Turbulence structures over irregular rough surfaces

Risultato della ricerca: Article

34 Citazioni (Scopus)

Abstract

Turbulent flow in a channel with irregular two-dimensional rough surfaces is analysed through wall-resolving large eddy simulation (LES). Both walls of the channel are roughened through the superimposition of sinusoidal functions having random amplitude and four different wavelengths. The downward shift of the velocity profile in the log region due to the roughness, known as roughness function, is well captured in the simulations. The spanwise and wall-normal turbulence intensities are found to increase with the roughness height, while the streamwise component decreases. The analysis of the Reynolds stress anisotropy tensor highlights a tendency towards isotropisation, confirmed by the vorticity rms. The analysis of the statistics shows that the effects of the roughness on the turbulent flow are greatly related to the increase of the height of the maximum peaks of the corrugations. Although the inner layer is dramatically affected by the wall irregularities, the outer layer appears not affected by the specific wall shape and a collapse of the turbulence statistics in smooth- and rough-wall conditions is observed. Much of the present results are consistent with the observations made over regular roughness, nevertheless the turbulence structures and the turbulent kinetic energy production analysis shows that the turbulence dynamics are directly affected by the local shape of the irregularities. The spatial inhomogeneities of the height of the roughness peaks and of the cavity region locally modifies the structures introducing variable length-scales. Overall the irregular roughness destroys the coherent pattern of the flow selectively, depending on the spatial distribution of the higher roughness peaks.
Lingua originaleEnglish
pagine (da-a)1-32
Numero di pagine32
RivistaJournal of Turbulence
Volume11
Stato di pubblicazionePublished - 2010

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Turbulence
roughness
Surface roughness
turbulence
irregularities
turbulent flow
Turbulent flow
Statistics
statistics
Reynolds stress
Large eddy simulation
large eddy simulation
Vorticity
vorticity
Spatial distribution
Tensors
spatial distribution
tendencies
inhomogeneity
Anisotropy

All Science Journal Classification (ASJC) codes

  • Computational Mechanics
  • Physics and Astronomy(all)
  • Mechanics of Materials
  • Condensed Matter Physics

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Turbulence structures over irregular rough surfaces. / Napoli, Enrico; De Marchis, Mauro; Armenio.

In: Journal of Turbulence, Vol. 11, 2010, pag. 1-32.

Risultato della ricerca: Article

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abstract = "Turbulent flow in a channel with irregular two-dimensional rough surfaces is analysed through wall-resolving large eddy simulation (LES). Both walls of the channel are roughened through the superimposition of sinusoidal functions having random amplitude and four different wavelengths. The downward shift of the velocity profile in the log region due to the roughness, known as roughness function, is well captured in the simulations. The spanwise and wall-normal turbulence intensities are found to increase with the roughness height, while the streamwise component decreases. The analysis of the Reynolds stress anisotropy tensor highlights a tendency towards isotropisation, confirmed by the vorticity rms. The analysis of the statistics shows that the effects of the roughness on the turbulent flow are greatly related to the increase of the height of the maximum peaks of the corrugations. Although the inner layer is dramatically affected by the wall irregularities, the outer layer appears not affected by the specific wall shape and a collapse of the turbulence statistics in smooth- and rough-wall conditions is observed. Much of the present results are consistent with the observations made over regular roughness, nevertheless the turbulence structures and the turbulent kinetic energy production analysis shows that the turbulence dynamics are directly affected by the local shape of the irregularities. The spatial inhomogeneities of the height of the roughness peaks and of the cavity region locally modifies the structures introducing variable length-scales. Overall the irregular roughness destroys the coherent pattern of the flow selectively, depending on the spatial distribution of the higher roughness peaks.",
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author = "Enrico Napoli and {De Marchis}, Mauro and Armenio",
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T1 - Turbulence structures over irregular rough surfaces

AU - Napoli, Enrico

AU - De Marchis, Mauro

AU - Armenio, null

PY - 2010

Y1 - 2010

N2 - Turbulent flow in a channel with irregular two-dimensional rough surfaces is analysed through wall-resolving large eddy simulation (LES). Both walls of the channel are roughened through the superimposition of sinusoidal functions having random amplitude and four different wavelengths. The downward shift of the velocity profile in the log region due to the roughness, known as roughness function, is well captured in the simulations. The spanwise and wall-normal turbulence intensities are found to increase with the roughness height, while the streamwise component decreases. The analysis of the Reynolds stress anisotropy tensor highlights a tendency towards isotropisation, confirmed by the vorticity rms. The analysis of the statistics shows that the effects of the roughness on the turbulent flow are greatly related to the increase of the height of the maximum peaks of the corrugations. Although the inner layer is dramatically affected by the wall irregularities, the outer layer appears not affected by the specific wall shape and a collapse of the turbulence statistics in smooth- and rough-wall conditions is observed. Much of the present results are consistent with the observations made over regular roughness, nevertheless the turbulence structures and the turbulent kinetic energy production analysis shows that the turbulence dynamics are directly affected by the local shape of the irregularities. The spatial inhomogeneities of the height of the roughness peaks and of the cavity region locally modifies the structures introducing variable length-scales. Overall the irregular roughness destroys the coherent pattern of the flow selectively, depending on the spatial distribution of the higher roughness peaks.

AB - Turbulent flow in a channel with irregular two-dimensional rough surfaces is analysed through wall-resolving large eddy simulation (LES). Both walls of the channel are roughened through the superimposition of sinusoidal functions having random amplitude and four different wavelengths. The downward shift of the velocity profile in the log region due to the roughness, known as roughness function, is well captured in the simulations. The spanwise and wall-normal turbulence intensities are found to increase with the roughness height, while the streamwise component decreases. The analysis of the Reynolds stress anisotropy tensor highlights a tendency towards isotropisation, confirmed by the vorticity rms. The analysis of the statistics shows that the effects of the roughness on the turbulent flow are greatly related to the increase of the height of the maximum peaks of the corrugations. Although the inner layer is dramatically affected by the wall irregularities, the outer layer appears not affected by the specific wall shape and a collapse of the turbulence statistics in smooth- and rough-wall conditions is observed. Much of the present results are consistent with the observations made over regular roughness, nevertheless the turbulence structures and the turbulent kinetic energy production analysis shows that the turbulence dynamics are directly affected by the local shape of the irregularities. The spatial inhomogeneities of the height of the roughness peaks and of the cavity region locally modifies the structures introducing variable length-scales. Overall the irregular roughness destroys the coherent pattern of the flow selectively, depending on the spatial distribution of the higher roughness peaks.

KW - irregular roughness; turbulence structures; channel flow; LES

UR - http://hdl.handle.net/10447/47748

M3 - Article

VL - 11

SP - 1

EP - 32

JO - Journal of Turbulence

JF - Journal of Turbulence

SN - 1468-5248

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