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Dynamic mode decomposition of cavitating flow around ALE 15 hydrofoil

Liu, Ming, Tan, Lei, Cao, Shuliang
Renewable energy 2019 v.139 pp. 214-227
energy, mathematical models, renewable energy sources
The Dynamic Mode Decomposition (DMD) and Proper Orthogonal Decomposition (POD) are employed to analyze the coherent structure of cavitating flow around ALE 15 hydrofoil. The snapshot data sequence is obtained from the numerical simulations by means of LES approach and modified Schnerr-Sauer cavitation model. Under cavitation number σ = 2.3, the cavitating flow around ALE 15 hydrofoil sheds at the short side while it almost remains stable at the long side. The eigenvalue distribution of DMD is symmetrical along the real axis of the plane, and the eigenvalues appear as conjugate pairs. The DMD method can accurately extract the frequency characteristics, and results show that the decomposed Mode at St = 2.224 is related to the shedding frequency of cloud cavitation, which agrees well with the shedding frequency of 2.208–2.805 in experimental measurement. The POD method can effectively analyze the major structure of high energy, in which the first four modes contain over 60% total energy of flow field. In comparison of POD, the DMD is more effective to decompose the complex flow field into uncoupled coherent structures with specific dynamic modes and corresponding frequencies.