A primary spectral submanifold (SSM) is the unique smoothest nonlinear continuation of a nonresonant spectral subspace of a dynamical system linearized at a fixed point. Passing from the full nonlinear dynamics to the flow on an attracting primary SSM provides a mathematically precise reduction of the full system dynamics to a very low-dimensional, smooth model in polynomial form. A limitation of this model reduction approach has been, however, that the spectral subspace yielding the SSM must be spanned by eigenvectors of the same stability type. A further limitation has been that in some problems, the nonlinear behavior of interest may be far away from the smoothest nonlinear continuation of the invariant subspace . Here, we remove both of these limitations by constructing a significantly extended class of SSMs that also contains invariant manifolds with mixed internal stability types and of lower smoothness class arising from fractional powers in their parametrization. We show on examples how fractional and mixed-mode SSMs extend the power of data-driven SSM reduction to transitions in shear flows, dynamic buckling of beams, and periodically forced nonlinear oscillatory systems. More generally, our results reveal the general function library that should be used beyond integer-powered polynomials in fitting nonlinear reduced-order models to data.
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June 2023
Research Article|
June 12 2023
Nonlinear model reduction to fractional and mixed-mode spectral submanifolds
Special Collection:
Nonlinear Model Reduction From Equations and Data
George Haller
;
George Haller
a)
(Conceptualization, Formal analysis, Methodology, Supervision, Writing – original draft)
Institute for Mechanical Systems, ETH Zürich
, Leonhardstrasse 21, 8092 Zürich, Switzerland
a)Author to whom correspondence should be addressed: georgehaller@ethz.ch
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Bálint Kaszás
;
Bálint Kaszás
(Conceptualization, Data curation, Formal analysis, Writing – original draft, Writing – review & editing)
Institute for Mechanical Systems, ETH Zürich
, Leonhardstrasse 21, 8092 Zürich, Switzerland
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Aihui Liu
;
Aihui Liu
(Conceptualization, Data curation, Formal analysis, Writing – original draft)
Institute for Mechanical Systems, ETH Zürich
, Leonhardstrasse 21, 8092 Zürich, Switzerland
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Joar Axås
Joar Axås
(Conceptualization, Supervision, Writing – review & editing)
Institute for Mechanical Systems, ETH Zürich
, Leonhardstrasse 21, 8092 Zürich, Switzerland
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a)Author to whom correspondence should be addressed: georgehaller@ethz.ch
Chaos 33, 063138 (2023)
Article history
Received:
January 27 2023
Accepted:
May 18 2023
Citation
George Haller, Bálint Kaszás, Aihui Liu, Joar Axås; Nonlinear model reduction to fractional and mixed-mode spectral submanifolds. Chaos 1 June 2023; 33 (6): 063138. https://doi.org/10.1063/5.0143936
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