Experimental/Numerical Study of Turbulent Wake in Adverse Pressure Gradient

Abstract

The paper presents a bilateral German-Russian project launched in 2017 and aimed at investigation of turbulent wakes in the presence of Adverse Pressure Gradient (APG). Such wakes are a common feature of high-lift wing flows near the maximum lift conditions (take-off and landing), when the wake of the main wing is subjected to APG created by flaps. This type of flow is known to be poorly predicted by available RANS models. Hence, an ultimate goal of the project is their improvement based on a detailed experimental dataset and on results of high-fidelity turbulence resolving simulations providing relevant second moment closure terms not accessible by measurements. After a brief overview of the experimental and numerical parts of the project, the paper focuses on the first zonal RANS-IDDES computations of a wake of the flat plate in APG created by a plane diffuser. These computations performed in the initial stage of the project (before obtaining experimental data) are aimed at evaluating the capability of this approach to ensure the required accuracy with reasonable computational resources. Results of the simulations conducted on 3 grids (18, 30, and 50 million cells) support the credibility of the approach and suggest that it ensures not only virtually grid-independent prediction of the mean flow characteristics of the wake but also the dissipation-rate which is a key quantity in the context of improvement of the Reynolds Stress Transport RANS models. This is achieved, despite a relatively large grid step in the wake region (about 75 Kolmogorov length scales), thanks to computing this quantity based on the balance of the separate terms of the Reynolds stress transport equations.