Turbulence characteristics of the Bödewadt layer in a large enclosed rotor-stator system

Randriamampianina, Anthony; Poncet, Sébastien

doi:10.1063/1.2204049

Cited by 17 publications

(9 citation statements)

References 50 publications

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“…On the rotor side, the fluid is arriving from smaller radii where the flow is laminar, while on the stator side, the fluid comes from larger radii where turbulence prevails. The low value of the maximum of the turbulent Reynolds number Re t = k 2 /(ν ) = 20.52 [5] confirms the weakly turbulent nature of this flow, to be compared with the value Re t = 352 obtained by Poncet et al [3] at Re = 10 6 with G = 23.89. Although the profiles from the simulation resemble the behavior obtained from velocity measurements for R * rr and R * θθ until r * = 0.68, the Direct Numerical Simulation (DNS) underestimates these two normal components towards the periphery of the cavity.…”

Section: Turbulence Fieldsupporting

confidence: 61%

“…They have simulated the fully turbulent flow in an infinite two-disk configuration and provided a detailed set of data to analyse the near-wall coherent structures [1]. The reader is referred to the work of Randriamampianina and Poncet [5] for a detailed review on both rotating disk flows and three-dimensional turbulent boundary layers (3DTBLs).…”

Section: Introductionmentioning

confidence: 99%

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Three-dimensional Turbulent Boundary Layer in a Shrouded Rotating System

Poncet

Randriamampianina

2007

Flow Turbulence Combust

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A three-dimensional direct numerical simulation is combined with a laboratory study to describe the turbulent flow in an enclosed annular rotor-stator cavity characterized by a large aspect ratio G = (b − a)/ h = 18.32 and a small radius ratio a/b = 0.152, where a and b are the inner and outer radii of the rotating disk and h is the interdisk spacing. The rotation rate considered is equivalent to the rotational Reynolds number Re = b 2 /ν = 9.5 × 10 4 (ν the kinematic viscosity of water). This corresponds to a value at which experiment has revealed that the stator boundary layer is turbulent, whereas the rotor boundary layer is still laminar. Comparisons of the computed solution with velocity measurements have given good agreement for the mean and turbulent fields. The results enhance evidence of weak turbulence by comparing the turbulence properties with available data in the literature (Lygren and Andersson, J Fluid Mech 426:297-326, 2001). An approximately self-similar boundary layer behavior is observed along the stator. The wall-normal variations of the structural parameter and of characteristic angles confirm that this boundary layer is three-dimensional. A quadrant analysis (Kang et al., Phys Fluids 10:2315-2322) of conditionally averaged velocities shows that the asymmetries obtained are dominated by Reynolds stress-producing events in the stator boundary layer. Moreover, Case 1 vortices (with a positive wall induced velocity) are found to be

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Section: Turbulence Fieldsupporting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Three-dimensional Turbulent Boundary Layer in a Shrouded Rotating System

Poncet

Randriamampianina

2007

Flow Turbulence Combust

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“…This related problem consists of a rotating disk and a stationary disk, shrouded by a cylindrical sidewall, and there may also be an inner cylindrical hub. [37][38][39][40][41][42] However, the motivation for these studies comes from applications in turbomachinery rather than interests in crossflow boundary layer instabilities, and the setups studied typically have the gap between the two disks being a very small fraction of their radius and the cylindrical shroud is stationary. These characteristics of the rotor-stator setup lead to the boundary layer on the rotating disk being turned into the interior by the presence of the stationary shroud, forming a free shear layer that under some conditions becomes unstable to azimuthal waves 43 or the free shear layer may be drawn ͑via Ekman suction type processes͒ into either the boundary layer on the rotating or stationary disk or even periodically flipping between the two.…”

Section: Discussionmentioning

confidence: 99%

Crossflow instability of finite Bödewadt flows: Transients and spiral waves

et al. 2009

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The flow in an enclosed rotating cylinder with a stationary lower end wall is investigated numerically. For fast rotation rates, the flow in the interior is primarily in the azimuthal direction, with an angular momentum distribution very close to that corresponding to solid-body rotation for about the inner-half radius. The differential rotation sets up a large-scale circulation that is primarily present in the boundary layers on the rotating top and sidewalls and the stationary bottom wall, with a very weak effusive component throughout the bulk interior providing a matching between the boundary layer flows on the top and bottom. The top end wall boundary layer has a profile that very closely matches the von Kármán solution for a rotating disk boundary layer; it is stable and very robust to finite disturbances for all rotation rates considered. The boundary layer on the stationary bottom end wall has a profile that agrees with the Bödewadt solution for a stationary disk with an ambient flow in solid-body rotation. This boundary layer is not robust, suffering crossflow instability to multiarmed spiral waves via a supercritical Hopf bifurcation, as well as being susceptible to axisymmetric circular waves that travel radially inward where the boundary layer profile is most inflectional. In the absence of any external forcing, the circular waves are transitory, but low amplitude forcing can sustain them indefinitely, whereas the spiral waves are essentially unaffected by the external forcing.

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“…The authors concluded that their study indicated that the features of 3DTBLs depend on the flow configuration in question. In two very recent studies, Randriamampianina and Poncet [21] and Poncet and Randriamampianina [22] performed an experimental and numerical (DNS) investigation of turbulence characteristics in an enclosed rotor-stator system. The typical reduction in the structure parameter and the non-alignment of the velocity gradient and turbulent shear stress angles were observed.…”

Section: Introductionmentioning

confidence: 99%

Turbulence in a three‐dimensional wall‐bounded shear flow

Holstad

Andersson

Pettersen

2009

Numerical Methods in Fluids

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SUMMARYA new turbulent flow with distinct three-dimensional characteristics has been designed in order to study the impact of mean-flow skewing on the turbulent coherent vortices and Reynolds-averaged statistics. The skewing of a unidirectional plane Couette flow was achieved by means of a spanwise pressure gradient. Direct numerical simulations of the statistically steady Couette-Poiseuille flow enabled in-depth explorations of the turbulence field in the skewed flow. The imposition of a modest spanwise gradient turned the mean flow about 8 • away from the original Couette flow direction and this turning angle remained nearly the same over the entire cross section. Nevertheless, a substantial non-alignment between the turbulent shear stress angle and the mean velocity gradient angle was observed. The structure parameter turned out to slightly exceed that in the pure Couette flow, contrary to the observations made in some other three-dimensional shear flows.Coherent flow structures, which are known to be associated with the Reynolds shear stress in near-wall regions, were identified by the 2 -criterion. Instantaneous and ensemble-averaged vortices resembled those found in the unidirectional Couette flow. In the skewed flow, however, the vortex structures were turned to align with the local mean-flow direction. The conventional symmetry between Case 1 and Case 2 vortices was broken due to the mean-flow three-dimensionality. The turning of the coherent vortices and the accompanying symmetry-breaking gave rise to secondary and tertiary turbulent shear stress components. By averaging the already ensemble-averaged shear stresses associated with Case 1 and Case 2 vortices in the homogeneous directions, a direct link between the educed near-wall structures and the Reynolds-averaged turbulent stresses was established. These observations provide evidence in support of the hypothesis that the structural model proposed for two-dimensional turbulent boundary layers remains valid also in flows with moderate mean three-dimensionality.

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Turbulence characteristics of the Bödewadt layer in a large enclosed rotor-stator system

Cited by 17 publications

References 50 publications

Three-dimensional Turbulent Boundary Layer in a Shrouded Rotating System

Three-dimensional Turbulent Boundary Layer in a Shrouded Rotating System

Crossflow instability of finite Bödewadt flows: Transients and spiral waves

Turbulence in a three‐dimensional wall‐bounded shear flow

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