A parametric and feasibility study for data sampling of the dynamic mode decomposition: range, resolution, and universal convergence states

Cruz Y. Li, Zengshun Chen, Tim K.T. Tse, Asiri U. Weerasuriya, Xuelin Zhang, Yunfei Fu, Xisheng Lin

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)

Abstract

Scientific research and engineering practice often require the modeling and decomposition of nonlinear systems. The dynamic mode decomposition (DMD) is a novel Koopman-based technique that effectively dissects high-dimensional nonlinear systems into periodically distinct constituents on reduced-order subspaces. As a novel mathematical hatchling, the DMD bears vast potentials yet an equal degree of unknown. This effort investigates the nuances of DMD sampling with an engineering-oriented emphasis. It aimed at elucidating how sampling range and resolution affect the convergence of DMD modes. We employed the most classical nonlinear system in fluid mechanics as the test subject—the turbulent free-shear flow over a prism—for optimal pertinency. We numerically simulated the flow by the dynamic-stress Large-Eddies Simulation with Near-Wall Resolution. With the large-quantity, high-fidelity data, we parametrized and identified four global convergence states: Initialization, Transition, Stabilization, and Divergence with increasing sampling range. Results showed that Stabilization is the optimal state for modal convergence, in which DMD output becomes independent of the sampling range. The Initialization state also yields sufficient accuracy for most system reconstruction tasks. Moreover, defying popular beliefs, over-sampling causes algorithmic instability: as the temporal dimension, n, approaches and transcends the spatial dimension, m (i.e., m < n), the output diverges and becomes meaningless. Additionally, the convergence of the sampling resolution depends on the mode-specific dynamics, such that the resolution of 15 frames per cycle for target activities is suggested for most engineering implementations. Finally, a bi-parametric study revealed that the convergence of the sampling range and resolution are mutually independent.

Original languageEnglish
Pages (from-to)3683-3707
Number of pages25
JournalNonlinear Dynamics
Volume107
Issue number4
DOIs
Publication statusPublished - Mar 2022
Externally publishedYes

Keywords

  • Dynamic mode decomposition
  • Large-eddies simulation
  • Reduced-order model
  • Sampling convergence
  • Sampling resolution
  • Turbulent free-shear flow

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