Session: Poster Session

Paper Number: 160468

The Benefits of Selecting Anisotropy Resolving Turbulence Models for Predicting Flow in Highly-Bent Serpentine Aircraft Intakes 

Serpentine ducts are commonly used as intakes of modern low-bypass aero-engines, and they allow for atmospheric air to be drawn through to the aero-engine installed in the aircraft fuselage. These ducts are diffusers that are designed to slow airflow before the compression stages of the aeroengine, and they are highly bent to remove a direct line of sight from the exterior of the aircraft to the aeroengine. The performance of the compressor stages are coupled to the upstream flow features that develop in the intake, and this coupled system requires thorough analysis over the entire flight envelope. Serpentine ducts feature smooth surface curvature and strong pressure gradients that cause unsteady vortex formation and flow separation. These large upstream flow features are ingested by the engine, significantly reducing the performance of the compression stages. Quantifying the performance of such a complex system requires a study of five parameters - namely Reynolds number, Mach number, engine mass flow rate, as well as the angles of attack of the aircraft - and RANS calculations are commonly used to undertake such complex parametric study. Industrial eddy-viscosity turbulence models are fundamentally inappropriate for the study of such a complex system (Gerolymos et al., 2010). This is because eddy-viscosity models do not allow for misalignment between the Eigenvectors of the mean-strain-rate and Reynolds-stress tensors, meaning that such models offer a poor description for anisotropic turbulence. Such models also provide a poor description of turbulent kinetic energy production of the flow, and this is because of the limited description of the Reynolds-stress tensor. In the present work, we consider three classes of turbulence model; namely an eddy-viscosity model, an explicit algebraic Reynolds-stress model, as well as a differential Reynolds-stress model. Each model represents a different underlying modelling philosophy and assumptions made in model development. The k-omega SST of Menter (1994) represents a commonly used eddy-viscosity model, which acts as an industrial reference case in our comparisons. The explicit algebraic Reynolds-stress model is represented by the work of Wallin and Johansson (2000), which accounts for misalignment of the Eigenvectors of the Reynolds-stress and mean-strain-rate tensors with an algebraic anisotropy model. Finally, we consider the elliptic blending differential Reynolds-stress model of Manceau and Hanjalić (2002). While all differential Reynolds-stress models allow for the transportation of the Reynolds-stress anisotropy and have exact turbulent kinetic energy production, the additional benefit of the elliptic blending model (Manceau and Hanjerlic, 2000) is that the model can be integrated into the viscous sublayer. We assess the performance of the three models on a highly-bent serpentine intake benchmark known as the military engine intake research duct (MEIRD), which was developed at the University of the Bundeswehr Munich. We assess the elliptic blending equation and the pressure-strain correlation in the near-wall region, and study the experimental pressure measurements throughout the intake system. This work highlights future modelling opportunities and improvements across all classes of model.

Presenting Author: Sean Hanrahan The University of Melbourne

Presenting Author Biography: Sean is a final year PhD candidate at the University of Melbourne (Australia). His research specialises in physics-informed machine learning and turbulence modelling for industrial applications, with a focus in developing algorithms that are constrained to the known physics of wall-bounded turbulence. Sean currently studies advanced Reynolds-stress turbulence models in serpentine ducts, with a keen interest in the pressure-strain correlations of the near-wall region.

Authors:

Sean Hanrahan The University of Melbourne
Julian Scheibel Institute of Jet Propulsion, University of the Bundeswehr Munich
Andreas Grois Institute of Jet Propulsion, University of the Bundeswehr Munich
Marcel Stößel Institute of Jet Propulsion, University of the Bundeswehr Munich
Melissa Kozul The University of Melbourne
Suad Jakirlić Institute for Fluid Mechanics and Aerodynamics, Technical University of Darmstadt
Dragan Kožulović Institute of Jet Propulsion, University of the Bundeswehr Munich
Richard Sandberg Department of Mechanical Engineering, The University of Melbourne