Wavelet analysis of unsteady flows: Application on the determination of the Strouhal number of the transient wake behind a single cylinder

Indrusiak, Maria Luiza Sperb; Möller, Sérgio Viçosa

doi:10.1016/j.expthermflusci.2010.10.001

Cited by 29 publications

(8 citation statements)

References 28 publications

(34 reference statements)

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“…The specific type of wavelet filter plays a lesser role for MODWPT, especially when a large filter is used, as shown in § A.4. Among the most commonly used wavelet filters, this work has chosen the Daubechies wavelets as they have been widely adopted in turbulent flow applications (Indrusiak & Möller 2011;Rinoshika & Omori 2011;Mancinelli et al 2017). Detailed performance comparisons of different wavelets are included in § A.4.…”

Section: Selection Criteria For Wavelet Filter J and Nmentioning

confidence: 99%

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Time–frequency localisation of intermittent dynamics in a bistable turbulent swirl flame

Yin

Stöhr

2019

J. Fluid Mech.

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Section: Selection Criteria For Wavelet Filter J and Nmentioning

confidence: 99%

“…Non-periodic and unsteady dynamics often rejected by Fourier analysis is preserved in MRA. Besides direct implementation of MRA on data series acquired in turbulent flows (Ruppert-Felsot, Farge & Petitjeans 2009; Indrusiak & Möller 2011; Rinoshika & Omori 2011; Mancinelli et al. 2017; Kim et al.…”

Section: Introductionmentioning

confidence: 99%

Time–frequency localisation of intermittent dynamics in a bistable turbulent swirl flame

Yin

Stöhr

2019

J. Fluid Mech.

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“…Uncertainty analysis is based on value of the primary uncertainties in the experiment and the uncertainty of a certain variable, as presented by Moffat [27]. The uncertainty in the evaluation of the velocity depends Hot wires were used widely in the study of wake flows, e.g., Ong and Wallace [33], cited above, Nornberg and Sundem [30], Alam et al [1], Indrusiak and Möller [16], de Paula et al [12].…”

Section: Experimental Methodologymentioning

confidence: 99%

Characteristics of the wake formation and force distribution of the bistable flow on two cylinders side-by-side

Neumeister

Petry

Möller

2018

J Braz. Soc. Mech. Sci. Eng.

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This numerical study with experimental support examines the bistable phenomenon along two parallel smooth cylinders submitted to a uniform turbulent cross-flow. The spacing ratio P/D of the cylinders is 1.26, being D the cylinder diameter and P the distance between centers. The computational domain and the experimental tests section are equivalents. The Reynolds number based on the free mean velocity and cylinder diameter was Re = 2.2 × 10 4. For the numerical analysis, the Navier-Stokes equations were solved using finite volumes method for a URANS simulation (unsteady Reynolds averaged Navier-Stokes) with the kω-SST-SAS (shear stress tensor-scale adaptive simulation) turbulence model. Measurements were performed by means of hot wire anemometry technique, firstly to determine actual boundary conditions of flow velocity and turbulence intensity at the test section entrance, secondly to obtain velocity and velocity fluctuation at the wake of the cylinders in different positions along the cylinder height to corroborate the numerical results. By means of the numerical results of velocity, the process of the wake formation is described, showing that the bistability does not occur simultaneously along the cylinder, corroborated by a delay on the switching process of the simultaneously measured velocities and the cross-correlation function. This effect appears also in the results of cylinder wall pressure distribution as well as in lift and drag coefficients. Keywords Turbulent flow • Bistability • Two cylinders side-by-side • URANS simulation • Hot wires List of symbols A Area (m 2) C D Drag coefficient C L Lift coefficient C ′ D Drag coefficient fluctuation C ′ L Lift coefficient fluctuation D Cylinder diameter (m) GCI Grid convergence index ρ Density (kg/m 3) p Mean pressure (Pa) P Distance between cylinders (pitch) (m) P/D Pitch-to-diameter ratio Re Reynolds number, Re D = VD St Strouhal number, St = fD V t Time (s) x Axis direction x y Axis direction y z Axis direction z

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“…(4). According to [24,25], the DWT decomposes the energy of the time series in the respective scales and the summation of Eq. (4) can be considered as a portion of energy due the fluctuations in 2 j−1 scale.…”

Section: Fundamentals: Fourier and Wavelet Analysesmentioning

confidence: 99%

Wake behavior analysis for two circular cylinders placed at several angles to the flow

Habowski

Paula

Möller

2020

J Braz. Soc. Mech. Sci. Eng.

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This paper presents an experimental study performed in an aerodynamic channel using hot-wire anemometers and flow visualization by injection of dye in water in a hydraulic channel of the flow on two rigid cylinders placed at several angular positions to the flow, from 0° (side-by-side) to 90° (tandem). The main objective is to analyze the effects of the angular positions on the wake flow and the occurrence of bistability. Signal analysis was performed by means of Fourier and discrete and continuous wavelets transform. Time series of the angle of the flow emanating from the cylinder gap related to the main flow direction were obtained from flow visualization analysis to track the flow mode change in the water flow. Results from the aerodynamic channel showed the presence of bistability only for side-by-side configuration, and some attempts to modify the flow mode for 2.5° and 5° while through the flow visualization the flow mode changes were present for side-by-side and for 2.5° configurations. For the other angles investigated, the presence of a narrow and a wide wake without flow mode changes was observed. The difference between the results for 2.5° suggests that the scales and inertia involved in bistability phenomenon may affect the phenomenon. For 75°, the wide wake is so vigorous that it overwhelmed the narrow wake, displacing it downwards, and increasing the amplitude of the vertical component of the wake compared to smaller angles. The phenomena analyzed can be seen as two-dimensional for all cases, but the presence of vertical components shows that the resulting flow is three-dimensional. Keywords Bistable flow • Flow visualization • Hot wires • Turbulent flow • Wavelets List of symbols a,b Wavelet parameters B e Bandwidth (Hz) CWT Constant wavelet transform (-) d Cylinder diameter (mm) Db20 Daubechies wavelet

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Wavelet analysis of unsteady flows: Application on the determination of the Strouhal number of the transient wake behind a single cylinder

Cited by 29 publications

References 28 publications

Time–frequency localisation of intermittent dynamics in a bistable turbulent swirl flame

Time–frequency localisation of intermittent dynamics in a bistable turbulent swirl flame

Characteristics of the wake formation and force distribution of the bistable flow on two cylinders side-by-side

Wake behavior analysis for two circular cylinders placed at several angles to the flow

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