OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Space Technology The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Develop computational efficient models for heat transfer prediction in 3D time-resolved LES (large eddy simulation) and/or uRANS (unsteady Reynolds averaged Navier-Stokes) simulations of rotating detonation rocket engines (RDRE). DESCRIPTION: Rotating Detonation Rocket Engines (RDRE) are a disruptive new rocket engine technology under development by the Air Force Research Laboratory's Aerospace Systems Directorate Rocket Propulsion Division at Edwards AFB California since 2017. The propulsion technology has the potential to deliver a distinct military advantage by significantly improving the size, performance, stability, and unit cost of liquid rocket engines over the existing state of the art constant pressure rocket engine technology in use throughout the space industry. Analyses of the impacts of the propulsion improvements show RDREs deliver a distinct military advantage for specific Military/Dual Use applications of interest to DoD. Potential applications include orbit transfer vehicles (OTV). The environment inside a rotating detonation rocket engine (RDRE) is a high-temperature environment confined to a narrow annulus. The local flow is constantly modulated by high-frequency high-pressure high-temperature detonation waves. Obtaining accurate measurements of heat transfer in these devices is difficult. Typically, only limited calorimetry data is available which makes identifying local peak regions impossible. Simulations of RDREs are very costly, the nature of the non-premixed flow field makes it impossible to simplify the geometry. The entire 360 geometry is required including the discrete injectors. These unsteady simulations can cost a million CPU hours for uRANS (unsteady Reynolds averaged Navier-Stokes) or a few million CPU hours for LES (large eddy simulation). These simulations almost always include adiabatic wall boundary conditions which provide no information on the local heat transfer. The USAF is interested in improved tools that can work with existing uRANS and LES codes to better model and predict the heat transfer in these devices. Conjugate heat transfer (CHT) is one tool that meets the technical requirements of this effort but is cost prohibitive when fully coupled to a 3D time-resolved simulation. CHT provides a way to model the reacting flow in the annulus and the conduction in the walls without an assumption on the interface condition between the walls and the fluid. The slow time scales associated with conduction make this cost prohibitive in a fully coupled operation. Another issue is the resolution of the boundary layer inside the fluid domain. Many RDRE simulations avoid the resolution of the boundary layer to reduce the cost. The boundary layer is key for the heat transfer. A tool to overcome this is a wall model which approximates the boundary layer in the unresolved simulation. These wall models typically rely on assumptions which are violated in the RDRE like fully developed flow, or non-reacting flow. The USAF is looking for creative solutions to this problem. The desired outcome is the development of models that provide predictions for the heat transfer in an RDRE at lower cost compared to a fully coupled 3D unsteady LES/CHT solution. These can include, but are not limited to, Novel wall models for RDRE flow conditions Acceleration and cost reduction techniques for conjugate heat transfer in transient simulations New boundary conditions that approximate the key physics from a LES/CHT Reduced order models for the solid wall state that couple with the LES The final solution must be scalable to HPC (high-performance computing) applications and be easily integrated with existing MPI based FORTRAN/C++ reacting flow LES codes through libraries with well-defined API's or provided analytical models. Delivery of the source code to the government is required. The thermal prediction capability enabled by delivered engineering-level models for RDRE heat flux will significantly accelerate the engineering development timelines required to transition RDREs for specific applications and reduce the current hardware intensive test-fail-fix approach. This will allow more rapid and low-cost transitions of RDRE technology to the warfighter for several planned applications. PHASE I: The goal of the phase one is to formulate an initial plan to solve this task. The plan should include initial studies and enough background work to lower the risk for the proposed solution which will be executed in the phase two effort. Document the scientific/technical suitability and merit of the proposed solution to the problem. A clear description of the assumptions and approximations made in the development of the model. Development of a task and execution plan for the Phase II. Optional Initial simulations of surrogate flowfields that validate the approach. PHASE II: The phase two should be used to develop the software library and provide validation that it is providing useful results. This software library will be used to overcome key limitations in traditional simulations. Complete development of the model started under the phase I effort. Complete documentation of the theory and implementation of the model. Complete documentation of the API used for any provided model. Demonstration of the validation of the model in an unsteady RDRE simulation, gas-gas, or liquid-gas. Delivery of the library with source code. PHASE III DUAL USE APPLICATIONS: A potential phase III extension is to further develop/transition this code into a commercial or government design tool that can be used to design and evaluate cooling methodologies for RDRE's. REFERENCES: 1. Batista, A., Kickliter, T., Ross, M., Harvazinski, M. E., & Paulson, E. J. (2024). Computational Study of Chamber Wall Thermal Effects and Heat Flux in a Rotating Detonation Rocket Engine. In AIAA SCITECH 2024 Forum (p. 2430).; 2. Hou, Y., Cheng, M., Sheng, Z., & Wang, J. (2024). Unsteady conjugate heat transfer simulation of wall heat loads for rotating detonation combustor. International Journal of Heat and Mass Transfer, 221, 125081.; KEYWORDS: Rotating Detonation Engine; Rotating Detonation Rocket Engine; RDE; RDRE; Heat Transfer; Conjugate Heat Transfer; Numerical Modeling; CFD; Numerical Heat Transfer; CHT
