Engine Modeling for Small-Disturbance-CFD Related to Aircraft Flutter Investigations

Impact of Airframe–Propulsion System Modeling Strategies on Key Structural Performance Metrics

“…Early design stage propulsion system structural modeling strategies for integrated airframe-propulsion system aeroelastic analysis are targeted toward acquiring global structural performance metrics, e.g., inertial loads, and generally employ Zero-and One-Dimensional (0D, 1D) structural idealizations [6][7][8]. The airframe is conventionally modeled using 1D beam elements located along the elastic axis [5,15] with concentrated masses along the leading and trailing edge -termed a reduced FEM -while a range of structural idealizations have been employed for the propulsion system.…”

“…Schulze et al [10] employ a comparatively detailed DLM model, idealizing power plant aerodynamic surfaces as a cylindrical body. Higher-fidelity Computational Fluid Dynamics (CFD) models have been employed with reduced airframe FEMs for flutter [8,15] and gust analysis [21] -Reimer et al [24] perform a comparison between both methods.…”

“…Eigenfrequencies corresponding to lower-order eigenmodes dominated by airframe deformations exhibit frequencies 10-15% lower than similar aircraft [5,8], occurring at comparable mode numbers. Lower-order airframe dominated eigenfrequencies are due to relatively higher airframe compliance, arising from dissimilar suites of sizing load cases and omission of displacement constraints in the sizing framework.…”

“…Nevertheless, similarity with equivalently idealized aircraft aeroelastic models [5,6] indicates aircraft level mass and stiffness distributions are modeled to an appropriate level of accuracy for early design stages to capture dynamic aeroelastic responses. Furthermore, power plant swing frequencies are 2 -2.5𝐻𝑧 [5,8,9]. Thus, the developed DLM-FD-SD FEM with GFEM propulsion system is sufficiently representative of propulsion system responses for conventional TAW aircraft with under-wing mounted, high bypass ratio, turbofan power plants.…”

“…Modeling and analysis strategies to facilitate architectural decisions during early design stages benefit from reducing their fidelity as much as possible. Integrated airframe-propulsion system aeroelastic analysis performed in literature [5][6][7][8][9][10][11] has employed a range of lower fidelity propulsion system structural modeling strategies, typically idealizing the power plant as a concentrated mass with various structural idealizations of the integrating structure, and associatively, the stiffness of the propulsion system as a whole. Whole Engine Models (WEMs) [12][13][14] represent high fidelity idealizations of the propulsion system and integrating structure, facilitating evaluation of a broader range of key structural metrics such as internal loads and natural frequencies of the various propulsion sub-systems, with a greater level of detail and accuracy.…”