Analysis of spatiotemporal inner-outer large-scale interactions in turbulent channel flow by multivariate empirical mode decomposition

Mäteling, Esther; Schröder, Wolfgang

doi:10.1103/physrevfluids.7.034603

Cited by 7 publications

(22 citation statements)

References 41 publications

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“…Motivated by such observations of coherent structures and their interactions, there has been intensive efforts in recent years to investigate the scale interactions in wall turbulence by quantifying turbulent energy transfers between different scales [6][7][8][9][10][11][12][13][14][15][16][17][18][19] . Interestingly, both forward (from larger to smaller scales) and inverse (from smaller to larger scales) turbulent energy cascades have been observed in these studies, and the relations of such interscale energy transfers to the dynamics of coherent structures, such as the self-sustaining cycles of each inner and outer structure 9,12,19,20 , the inner-outer interactions 9,10,[17][18][19][21][22][23] , merging/splitting of wall-attached hair-pin vortices 16 , etc. have been discussed.…”

Section: Introductionmentioning

confidence: 88%

Spectral analysis on dissimilarity between turbulent momentum and heat transfers in plane Couette turbulence

Kawata,

Tsukahara

2022

Preprint

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Nonlinear interaction between different scales in turbulence results in both interscale and spatial transport of turbulent energy, and the role of such scale interactions in turbulent heat transfer mechanism is also of practical importance from the engineering viewpoint. In the present study, we investigate a turbulent plane Couette flow with passive-scalar heat transfer at the Prandtl number 0.71, in order to address the similarity/difference between the scale interactions in the velocity and temperature fields. The constant-temperature-difference boundary condition is used so that the mean velocity and temperature profiles are similar, and then the roles of interscale and spatial transports are compared for the spectral transport budgets of the turbulent energies and temperature-related statistics. We show that turbulent heat transfer occurs at relatively small streamwise length scales compared to momentum transfer, although molecular diffusion is more significant in the temperature field as the Prandtl number is less than 1. Detailed analysis on the transport budgets of the temperature-related spectra shows that scale interactions in temperature field supply more energy to small scales than those in velocity field. Such significant temperature cascade leads to more energetic temperature fluctuation at small scales, which eventually results in the dissimilarity between the spectra of turbulent heat and momentum transfers.

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Section: Introductionmentioning

confidence: 88%

Spectral analysis on dissimilarity between turbulent momentum and heat transfers in plane Couette turbulence

Kawata,

Tsukahara

2022

Preprint

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“…The time-resolved spatial velocity fields are decomposed into scale-based modal representations by an extended version of the 2-D EMD (Mäteling & Schröder 2022). Unlike classical Fourier filtering, the EMD is able to process nonlinear and unsteady data, which are both essential characteristics of turbulent flows.…”

Section: Methodical Approachmentioning

confidence: 99%

“…In the present analysis, a 2-D NA-MEMD is applied to the velocity fields (Mäteling & Schröder 2022). In general, the multivariate data can be composed of different fluid-dynamical quantities such as velocity, pressure or density fields.…”

Section: Methodical Approachmentioning

confidence: 99%

“…The details of the 2-D NA-MEMD algorithm are outlined in Mäteling & Schröder (2022). In the following, only the necessary application-specific information is provided without repeating the algorithmic basics.…”

Section: Methodical Approachmentioning

confidence: 99%

“…2012). Recently, Mäteling & Schröder (2022) introduced an approach revealing the time-dependent properties of the spatial inner–outer interactions using a two-dimensional (2-D), noise-assisted multivariate empirical mode decomposition (NA-MEMD) to determine the involved large-scale structures. The 2-D NA-MEMD simultaneously decomposes spatial velocity fields of the inner and the outer layer into physically meaningful modes, which are sorted by the inherent scale size and are continuous in time.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

How spanwise travelling transversal surface waves change the near-wall flow

Mäteling

Albers²,

Schröder³

2023

J. Fluid Mech.

Self Cite

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The alteration of the near-wall flow field of a turbulent boundary layer flow subjected to spanwise travelling transversal surface waves at a friction Reynolds number $Re_\tau \approx 1525$ is investigated. The results of a spatial noise-assisted multivariate empirical mode decomposition reveal that this flow control method periodically induces near-wall large-scale bursts while simultaneously lowering the energetic content of small-scale features. The increasing occurrence of intense large-scale ejections in the near-wall region is of particular importance for reducing the wall-shear stress since these ejections balance large-scale sweeps originating from the outer layer. Thus, they corrupt the outer-layer impact on the near-wall dynamics and, consequently, the overall fluctuation intensity at the wall is attenuated. This disturbed top-down momentum exchange is highlighted by an inner–outer interaction analysis, which further reveals an increased bottom-up communication provoked by the large-scale ejections. Moreover, it is shown that the periodic secondary flow field induced by the actuation interferes with the quasi-streamwise vortices in the near-wall region. The velocity gradients of the secondary flow field deform the vortices’ cross-section into an elliptic shape, which yields an unstable vortex state resulting in vortex disintegration. In combination with the effect of the large-scale ejections, the reduced number of quasi-streamwise vortices compared with the undisturbed boundary layer flow results in a decreased wall-normal momentum exchange and the widening and weakening of near-wall streaks. This yields a reduced fluctuation intensity in the near-wall region that lowers the overall wall-shear stress level.

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Impact of Reynolds Number on the Drag Reduction Mechanism of Spanwise Travelling Surface Waves

Lagemann,

Albers,

Lagemann

et al. 2023

Flow Turbulence Combust

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Analysis of spatiotemporal inner-outer large-scale interactions in turbulent channel flow by multivariate empirical mode decomposition

Cited by 7 publications

References 41 publications

Spectral analysis on dissimilarity between turbulent momentum and heat transfers in plane Couette turbulence

Spectral analysis on dissimilarity between turbulent momentum and heat transfers in plane Couette turbulence

How spanwise travelling transversal surface waves change the near-wall flow

Impact of Reynolds Number on the Drag Reduction Mechanism of Spanwise Travelling Surface Waves

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