On spectral linear stochastic estimation

Tinney, Charles E.; Coiffet, F.; Delville, J.; Hall, Andre; Jordan, Peter; Glauser, Mark

doi:10.1007/s00348-006-0199-5

Cited by 150 publications

(118 citation statements)

References 23 publications

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“…On the other hand, the frequency spectrum of the axial velocity fluctuations near the nozzle lip for a turbulent jet is known to be flat up to St D ≈ 0.5. 33,34 This observation is used to scale the PSE solutions for m = 0 such that their axial velocity components are unity at (x = 0.5D, r = 0.5D). The resulting pressure amplitudes for the different frequencies at the location of the near-field linear array are shown in Figure 6(b).…”

Section: B Comparison With Pse Analysismentioning

confidence: 99%

The impulse response of a high-speed jet forced with localized arc filament plasma actuators

et al. 2012

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Experimental study of planar opposed jets with acoustic excitation Phys. Fluids 25, 014108 (2013) Similarity analysis of the momentum field of a subsonic, plane air jet with varying jet-exit and local Reynolds numbers Phys. Fluids 25, 015115 (2013) Electrohydrodynamic printing under applied pole-type nozzle configuration Appl. Phys. Lett. 102, 024101 (2013) Effects of fluid properties and laser fluence on jet formation during laser direct writing of glycerol solution J. Appl. Phys. 112, 083105 (2012) We present experimental and theoretical analyses of the response of high-speed, highReynolds-number, round jets to impulsive forcing with arc-filament-plasma actuators. The impulse response is obtained with forcing Strouhal numbers, based on the nozzle exit diameter and exit center line velocity, less than 0.1. The resulting phase-averaged near-field pressure signature displays a compact wave with a positive peak preceding a negative one, indicative of a large scale structure in the shear layer of the jet. Scaling laws derived by operating the jet at four subsonic Mach numbers are used to distinguish this hydrodynamic component of the phase-averaged jet response from the direct actuator noise. As the forcing frequency increases, the compact waves in the near-field pressure signal overlap each other, indicating interaction of the growing seeded structures. For this regime, the phase-averaged response is approximately replicated by linear superposition of the impulse response, thereby demonstrating the quasi-linearity of structure interaction. A novel application of linear parabolized stability theory yields a successful model of the impulse response. C 2012 American Institute of Physics. [http://dx

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Section: B Comparison With Pse Analysismentioning

confidence: 99%

The impulse response of a high-speed jet forced with localized arc filament plasma actuators

et al. 2012

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“…Kernel H is equal to the inputoutput cross-spectrum, divided by the input spectrum, and may be expressed in terms of a gain, |H(z; f )|, and phase, φ(z; f ). Intuitively, the gain is the scaling factor for each Fourier mode during a linear stochastic estimate of the output [39][40][41], whereas the scale-dependent phase accounts …”

Section: (B) Conditional Structure and Inclinationmentioning

confidence: 99%

Reynolds number trend of hierarchies and scale interactions in turbulent boundary layers

Baars

Hutchins

Marušić

2017

Phil. Trans. R. Soc. A.

118

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Small-scale velocity fluctuations in turbulent boundary layers are often coupled with the larger-scale motions. Studying the nature and extent of this scale interaction allows for a statistically representative description of the small scales over a time scale of the larger, coherent scales. In this study, we consider temporal data from hot-wire anemometry at Reynolds numbers ranging from Re τ ≈2800 to 22 800, in order to reveal how the scale interaction varies with Reynolds number. Large-scale conditional views of the representative amplitude and frequency of the small-scale turbulence, relative to the large-scale features, complement the existing consensus on large-scale modulation of the small-scale dynamics in the near-wall region. Modulation is a type of scale interaction, where the amplitude of the small-scale fluctuations is continuously proportional to the near-wall footprint of the large-scale velocity fluctuations. Aside from this amplitude modulation phenomenon, we reveal the influence of the large-scale motions on the characteristic frequency of the small scales, known as frequency modulation. From the wall-normal trends in the conditional averages of the small-scale properties, it is revealed how the near-wall modulation transitions to an intermittent-type scale arrangement in the log-region. On average, the amplitude of the small-scale velocity fluctuations only deviates from its mean value in a confined temporal domain, the duration of which is fixed in terms of the local Taylor time scale. These concentrated temporal regions are centred on the internal shear layers of the large-scale uniform momentum zones, which exhibit regions of positive and negative streamwise velocity fluctuations. With an increasing scale separation at high Reynolds numbers, this interaction pattern encompasses the features found in studies on internal shear layers and concentrated vorticity fluctuations in high-Reynolds-number wall turbulence. This article is part of the themed issue ‘Toward the development of high-fidelity models of wall turbulence at large Reynolds number’.

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“…In contrast, [7], [17] proposed to take into account integrated temporal data by assuming a linear dependence between the modal coefficients and the flow measurements in a non-local way, by working in the frequency domain. Letα be the Fourier transform of α andf j that of f j , then for each frequency we poseα j = Ns k=1Γ kjfk (10) whereΓ kj is a matrix obtained by appropriate ensemble averages and depends on the frequency.…”

Section: Non-linear Observermentioning

confidence: 99%

A non-linear observer for unsteady three-dimensional flows

Buffoni

Camarri

Iollo

et al. 2008

Journal of Computational Physics

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A method is proposed to estimate the velocity field of an unsteady flow using a limited number of flow measurements. The method is based on a non-linear low-dimensional model of the flow and on expanding the velocity field in terms of empirical basis functions. The main idea is to impose that the coefficients of the modal expansion of the velocity field give the best approximation to the available measurements and that at the same time they satisfy as close as possible the nonlinear low-order model. The practical use may range from feedback flow control to monitoring of the flow in non-accessible regions. The proposed technique is applied to the flow around a confined square cylinder, both in two-and three-dimensional laminar flow regimes. Comparisons are provided with existing linear and non-linear estimation techniques.

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On spectral linear stochastic estimation

Cited by 150 publications

References 23 publications

The impulse response of a high-speed jet forced with localized arc filament plasma actuators

The impulse response of a high-speed jet forced with localized arc filament plasma actuators

Reynolds number trend of hierarchies and scale interactions in turbulent boundary layers

A non-linear observer for unsteady three-dimensional flows

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