Presented By: Aerospace Engineering
AE Defense: Component-Based Aerodynamic Shape Optimization Using Overset Meshes
Aerospace Engineering PhD Candidate: Ney Rafael Secco, Dissertation Chair: Professor Joaquim R. R. A. Martins
Component-Based Aerodynamic Shape Optimization Using Overset Meshes
Ney Rafael Secco, Aerospace Engineering Ph.D. Candidate
Professor Joaquim R. R. A. Martins, Dissertation Chair
Advances in computational power allow the increase in the fidelity level of analysis tools used in conceptual aircraft design and optimization. These tools not only give more accurate assessments of aircraft efficiency but also provide insights to improve the performance of next-generation aircraft. Aerodynamic shape optimization involves the inclusion of aerodynamic analysis tools in optimization frameworks to maximize the aerodynamic efficiency of an aircraft configuration via modifications of its outer mold line.
When using CFD-based aerodynamic shape optimization, generating high-quality structured meshes for complex aircraft configurations becomes challenging, especially near junctions. Furthermore, mesh deformation procedures frequently generate negative volume cells when applied to these structured meshes during optimization. Complex geometries can be accurately modeled using overset meshes, whereby multiple high-quality structured meshes corresponding to different aircraft components overlap to model the complete aircraft configuration. However, from the standpoint of geometry manipulation, most methods operate on the entire geometry rather than on separate components, which diminishes the advantages of overset meshes.
To address this issue, we introduce a geometry module that operates on individual components and automatically computes their intersections to update overset meshes during optimization. We apply reverse-mode automatic differentiation to compute partial derivatives across this geometry module, so that it fits into an optimization framework that uses a hybrid adjoint method (ADjoint) to efficiently compute gradients for a large number of design variables.
By using these automatically updated meshes and the corresponding derivatives, we optimize the aerodynamic shape of the DLR-F6 geometry while allowing changes in the wing-fuselage intersection. Sixteen design variables control the fuselage shape and 128 design variables determine the wing surface. Under transonic flight conditions, the optimization reduces drag by 16 counts (5\%) compared with the baseline design.
We also use this approach to minimize drag of the PADRI 2017 strut-braced wing benchmark for a fixed lift constraint at transonic flight conditions. The drag of the optimized configuration is 15\% lower than the baseline due to the reduction of shocks and separation in the wing-strut junction region. This result is an example where high-fidelity modeling is required to quantify the benefits of a new aircraft configuration and address potential issues during the conceptual design.
The methodologies developed in this work give additional flexibility for geometry and mesh manipulation tools used in aerodynamic shape optimization frameworks. This extends the applicability of design optimization tools to provide insights to more complex cases involving multiple components, including unconventional aircraft configurations.
Dissertation Committee:
Chair: Professor Joaquim R. R. A. Martins
Cognate Member: Assistant Professor Jesse S. Capecelatro, Mechanical Engineering
Members: Professor Carlos E. S. Cesnik and Associate Professor Karthik Duraisamy
Publications
Journal Papers
Secco N. R., Jasa J. P., Kenway G. K. W., Martins J. R. R. A. Component-based Geometry Manipulation for Aerodynamic Shape Optimization with Overset Meshes. AIAA Journal. 2018. (Accepted).
Secco N. R., Martins J. R. R. A. RANS-based Aerodynamic Shape Optimization of a Strut-braced Wing with Overset Meshes. Journal of Aircraft. 2018. (Accepted).
Conference Papers
Secco N. R., Jasa J. P., Kenway G. K. W., Martins J. R. R. A. Component-based Geometry Manipulation for Aerodynamic Shape Optimization with Overset Meshes. 18th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference. Denver, CO. 2017.
Secco N. R., Martins J. R. R. A. RANS-based Aerodynamic Shape Optimization of a Strut-braced Wing with Overset Meshes. 2018 AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. Kissimmee, FL. 2018.
Ney Rafael Secco, Aerospace Engineering Ph.D. Candidate
Professor Joaquim R. R. A. Martins, Dissertation Chair
Advances in computational power allow the increase in the fidelity level of analysis tools used in conceptual aircraft design and optimization. These tools not only give more accurate assessments of aircraft efficiency but also provide insights to improve the performance of next-generation aircraft. Aerodynamic shape optimization involves the inclusion of aerodynamic analysis tools in optimization frameworks to maximize the aerodynamic efficiency of an aircraft configuration via modifications of its outer mold line.
When using CFD-based aerodynamic shape optimization, generating high-quality structured meshes for complex aircraft configurations becomes challenging, especially near junctions. Furthermore, mesh deformation procedures frequently generate negative volume cells when applied to these structured meshes during optimization. Complex geometries can be accurately modeled using overset meshes, whereby multiple high-quality structured meshes corresponding to different aircraft components overlap to model the complete aircraft configuration. However, from the standpoint of geometry manipulation, most methods operate on the entire geometry rather than on separate components, which diminishes the advantages of overset meshes.
To address this issue, we introduce a geometry module that operates on individual components and automatically computes their intersections to update overset meshes during optimization. We apply reverse-mode automatic differentiation to compute partial derivatives across this geometry module, so that it fits into an optimization framework that uses a hybrid adjoint method (ADjoint) to efficiently compute gradients for a large number of design variables.
By using these automatically updated meshes and the corresponding derivatives, we optimize the aerodynamic shape of the DLR-F6 geometry while allowing changes in the wing-fuselage intersection. Sixteen design variables control the fuselage shape and 128 design variables determine the wing surface. Under transonic flight conditions, the optimization reduces drag by 16 counts (5\%) compared with the baseline design.
We also use this approach to minimize drag of the PADRI 2017 strut-braced wing benchmark for a fixed lift constraint at transonic flight conditions. The drag of the optimized configuration is 15\% lower than the baseline due to the reduction of shocks and separation in the wing-strut junction region. This result is an example where high-fidelity modeling is required to quantify the benefits of a new aircraft configuration and address potential issues during the conceptual design.
The methodologies developed in this work give additional flexibility for geometry and mesh manipulation tools used in aerodynamic shape optimization frameworks. This extends the applicability of design optimization tools to provide insights to more complex cases involving multiple components, including unconventional aircraft configurations.
Dissertation Committee:
Chair: Professor Joaquim R. R. A. Martins
Cognate Member: Assistant Professor Jesse S. Capecelatro, Mechanical Engineering
Members: Professor Carlos E. S. Cesnik and Associate Professor Karthik Duraisamy
Publications
Journal Papers
Secco N. R., Jasa J. P., Kenway G. K. W., Martins J. R. R. A. Component-based Geometry Manipulation for Aerodynamic Shape Optimization with Overset Meshes. AIAA Journal. 2018. (Accepted).
Secco N. R., Martins J. R. R. A. RANS-based Aerodynamic Shape Optimization of a Strut-braced Wing with Overset Meshes. Journal of Aircraft. 2018. (Accepted).
Conference Papers
Secco N. R., Jasa J. P., Kenway G. K. W., Martins J. R. R. A. Component-based Geometry Manipulation for Aerodynamic Shape Optimization with Overset Meshes. 18th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference. Denver, CO. 2017.
Secco N. R., Martins J. R. R. A. RANS-based Aerodynamic Shape Optimization of a Strut-braced Wing with Overset Meshes. 2018 AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. Kissimmee, FL. 2018.
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