Description: The innovative methodologies proposed in this STTR Phase 1 project will enhance Loci-STREAM which is a high performance, high fidelity simulation tool already being used at NASA for a variety of CFD applications. This project will address critical needs in order to enable fast and accurate simulations of liquid space propulsion systems (using propellants such as LOX, LCH4, RP-1, LH2, etc.). The proposed enhancements to Loci-STREAM in this project are: (1) Level-Set methodology (which will be of high fidelity and highly scalable for massively parallel computing) for tracking liquid propellant interface for primary atomization, and (2) Adaptive tabulation for flamelet models for turbulent combustion designed for distributed parallel computing architectures. The following methodologies are already available in Loci-STREAM: (a) Lagrangian particle tracking for motion of droplets, (b) Droplet evaporation model, and (c) Flamelet models in Hybrid RANS-LES framework for unsteady turbulent combustion. Integration of the methodologies proposed in this project into Loci-STREAM will result in a state-of-the-art multiphase combustion modeling tool which will enable fast and accurate design and analysis of liquid rocket engine flow environments, combustion stability analysis, etc. which constitute critical components of space propulsion engines that are part of NASA's Space Launch System (SLS).

Benefits: The outcome of the proposed Phase 1 and Phase 2 research and development activities will be a powerful and advanced version of a CFD-based multiphase combustion code (called Loci-STREAM) for propulsion engines at NASA. This code is envisioned to be a powerful design and analysis tool for propulsion devices including full rocket engine simulations, injector design, etc. This tool will have a direct impact on development of propulsion systems relevant to the SLS by enabling design improvements of injectors involving liquid propellants such as LOX, LH2, LCH4, RP1, etc. Specific applications at NASA of this capability will include: (a) Fast and accurate simulation of turbulent combustion in existing or new/modified liquid space propulsion engines including J-2X, RS-68, F-1, etc., (b) Fast and accurate 3D unsteady simulations of multi-element injectors coupled with fuel and oxidizer feed lines and manifolds which will yield high-fidelity information for combustion instability models, (c) Prediction of stability and stability margins, (d) Design of acoustic cavities for combustion stability, etc.

The computational tool resulting from this project will have wide-ranging commercial applications. The Hybrid RANS-LES (HRLES) methodology can be used for a wide variety of engineering applications involving unsteady turbulent flows. The high-fidelity turbulent combustion simulation capability will lead to improved analysis of unsteady turbulent reacting flow fields in gas turbine engines, diesel engines, etc. leading to design improvements. The real-fluids methodology can be used in a large number of industrial flow situations involving both chemically inert and reacting flows. With additions of multi-phase combustion modeling capability, the applicability of this tool can be further broadened.