Searching turbulence for periodic orbits with dynamic mode decomposition
| Autor: | Jacob Page, Rich R. Kerswell |
|---|---|
| Přispěvatelé: | Kerswell, Richard [0000-0001-5460-5337], Apollo - University of Cambridge Repository |
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Series (mathematics)
Computer science Mechanical Engineering Computation Fluid Dynamics (physics.flu-dyn) FOS: Physical sciences low-dimensional models Physics - Fluid Dynamics Solver Condensed Matter Physics 01 natural sciences 010305 fluids & plasmas computational methods Flow (mathematics) Mechanics of Materials 0103 physical sciences Trajectory Dynamic mode decomposition Vector field 010306 general physics Algorithm Eigenvalues and eigenvectors |
| Zdroj: | Page, J & Kerswell, R R 2020, ' Searching turbulence for periodic orbits with dynamic mode decomposition ', Journal of Fluid Mechanics, vol. 886, A28 . https://doi.org/10.1017/jfm.2019.1074 |
| DOI: | 10.1017/jfm.2019.1074 |
| Popis: | We present a new method for generating robust guesses for unstable periodic orbits (UPOs) by post-processing turbulent data using dynamic mode decomposition (DMD). The approach relies on the identification of near-neutral, repeated harmonics in the DMD eigenvalue spectrum from which both an estimate for the period of a nearby UPO and a guess for the velocity field can be constructed. In this way, the signature of a UPO can be identified in a short time series without the need for a near recurrence to occur, which is a considerable drawback to recurrent flow analysis, the current state of the art. We first demonstrate the method by applying it to a known (simple) UPO and find that the period can be reliably extracted even for time windows of length one quarter of the full period. We then turn to a long turbulent trajectory, sliding an observation window through the time series and performing many DMD computations. Our approach yields many more converged periodic orbits (including multiple new solutions) than a standard recurrent flow analysis of the same data. Furthermore, it also yields converged UPOs at points where the recurrent flow analysis flagged a near recurrence but the Newton solver did not converge, suggesting that the new approach can be used alongside the old to generate improved initial guesses. Finally, we discuss some heuristics on what constitutes a ‘good’ time window for the DMD to identify a UPO. |
| Databáze: | OpenAIRE |
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