Turbulence structures over irregular rough surfaces

Enrico Napoli, Armenio, Mauro De Marchis

Risultato della ricerca: Article

37 Citazioni (Scopus)

Abstract

Turbulent flow in a channel with irregular two-dimensional rough surfaces is analysedthrough wall-resolving large eddy simulation (LES). Both walls of the channel areroughened through the superimposition of sinusoidal functions having random amplitudeand four different wavelengths. The downward shift of the velocity profile in thelog region due to the roughness, known as roughness function, is well captured in thesimulations. The spanwise and wall-normal turbulence intensities are found to increasewith the roughness height, while the streamwise component decreases. The analysisof the Reynolds stress anisotropy tensor highlights a tendency towards isotropisation,confirmed by the vorticity rms. The analysis of the statistics shows that the effects ofthe roughness on the turbulent flow are greatly related to the increase of the heightof the maximum peaks of the corrugations. Although the inner layer is dramaticallyaffected by the wall irregularities, the outer layer appears not affected by the specificwall shape and a collapse of the turbulence statistics in smooth- and rough-wall conditionsis observed. Much of the present results are consistent with the observationsmade over regular roughness, nevertheless the turbulence structures and the turbulentkinetic energy production analysis shows that the turbulence dynamics are directlyaffected by the local shape of the irregularities. The spatial inhomogeneities of theheight of the roughness peaks and of the cavity region locally modifies the structuresintroducing variable length-scales. Overall the irregular roughness destroys the coherentpattern of the flow selectively, depending on the spatial distribution of the higherroughness peaks.
Lingua originaleEnglish
pagine (da-a)1-32
Numero di pagine32
RivistaDefault journal
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
  • Condensed Matter Physics
  • Mechanics of Materials
  • Physics and Astronomy(all)

Cita questo

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

In: Default journal, Vol. 11, 2010, pag. 1-32.

Risultato della ricerca: Article

Napoli, E, Armenio & De Marchis, M 2010, 'Turbulence structures over irregular rough surfaces', Default journal, vol. 11, pagg. 1-32.
Napoli, Enrico ; Armenio ; De Marchis, Mauro. / Turbulence structures over irregular rough surfaces. In: Default journal. 2010 ; Vol. 11. pagg. 1-32.
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T1 - Turbulence structures over irregular rough surfaces

AU - Napoli, Enrico

AU - Armenio, null

AU - De Marchis, Mauro

PY - 2010

Y1 - 2010

N2 - Turbulent flow in a channel with irregular two-dimensional rough surfaces is analysedthrough wall-resolving large eddy simulation (LES). Both walls of the channel areroughened through the superimposition of sinusoidal functions having random amplitudeand four different wavelengths. The downward shift of the velocity profile in thelog region due to the roughness, known as roughness function, is well captured in thesimulations. The spanwise and wall-normal turbulence intensities are found to increasewith the roughness height, while the streamwise component decreases. The analysisof the Reynolds stress anisotropy tensor highlights a tendency towards isotropisation,confirmed by the vorticity rms. The analysis of the statistics shows that the effects ofthe roughness on the turbulent flow are greatly related to the increase of the heightof the maximum peaks of the corrugations. Although the inner layer is dramaticallyaffected by the wall irregularities, the outer layer appears not affected by the specificwall shape and a collapse of the turbulence statistics in smooth- and rough-wall conditionsis observed. Much of the present results are consistent with the observationsmade over regular roughness, nevertheless the turbulence structures and the turbulentkinetic energy production analysis shows that the turbulence dynamics are directlyaffected by the local shape of the irregularities. The spatial inhomogeneities of theheight of the roughness peaks and of the cavity region locally modifies the structuresintroducing variable length-scales. Overall the irregular roughness destroys the coherentpattern of the flow selectively, depending on the spatial distribution of the higherroughness peaks.

AB - Turbulent flow in a channel with irregular two-dimensional rough surfaces is analysedthrough wall-resolving large eddy simulation (LES). Both walls of the channel areroughened through the superimposition of sinusoidal functions having random amplitudeand four different wavelengths. The downward shift of the velocity profile in thelog region due to the roughness, known as roughness function, is well captured in thesimulations. The spanwise and wall-normal turbulence intensities are found to increasewith the roughness height, while the streamwise component decreases. The analysisof the Reynolds stress anisotropy tensor highlights a tendency towards isotropisation,confirmed by the vorticity rms. The analysis of the statistics shows that the effects ofthe roughness on the turbulent flow are greatly related to the increase of the heightof the maximum peaks of the corrugations. Although the inner layer is dramaticallyaffected by the wall irregularities, the outer layer appears not affected by the specificwall shape and a collapse of the turbulence statistics in smooth- and rough-wall conditionsis observed. Much of the present results are consistent with the observationsmade over regular roughness, nevertheless the turbulence structures and the turbulentkinetic energy production analysis shows that the turbulence dynamics are directlyaffected by the local shape of the irregularities. The spatial inhomogeneities of theheight of the roughness peaks and of the cavity region locally modifies the structuresintroducing variable length-scales. Overall the irregular roughness destroys the coherentpattern of the flow selectively, depending on the spatial distribution of the higherroughness peaks.

KW - LES

KW - channel flow

KW - irregular roughness

KW - turbulence structures

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

M3 - Article

VL - 11

SP - 1

EP - 32

JO - Default journal

JF - Default journal

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