse pressure gradient. Journal of Fluid Mechanics, 958.
  Wei, Tie & Knopp, Tobias
  
• Study of Richardson number in flows with mean-streamline curvature, In: 21st STAB-Workshop-Jahresbericht 2023, S. 160-161, 2023
  Vellala, S.L. & Knopp, T.
  
• The mean wall-normal velocity in turbulent boundary layer flows under pressure gradient. Journal of Fluid Mechanics, 975.
  Wei, Tie; Li, Zhaorui; Knopp, Tobias & Vinuesa, Ricardo
  
• RANS turbulence modeling validation and propects for improvement. Integration of computational and empirical experimentation techniques (invited), Panel discussion AIAA SciTech Orlando 8-12 January, 2024
  Knopp, T.
  
• Volumetric Reconstruction Of Stagnated Wake Structures In Adverse Pressure Gradient. Proceedings of the International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics, 21, 1-15.
  Lindner, Till Konstantin; Scholz, Peter; Breitenstein, Wiebke & Michaelis, Dirk