Simulation of High-Speed Turbulent Combustion
Hypersonic air-breathing propulsion systems were first envisioned about six decades ago. The successful flights of the NASA X-43 and the recent partial success of the Air Force X-51A demonstrate that these systems can work. The engines in these vehicles are mechanically extremely simple, compared to turbofans or even automobile internal combustion engines. However, the coupled fluid dynamics and chemical energy conversion that takes place inside these engines is anything but simple. Almost every non-linear fluid dynamics phenomenon plays a role in their operation: turbulent boundary layers, free shear layers, shock waves, fuel-air mixing, and finite-rate chemical reactions all interact with one another in an extremely dynamic and energetic environment. The Candler research group is developing novel large-eddy simulation (LES) approaches to simulate these complex flows. LES simulations resolve the large-scale unsteady turbulent motion and model the unresolved subgrid-scale motion. This approach has been shown to correctly represent complex geometry turbulent motion for a wide range of applications. However, appropriate numerical methods and subgrid-scale models have not been developed and validated for the highly compressible conditions that characterize the high-speed combustion systems. The group has recently developed a novel subgrid modeling approach, along with associated improvements to the numerical methods. Thus, they are using MSI computer resources to simulate experimental configurations and compare the simulations with the available experimental data.
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