NAFEMS Americas and Digital Engineering (DE) teamed up (once again) to present CAASE, the (now Virtual) Conference on Advancing Analysis & Simulation in Engineering, on June 16-18, 2020!

CAASE20 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, unlike any other, to share experiences, discuss relevant trends, discover common themes, and explore future issues, including:
-What is the future for engineering analysis and simulation?
-Where will it lead us in the next decade?
-How can designers and engineers realize its full potential?
What are the business, technological, and human enablers that will take past successful developments to new levels in the next ten years?

Resource Abstract

Modern design processes for structural systems across a variety of industries are becoming ever more reliant on computational models and simulations. Next generation aerospace structures are subject complex multidisciplinary loading including aeroelasticity and fluid-structure interaction, conjugate heat transfer and thermoelasticity, and structural-acoustics. In addition, it is not uncommon for these combined loads to drive responses into the nonlinear regime. Due to the inherent complexity of the governing physics, the dependency between design responses and design parameters is non-intuitive, making the use of traditional design processes difficult in these cases. As a result, a simulation-driven design process can not only reduce design cycle time, but often yield improved performance as well.

Commercial finite element analysis tools are capable of accurately modeling nonlinear and tightly coupled multidisciplinary responses. However, these tools have yet to rigorously incorporate analytical sensitivity analysis methods that provide gradients between design responses and design variables for coupled systems, such as CFD-based aerodynamics and nonlinear FEA-based structures. This feature is a critical component for enabling efficient use of design optimization methods in simulation-driven design. While methods have been proposed to address these issues, such as the use of surrogate models to approximate responses, obtaining an accurate surrogate for a system with a large number of design parameters can lead to prohibitive computational costs. Traditional finite difference methods prove too computationally expensive as well for a high number of design parameters. Alternatively, the equivalent static load method has been adapted to approximate sensitivities of nonlinear responses using cheaper linear analyses; however, these methods perform poorly when the loading is highly design dependent, which is common in many aerospace structures.

This work presents the Multidisciplinary-design Adaptation and Sensitivity Toolkit (MAST), which addresses the need for efficient FEA-based analytical sensitivity analysis for multiphysics, optimization-driven design. MAST is an open-source, object-oriented, C++ finite element analysis framework that is jointly developed by Mississippi State University (MSU) and the Air Force Research Laboratory (AFRL). Development has focused on efficiently and reliably quantifying static and dynamic stability characteristics of nonlinear multidisciplinary systems and providing analytical sensitivity analysis to enable gradient-based design. MAST utilizes multiple open-source libraries to achieved high performance in both the assembly and solution of finite element systems on both local and distributed architectures. Both the direct and adjoint methods of sensitivity analysis are implemented to allow for efficient sensitivity analysis in either designs with a large number of parameters such as topology optimization or with a large number of constraints. MAST also interfaces to multiple optimizers to allow the design to be automatically driven towards an optimum.

This work will present a discussion and demonstration of the capabilities of MAST. A built-up generic supersonic aircraft wing structure with control surfaces is modeled using industry-level modeling representations. The nonlinear static, modal, and aeroelastic maneuver responses of the wing will be analyzed using MAST. The analytical sensitivity of these responses with respect to changes in skin panel and spar/rib thicknesses are also calculated. The accuracy of the responses and sensitivities are numerically verified against commercial software and finite differences, respectively. The use of efficient sensitivities to size the thickness variables against constraints from multiple loading conditions will also be demonstrated in an optimization-based, simulation-driven design process.

Distribution A. Approved for public release: distribution unlimited. (88ABW-2019-5868)