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A critical-layer framework for turbulent pipe flow

McKEON, B. J. ; SHARMA, A. S.

Journal of fluid mechanics, 2010-09, Vol.658, p.336-382 [Periódico revisado por pares]

Cambridge, UK: Cambridge University Press

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  • Título:
    A critical-layer framework for turbulent pipe flow
  • Autor: McKEON, B. J. ; SHARMA, A. S.
  • Assuntos: Boundary layer ; Boundary layer and shear turbulence ; boundary layer receptivity ; boundary layer structure ; Computational fluid dynamics ; critical layers ; Exact sciences and technology ; Flow velocity ; Flows in ducts, channels, nozzles, and conduits ; Fluid dynamics ; Fluid flow ; Fluid mechanics ; Fundamental areas of phenomenology (including applications) ; Hydrodynamic stability ; Mathematical models ; Physics ; Pipe flow ; pipe flow boundary layer ; Receptivity ; Reynolds number ; Turbulence ; turbulence theory ; turbulent boundary layers ; Turbulent flow ; Turbulent flows, convection, and heat transfer ; Very large scale ; Walls
  • É parte de: Journal of fluid mechanics, 2010-09, Vol.658, p.336-382
  • Notas: istex:EC00C91038794C655437FEA59E66334994164ED3
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    ArticleID:00176
    PII:S002211201000176X
    ObjectType-Article-1
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    content type line 23
  • Descrição: A model-based description of the scaling and radial location of turbulent fluctuations in turbulent pipe flow is presented and used to illuminate the scaling behaviour of the very large scale motions. The model is derived by treating the nonlinearity in the perturbation equation (involving the Reynolds stress) as an unknown forcing, yielding a linear relationship between the velocity field response and this nonlinearity. We do not assume small perturbations. We examine propagating helical velocity response modes that are harmonic in the wall-parallel directions and in time, permitting comparison of our results to experimental data. The steady component of the velocity field that varies only in the wall-normal direction is identified as the turbulent mean profile. A singular value decomposition of the resolvent identifies the forcing shape that will lead to the largest velocity response at a given wavenumber–frequency combination. The hypothesis that these forcing shapes lead to response modes that will be dominant in turbulent pipe flow is tested by using physical arguments to constrain the range of wavenumbers and frequencies to those actually observed in experiments. An investigation of the most amplified velocity response at a given wavenumber–frequency combination reveals critical-layer-like behaviour reminiscent of the neutrally stable solutions of the Orr–Sommerfeld equation in linearly unstable flow. Two distinct regions in the flow where the influence of viscosity becomes important can be identified, namely wall layers that scale with R+1/2 and critical layers where the propagation velocity is equal to the local mean velocity, one of which scales with R+2/3 in pipe flow. This framework appears to be consistent with several scaling results in wall turbulence and reveals a mechanism by which the effects of viscosity can extend well beyond the immediate vicinity of the wall. The model reproduces inner scaling of the small scales near the wall and an approach to outer scaling in the flow interior. We use our analysis to make a first prediction that the appropriate scaling velocity for the very large scale motions is the centreline velocity, and show that this is in agreement with experimental results. Lastly, we interpret the wall modes as the motion required to meet the wall boundary condition, identifying the interaction between the critical and wall modes as a potential origin for an interaction between the large and small scales that has been observed in recent literature as an amplitude modulation of the near-wall turbulence by the very large scales.
  • Editor: Cambridge, UK: Cambridge University Press
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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