Validation of CFD-based transition transport models to predict laminar-turbulent transition of swept transport aircraft wings

Abstract

Reducing the viscous drag of future commercial aircraft by means of laminar flow plays a key role in the transformation to climate-neutral aviation. To mitigate financial risks and to accelerate the design process of laminar aircraft, increasing use is being made of numerical methods, such as CFD. The applicability of CFD methods for the design process depends on a high degree of automation of the individual components and on the accuracy and reliability of the simulation results. In this respect, the design of laminar aircraft is particularly demanding for the CFD process. Streamline-based methods, based on linear local stability theory (LST) and the eN method or, more rarely, based on the non-local Parabolized Stability Equations (PSE) [2] offer a high degree of maturity and are therefore considered state-of-the-art. Although, these models have shown to be accurate and reliable, they require expert knowledge and automation is limited. At the same time, a new class of models for predicting laminar-turbulent transition is gaining attention. Transport equation transition models are based on information available locally (at the CFD node level), making them particularly well suited for automation and parallelization of 3D simulations with modern unstructured CFD codes. Despite the advantages these correlation-based transition models, the accuracy, robustness, and reliability of the models need to be ensured and demonstrated more extensively. This work contributed to the continuous development and validation of transition transport models, in particular the DLR γ-CAS model. The presentation will demonstrate the capabilities of the model to predict three-dimensional and transonic cases at high Reynolds number, compared to wind tunnel data. Furthermore, the inclusion of the effect of surface roughness into the model is discussed.