CAD-based shape optimisation with CFD using a discrete adjoint

SUMMARY One of the major challenges of shape optimisation in practical industrial cases is to generically parametrise the wide range of complex shapes. A novel approach is presented, which takes CAD descriptions as input and produces the optimal shape in CAD form using the control points of the Non‐...

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Bibliographic Details
Published in:International journal for numerical methods in fluids 2014-01, Vol.74 (3), p.153-168
Main Authors: Xu, Shenren, Jahn, Wolfram, Müller, Jens-Dominik
Format: Article
Language:English
Subjects:
Adjoints
CAD
Computational fluid dynamics
Computer aided design
Deformation
Descriptions
discrete adjoint
Mathematical analysis
Mathematical models
NURBS
Optimization
shape optimisation
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Summary:SUMMARY One of the major challenges of shape optimisation in practical industrial cases is to generically parametrise the wide range of complex shapes. A novel approach is presented, which takes CAD descriptions as input and produces the optimal shape in CAD form using the control points of the Non‐Uniform Rational B‐Splines (NURBS) boundary representation as design variables. An implementation of the NURBS equations in source allows to include the CAD‐based shape deformation inside the design loop and evaluate its sensitivities efficiently and robustly. In order to maintain or establish the required level of geometric continuity across patch interfaces, geometric constraints are imposed on the control point displacements. The paper discusses the discrete adjoint flow solver used and the computation of the complete sensitivities of the design loop by differentiating all components using automatic differentiation tools. The resulting rich but smooth deformation space is demonstrated on the optimisation of a vehicle climate duct. Copyright © 2013 John Wiley & Sons, Ltd. Gradient‐based shape‐optimisation is performed with the CAD description in the design loop by modifying the control points of the NURBS patches. The NURBS description guarantees a smooth shape, the algorithm maintains continuity between patch interfaces, which is essential for industrial application and generic CAD geometries. The figure shows initial and final shape and contours of velocity magnitude for an industrial air duct when minimising the pressure drop. The approach produces significant deformations, the streak‐like deformation suppresses separation and secondary flow.
ISSN:0271-2091
1097-0363
DOI:10.1002/fld.3844