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.

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].

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.

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.