Schlegel, Michael and Noack, Bernd R. and Jordan, Peter and Dillmann, Andreas and Gröschel, Elmar and Schröder, Wolfgang and Wei, Mingjun and Freund, Jonathan B. and Lehmann, Oliver and Tadmor, Gilead (2012) On least-order flow representations for aerodynamics and aeroacoustics. Journal of Fluid Mechanics, Vol. 697, pp. 367-398. Cambridge University Press. DOI: 10.1017/jfm.2012.70.
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We propose a generalization of proper orthogonal decomposition (POD) for optimal flow resolution of linearly related observables. This Galerkin expansion, termed ‘observable inferred decomposition’ (OID), addresses a need in aerodynamic and aeroacoustic applications by identifying the modes contributing most to these observables. Thus, OID constitutes a building block for physical understanding, leastbiased conditional sampling, state estimation and control design. From a continuum of OID versions, two variants are tailored for purposes of observer and control design, respectively. Firstly, the most probable flow state consistent with the observable is constructed by a ‘least-residual’ variant. This version constitutes a simple, easily generalizable reconstruction of the most probable hydrodynamic state to preprocess efficient observer design. Secondly, the ‘least-energetic’ variant identifies modes with the largest gain for the observable. This version is a building block for Lyapunov control design. The efficient dimension reduction of OID as compared to POD is demonstrated for several shear flows. In particular, three aerodynamic and aeroacoustic goal functionals are studied: (i) lift and drag fluctuation of a two-dimensional cylinder wake flow; (ii) aeroacoustic density fluctuations measured by a sensor array and emitted from a two-dimensional compressible mixing layer; and (iii) aeroacoustic pressure monitored by a sensor array and emitted from a three-dimensional compressible jet. The most ‘drag-related’, ‘lift-related’ and ‘loud’ structures are distilled and interpreted in terms of known physical processes.
|Additional Information:||published online 16 March 2012|
|Title:||On least-order flow representations for aerodynamics and aeroacoustics|
|Journal or Publication Title:||Journal of Fluid Mechanics|
|In Open Access:||No|
|In ISI Web of Science:||Yes|
|Page Range:||pp. 367-398|
|Publisher:||Cambridge University Press|
|Keywords:||aeroacoustics, low-dimensional models, wakes/jets|
|HGF - Research field:||Aeronautics, Space and Transport|
|HGF - Program:||Aeronautics|
|HGF - Program Themes:||Aircraft Research|
|DLR - Research area:||Aeronautics|
|DLR - Program:||L AR - Aircraft Research|
|DLR - Research theme (Project):||L - Flight Physics|
|Institutes and Institutions:||Institute of Aerodynamics and Flow Technology > Leitungsbereich AS GO|
|Deposited By:||Ilka Micknaus|
|Deposited On:||20 Apr 2012 13:24|
|Last Modified:||26 Mar 2013 13:38|
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