Low Reynolds Number Effects on the Inner Region of a Turbulent Boundary Layer

Ching, C.Y.; Djenidi, L.; Antonia, R. A.

doi:10.1007/978-3-642-79965-5_1

Cited by 3 publications

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“…Moreover, as the p.d.f.s for different values of Re look only self-similar without being superimposable, the increase of the zero-value probability might be attributed to the inner scaling becoming not fully appropriate at low Re. The inner scaling is known not to perform well near the onset of sustained turbulence (Ching, Djenidi & Antonia 1996). In other words, the data at hand do not yield any clear value of [τ z ] c to discriminate between laminar and turbulent, irrespective of the scaling used.…”

Section: Identification Of Partial Collapsementioning

confidence: 97%

Turbulence collapse in a suction boundary layer

et al. 2016

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Turbulence in the asymptotic suction boundary layer is investigated numerically at the verge of laminarisation using direct numerical simulation. Following an adiabatic protocol, the Reynolds number Re is decreased in small steps starting from a fully turbulent state until laminarisation is observed. Computations in a large numerical domain allow in principle for the possible coexistence of laminar and turbulent regions. However, contrary to other subcritical shear flows, no laminar-turbulent coexistence is observed, even near the onset of sustained turbulence. High-resolution computations suggest a critical Reynolds number Re g ≈ 270, below which turbulence collapses, based on observation times of O(10 5 ) inertial time units. During the laminarisation process, the turbulent flow fragments into a series of transient streamwise-elongated structures, whose interfaces do not display the characteristic obliqueness of classical laminar-turbulent patterns. The law of the wall, i.e. logarithmic scaling of the velocity profile, is retained down to Re g , suggesting a large-scale wall-normal transport absent in internal shear flows close to the onset. In order to test the effect of these large-scale structures on the near-wall region, an artificial volume force is added to damp spanwise and wall-normal fluctuations above y + = 100, in viscous units. Once the largest eddies have been suppressed by the forcing, and thus turbulence is confined to the near-wall region, oblique laminar-turbulent interfaces do emerge as in other wall-bounded flows, however only transiently. These results suggest that oblique stripes at the onset are a prevalent feature of internal shear flows, but will not occur in canonical boundary layers, including the spatially growing ones.

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