Determination of loads on a flexible wing of a fighter jet via surrogate models

Zafer, Özgür
This study presents the load analysis of a flexible wing for a fighter jet. The main purpose is to demonstrate the application of a rapid methodology for aero-structural coupling and the determination of flexible wing loads suitable for the initial design stages of a fighter jet. The present methodology allows designers to include flexibility effects early on and to explore the design space quickly for flexible wing loads. The methodology uses an aerodynamic database obtained with high-fidelity computational fluid dynamics (CFD) and loads at unknown flight parameters are calculated with surrogate models. Surrogate models reduce the computational time by replacing computationally expensive CFD simulations with approximate functions which are much faster to evaluate. In order to acquire the loads on a flexible wing of the fighter jet, required models for aero-structural coupling, namely; aerodynamic, structural and surrogate models are developed. The aerodynamic model of the generic fighter aircraft is a three-dimensional wing-body configuration and aerodynamic analysis is conducted using Euler simulations in ANSYS Fluent. The results obtained from the aerodynamic analysis are validated with the available experimental results. On the other hand, the structural model is a two-dimensional beam stick model (BSM) to decrease the computational time. The BSM generated from a wing’s finite element model (FEM) and the modal properties of BSM are tuned to achieve similar modal characteristics as that of the FEM. To generate an aerodynamic database efficiently, surrogate models are also utilized and are then compared in terms of the generation of the aerodynamic database with minimal CFD simulations. According to this criterion, the surrogate model is selected for this particular research problem. The aeroelastic model is generated using the aerodynamic loads obtained from the optimized surrogate model and mode shapes from the BSM. Flexible wing loads are calculated from the present model and verified with Nastran FlighLoads (FLDS) module which uses low-fidelity, linear aerodynamic theory to calculate aerodynamic loads. Once the validation process is completed, the developed aeroelastic model takes the high-fidelity CFD solutions as input to determine the flexible wing loads and compares the final computed results with the FLDS. In conclusion, the proposed methodology produces satisfactory results compared to the CFD simulations, hence, it can be used in the early design phase to significantly reduce computational time and cost.


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Citation Formats
Ö. Zafer, “Determination of loads on a flexible wing of a fighter jet via surrogate models,” M.S. - Master of Science, Middle East Technical University, 2023.