High-Fidelity Computational Modeling of Fluid-Thermal-Structural Interactions in Hypersonic Air-Breathing Systems

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Computing and Software;Hypersonics OBJECTIVE: Develop robust, accurate, and efficient computational methods for predicting the coupled fluid-thermal-structural response of an air-breathing hypersonic system at moderate hypersonic speeds. DESCRIPTION: Air-breathing hypersonic systems are typically powered by ramjet or scramjet engines. At hypersonic speeds (i.e., Mach 5+), compression of the air stream is performed without any turbomachinery simply by slowing the oncoming flow through an isentropic (i.e., minimal loss) compression and/or a series of oblique shock waves. For scramjet engines, designing an inlet, which provides uniform flow to the combustor with minimal aerodynamic losses, is critical to obtaining high-engine performance (e.g., high-inlet efficiency, high-combustion efficiency, thrust). In addition to engine performance, the design of scramjet inlets significantly influences engine operability. At off-design conditions, the contraction ratio of the inlet may cause strong shock waves to develop that can prohibit mass flow through the engine and ultimately expel the flow out the front of the engine leading to engine unstart . Unstart can be catastrophic to the performance of a hypersonic system. Once an engine has unstarted, it is very difficult, if not impossible, to restart the engine in flight. Furthermore, due to the dynamics of the unstart process, maintaining control of the vehicle can be challenging and often leads to system failure. In the hypersonic environment, the aerodynamics through the engine become increasingly coupled with the structural and thermal response of the vehicle. Vehicle deformation, both structural deformation and thermal deformation, can have significant impacts on the performance and operability of the propulsion system. To date, conventional design and analysis methodologies utilize isolated assessments of each physics domain (e.g., aerodynamics, structures, and thermodynamics) and do not properly capture the coupled effects between physics domains (e.g., fluid-thermal-structural interaction). If multiphysics interactions are not properly captured and accounted for during the design phase, the resulting hypersonic system may have reduced mission performance or may experience an unstart event leading to system failure. Improvements in high-fidelity modeling and simulation of the fluid-thermal-structural response of a hypersonic vehicle are desired. The computational methods that are developed should address the impacts of coupling strategies between physics domains on the resultant simulation time and modeling fidelity for air-breathing hypersonic vehicles at moderate hypersonic speeds. The methods and tools shall be validated against experimental data and be capable of accurately accessing engine, air vehicle, and material/structural performance during flight. Any developed methods should be capable of transition and integration into government toolsets. PHASE I: Develop and implement robust multiphysics coupling methodologies to simulate the coupled fluid-thermal-structural response of a body at moderate hypersonic speeds. Review the robustness, computational cost, and accuracy of coupling strategies for high-fidelity multiphysics simulation. Coordinate with government POCs on interface design to ensure the developed methodology can transition into government toolsets (e.g., CREATE-AV Kestrel). Validate the coupled multiphysics simulation capability against existing experimental data where the coupling of either fluid-structural, fluid-thermal, or fluid-thermal-structural interaction is captured. Assess the accuracy and computational cost of various multiphysics coupling strategies relative to conventional, single-physics analyses. The Phase I effort will include prototype plans to be developed under Phase II. PHASE II: Demonstrate the coupled multiphysics simulation capability for a Navy-relevant, air-breathing, hypersonic vehicle. Assess the design impacts and improvements realized by the coupled multiphysics simulation capability relative to existing approaches. Further enhance the robustness, accuracy, and efficiency of the methodology. Continue coordination with government POCs to ensure an effective transition to government toolsets. Any developed methodologies should be able to execute on conventional CPU-based high-performance computing (HPC) hardware. Deliver prototype software tools on HPC, and document the mathematical theory, assumptions, and guidance for tool execution. Conduct a training session for potential government users on the new capability. PHASE III DUAL USE APPLICATIONS: Verification and validation (V&V) of the new methods based on available test data. Methods should be updated based on the V&V effort. Additional analyses should be performed on a Navy relevant configuration. Developed algorithms and code are sufficiently validated to transition to HPCMP CREATE-AV for integration. With the push for commercial aircraft operating at hypersonic speeds now part of the national discussion, the tools and methods developed under this STTR topic will have utility to the design and development of future commercial hypersonic and reusable space access platforms. Additionally, developments from this work can be applicable to computational analysis of supersonic and subsonic reacting flows. REFERENCES: 1. Bertin, J. J. and Cummings, R. M. Critical hypersonic aerothermodynamic phenomena. Annu. Rev. Fluid Mech., 38(1), 2006, pp. 129-157. https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1007&context=aero_fac 2. Bertin, J. J. Hypersonic aerothermodynamics. AIAA, Washington, cop. 1994. https://search.worldcat.org/title/1022808140 3. Heiser, W. H. and Pratt, D. T. Hypersonic Airbreathing Propulsion. AIAA, Washington, D.C., 1994. https://search.worldcat.org/title/123496950 KEYWORDS: Hypersonic; Fluid-Thermal-Structural Interaction; Computational Aerothermodynamics; Multidisciplinary Physics-Based Modeling; Digital Engineering; Air-Breathing Hypersonic Vehicle