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Open AccessArticle

Breaking the Kolmogorov Barrier in Model Reduction of Fluid Flows

School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078, USA
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Fluids 2020, 5(1), 26; https://doi.org/10.3390/fluids5010026
Received: 15 January 2020 / Revised: 13 February 2020 / Accepted: 14 February 2020 / Published: 18 February 2020
(This article belongs to the Special Issue Recent Numerical Advances in Fluid Mechanics)
Turbulence modeling has been always a challenge, given the degree of underlying spatial and temporal complexity. In this paper, we propose the use of a partitioned reduced order modeling (ROM) approach for efficient and effective approximation of turbulent flows. A piecewise linear subspace is tailored to capture the fine flow details in addition to the larger scales. We test the partitioned ROM for a decaying two-dimensional (2D) turbulent flow, known as 2D Kraichnan turbulence. The flow is initiated using an array of random vortices, corresponding to an arbitrary energy spectrum. We show that partitioning produces more accurate and stable results than standard ROM based on a global application of modal decomposition techniques. We also demonstrate the predictive capability of partitioned ROM through an energy spectrum analysis, where the recovered energy spectrum significantly converges to the full order model’s statistics with increased partitioning. Although the proposed approach incurs increased memory requirements to store the local basis functions for each partition, we emphasize that it permits the construction of more compact ROMs (i.e., of smaller dimension) with comparable accuracy, which in turn significantly reduces the online computational burden. Therefore, we consider that partitioning acts as a converter which reduces the cost of online deployment at the expense of offline and memory costs. Finally, we investigate the application of closure modeling to account for the effects of modal truncation on ROM dynamics. We illustrate that closure techniques can help to stabilize the results in the inertial range, but over-stabilization might take place in the dissipative range. View Full-Text
Keywords: reduced order modeling; Kolmogorov n-width; Galerkin projection; proper orthogonal decomposition; turbulent flows reduced order modeling; Kolmogorov n-width; Galerkin projection; proper orthogonal decomposition; turbulent flows
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MDPI and ACS Style

Ahmed, S.E.; San, O. Breaking the Kolmogorov Barrier in Model Reduction of Fluid Flows. Fluids 2020, 5, 26. https://doi.org/10.3390/fluids5010026

AMA Style

Ahmed SE, San O. Breaking the Kolmogorov Barrier in Model Reduction of Fluid Flows. Fluids. 2020; 5(1):26. https://doi.org/10.3390/fluids5010026

Chicago/Turabian Style

Ahmed, Shady E.; San, Omer. 2020. "Breaking the Kolmogorov Barrier in Model Reduction of Fluid Flows" Fluids 5, no. 1: 26. https://doi.org/10.3390/fluids5010026

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