The demand for fast, high-fidelity, scale-resolving computational fluid dynamics (CFD) simulations is continuously growing. Especially new emerging aviation technologies, such as electrical vertical take-off and landing aircraft (eVTOL), strongly rely on advanced numerical methods to retain development life-cycle costs and achieving design targets more quickly. This paper presents a cutting-edge large-eddy simulations (LES) solver developed to enable over-night turnaround times for full aircraft simulations on advanced graphics processing unit (GPU) architectures. The solver models weakly compressible fluid flows over complex three-dimensional bodies based on an immersed boundary method with geometry-based and flow-based automatic mesh adaption. Its high accuracy and unprecedented performance is demonstrated for high Reynolds number aerodynamic benchmark cases and compared to recent results from literature. In addition, the successful validation against experimental data for the Lilium Jet canard is discussed.@en

We present and evaluate a two-phase model for Eulerian large-eddy simulations (LES) of liquid-fuel injection and mixing at high pressure. The model is based on cubic equations of state and vapor-liquid equilibrium calculations and can represent the coexistence of supercritical states and multi-component subcritical two-phase states via a homogeneous mixture approach. Well-resolved LES results for the Spray A benchmark case of the Engine Combustion Network (ECN) and three additional operating conditions are found to agree very well with available experimental data. We also address well-known numerical challenges of trans- and supercritical fluid mixing and compare a fully conservative formulation to a quasi-conservative formulation of the governing equations. Our results prove physical and numerical consistency of both methods on fine grids and demonstrate the effects of energy conservation errors associated with the quasi-conservative formulation on typical LES grids.

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We have developed a thermodynamically consistent and tuning-parameter-free two-phase model for Eulerian large-eddy simulations (LES) of liquid-fuel injection and mixing at high pressure. The model is based on cubic equations of state and vaporliquid equilibrium calculations. It can represent the coexistence of supercritical states and multi-component subcritical two-phase states via a homogeneous mixture approach without any semiempirical break-up and evaporation models. Computational results for liquid-fuel injection at transcritical operating conditions are found to agree very well with available experimental data for the ECN Spray A.@en

The coaxial injection of cryogenic nitrogen and warm hydrogen into a supercritical nitrogen atmosphere is studied numerically by means of well resolved large-eddy simulation (LES). Numerical data for two operating conditions are compared both quantitatively and qualitatively with a series of experiments [Oschwald et al., 35th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, 1999], A detailed thermodynamic analysis of phenomena associated with the binary mixing of nitrogen and hydrogen together with a systematic study of the thermodynamic state of cryogenic nitrogen prior to injection allows an assessment of uncertainties related to both numerical and experimental data. Trans- and supercritical mixing constitutes considerable challenges for numerical simulations with regard to physical modeling and numerical stability. We compare a fully conservative (FC) formulation to a quasi conservative (QC) formulation of the governing equation, which was recently proposed by Terashima and Koshi [J. Comput. Phys., 2012].

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We present numerical simulations of a reacting shock-bubble interaction with detailed chemistry. The interaction of the Richtmyer-Meshkov instability (RMI) and shock-induced ignition of a stoichiometric H2-O2 gas mixture are investigated. Different initial pressures in the range of po = 0.25-0.75 atm at a constant shock wave Mach number of Ma = 2.30 trigger different reaction wave types (deflagration and detonation). Low pressure reactions are dominated by H, O, OH production and high pressure chemistry is driven by HO2 and H2O2. The reaction wave type is crucial for the spatial and temporal evolution of the bubble. The RMI and subsequent Kelvin Helmholtz instabilities show a high reaction sensitivity. Mixing is significantly reduced by both types of reaction waves, with detonation waves showing the strongest effect.@en

We investigate a passive flow-control technique for the interaction of an oblique shock generated by an 8.8_∞ wedge with a turbulent boundary layer at a free-stream Mach number of M = 2.3 by means of large-eddy simulation. The control configuration studied combines suction applied inside the separation zone and injection acting upstream of the interaction region through a passive-channel concept. We present results for three configurations, which differ in the suction location within the recirculation zone while the injection position is kept constant. Besides the analysis of mean flow properties, the main focus lies on the turbulence evolution within the interaction region and the effect of the control devices on the low-frequency dynamics of the reflected shock movement.

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The transition process from regular to irregular shockwave/ boundary-layer interaction (SWBLI) at M_a = 2 is studied both numerically and theoretically. The classical two-and three-shock theory is applied for carefully analyzing a data base of well resolved large-eddy simulations (LES). Inviscid theory appears to be a descriptive tool for the interpretation of the highly transient flow field of the SWBLI. Disturbances related to the incoming turbulent boundary layer can be identified as a source of bidirectional transition processes between regular and irregular SWBLI at a critical deflection angle across the incident shock wave.

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