09:40
Loads 1
Chair: Felix Arevalo
09:40
30 mins
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Differentiable Aeroelastic Framework Suitable for Industrial Modelling of Nonlinear Loads on Accelerators
Alvaro Cea, Rafael Palacios
Abstract: This paper presents a new simulation environment for time-domain nonlinear aeroelastic analysis built for performance and that is suitable for modern hardware architectures such as GPUs.
The numerical library JAX and a novel description of the aircraft dynamics are brought together into a highly vectorised codebase that achieves two orders of magnitude accelerations compare to conventional implementations. This brings full-vehicle simulations to run close to if not in real-time, thus opening new possibilities for aircraft design optimization and aeroelastic analysis.
The computational edge provided by GPUs is shown in a free-flying very flexible structure. It follows an extensive verification by comparison with MSC Nastran full-FE linear and nonlinear structural solutions on a representative aeroplane model.
Furthermore, the nonlinear gust response of an industrial configuration with over half a million degrees-of-freedom is computed, and it is faster than its frequency-based, linear equivalent as implemented by commercial packages. Therefore this could be harnessed by aircraft loads engineers to add geometrically nonlinear effects to their existing workflows at no extra computational effort. Finally, automatic differentiation on both static and dynamic responses is validated against finite-differences.
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10:10
30 mins
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Comparative analysis of flight maneuver loads between flexible and rigid aircraft
Eduardo de Melo Pinto, Flávio Cardoso-Ribeiro, Fernando de Oliveira Moreira
Abstract: The analysis of aircraft loads during flight maneuvers plays a pivotal role in ensuring structural integrity, safety and the design of lighter and more fuel-efficient structures. This study focuses on a comparative analysis of internal load diagrams for a flexible aircraft and its rigid-body counterpart, emphasizing the impact of structural flexibility on flight dynamics and loads. The research employs a dynamically-coupled formulation for the flexible model, considering small deformations and inertially coupled equations of motion. The aerodynamic loads are calculated with a quasi-steady VLM model, and the structural dynamics is represented by a linear FEM model. The rigid-body model is obtained by neglecting structural flexibility, setting the number of elastic modes to zero. To calculate the internal loads, the force summation method is employed.
Three maneuvers from CS-25 specifications are simulated: the symmetrical unchecked (or maximum pitch control displacement) and checked maneuvers, and the roll maneuver. For the unchecked maneuver, the flexible model exhibits a slightly slower response and reduced wing and horizontal tail loads compared to the rigid model, attributed to inertial, aerodynamic, and propulsive coupling. In the checked maneuver, the flexible model displays nuanced differences in loads, because the elevator profile is characterized by a sinusoidal input with a frequency matching the short period mode, which significantly differs from the frequency of the first elastic mode. The roll maneuver reveals a slower response and steady roll rate in the flexible model due to structural deformations and aileron control effectiveness, consequently the wing internal loads of flexible model is smaller. Detailed comparisons of pertinent parameters and wing and horizontal tail internal loads for all maneuvers highlight differences in aerodynamic, inertial, and propulsive contributions. Despite variations, the study emphasizes the importance of considering structural flexibility in analyzing flight maneuver loads and the need for more precise and efficient methods in load analysis to address the evolving landscape of aircraft design.
The framework developed may be employed to calculate any flight and ground condition loads if some upgrades are performed, e.g., the implementation of an unsteady aerodynamic model to calculate turbulence encounter loads, and control laws to design a load alleviation system.
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