A Hybrid Method for Dynamic Thermal Simulation in Aircraft Compartments From Ground Operations to Supersonic Flight

Predicting the temperature distribution across different areas of an aircraft under steady-state and transient conditions is crucial, particularly in the preliminary design phase. Whereas tests and CFD offer solutions, they are costly, impractical for varying scenarios, and time-consuming, unlike 1D system simulations. However, most 1D simulation studies in the literature rely solely on the Lumped Method (LM), which is inadequate for regions like the fuselage or dome, which consists of composite structures designed to insulate the aircraft's interior from harsh external environments. In the present study, a hybrid 1D system simulation method is developed that, depending on the thermal behavior characteristics of each area, combines the LM with the Finite Difference Method (FDM) and uses them separately in a single simulation to model different areas inside an aircraft. This approach enhances the accuracy of the results while maintaining runtime efficiency. The method is also tailored for low supersonic (1 < M < 3) flight, where the importance of the method is particularly highlighted since the spatial temperature variation across the thickness of the structure is desired to ensure that the interior temperature does not exceed allowable limits. In high-speed flows, the method incorporates the Eckert reference temperature method to calculate the heat transfer coefficient, accounting for compressibility effects. Furthermore, a numerical modification to the FDM is introduced to relax stability criteria as a part of this study, an adjustment particularly significant in high heat flux scenarios encountered during high-speed flight. The study is compared with five different AMESim 1D system simulations and a test data, showing good agreement with both.