Experimental study of a turbulent cross‐flow near a two‐dimensional rough wall with narrow apertures

Mokamati, Satya; Olson, James A.; Martinez, D. Mark; Gooding, Richard

doi:10.1002/aic.11575

Cited by 3 publications

(3 citation statements)

References 20 publications

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“…It was thus shown that the ratio of contour height to wire width controls the boundary layer thickness and turbulence intensity near the wall. In an early study, Mokamati et al [17] experimentally measured the streamwise and mean velocity fluctuations of turbulent flow over a rough wall with suction. The near-wall streamwise velocity fluctuations and local mean streamwise velocity were shown to be a strong function of the surface roughness, and the aperture and cross-flow velocities.…”

Section: Effect Of Wall Geometry Local Flows and Flocculation On Fibmentioning

confidence: 99%

Experimental study of a time‐varying turbulent cross‐flow near a two‐dimensional rough wall with narrow apertures

et al. 2014

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Turbulent flow over a rough wall with suction or blowing is an industrially important fluid mechanics problem. In the screening of wood pulp fibre suspensions, for example, turbulent flow is induced by a rotor adjacent to a slotted screen cylinder. To better understand the complex hydrodynamics in the critical region between the pulp screen rotor and the slotted screen wall, the stream-wise velocity and aperture velocities were measured using particle image velocimetry. The vortex generated above the aperture is shown to be strongly dependent on aperture velocity and wall roughness. The vortex diminishes in size at higher aperture velocities and increased exit layer height. The experiments also show that the reversal flow in the slot decreases with lower rotor speeds and increased mean slot velocities. This observation challenges the existing models of apertures being cleared by flow reversal driven by a Bernoulli-type suction pulse. In its place, this paper identifies elements of a more sophisticated flow model that considers the depletion of the zone below the rotor as well as the flow in the wake of the foil.

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Section: Effect Of Wall Geometry Local Flows and Flocculation On Fibmentioning

confidence: 99%

Experimental study of a time‐varying turbulent cross‐flow near a two‐dimensional rough wall with narrow apertures

et al. 2014

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“…The roughness function,

Δ B_{o}

, depends on type of roughness, such as sand, sand mixture, threads, and spheres. Examples of the form of

Δ B_{o}

are given by Mokamati et al…”

Section: Introductionmentioning

confidence: 99%

“…The roughness function, B o , depends on type of roughness, such as sand, sand mixture, threads, and spheres. Examples of the form of B o are given by Mokamati et al [10] A number of authors have examined the local flow field within the roughness elements either by direct flow visualization or through computation. [11][12][13][14][15][16] With flow over square-ribbed roughness elements, [17] phenomenologically characterized two distinct flow fields, that is, d-or k-type.…”

Section: Introductionmentioning

confidence: 99%

Turbulent couette flow between corrugated walls: The case with motion of one wall perpendicular to the corrugation cavities

et al. 2014

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In this work, we numerically examine the two dimensional flow of a Newtonian fluid in the gap formed between two opposing cavities. The fluid is driven by the motion of the upper cavity and the case considered represents a simplified version of the geometry found in Low Consistency (LC) refiners. Numerical studies were conducted in which we characterized the effect of gap size on the flow field. Then, we examine material transport between the cavities by introducing a passive scalar to represent the motion of tracer particles. A large number of unsteady simulations were conducted over the range of velocities and gap sizes. Over the range of parameters studied, we identify two characteristic flow fields, defined as either steady or unsteady.

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Numerical study of separated cross‐flow near a two‐dimensional rough wall with narrow apertures and suction

Mokamati

Olson

Gooding³

2010

Can J Chem Eng

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The turbulent flow (Re = 1.5 × 10 5 ) near a rough wall with narrow apertures has been numerically analysed to study the effect of the aperture geometry and wall suction on the flow characteristics. The aperture entry geometry is characterized by roughness height and roughness width. The roughness height is varied from 0.3 to 1.2 mm and roughness width is varied from 2.6 to 4.0 mm. The wall suction is characterized by slot velocity which is varied from 0.25 to 5 m/s. The flow characteristics in terms of fluid streamlines, flow resistance, wall pressure, and wall shear have been presented for several cases. The results show that the flow through the apertures is dominated by a separation vortex that covers the aperture. As roughness height increased (or slope of the roughness), the vortex size increased. With increasing wall suction, the vortex size decreased and moved towards the aperture opening. The flow resistance characterized by pressure drop across the aperture is significantly high for very low wall suction and it is increased with increasing roughness slope. At higher wall suction the slot velocity and roughness geometry has less influence on flow resistance. Wall pressure and skin friction coefficients are dependent on the ratio of roughness height to width.Le débit turbulent (Re = 1,5 × 10 5 ) près d'une paroi rugueuse avec orificesétroits a fait l'objet d'une analyse numérique afin d'étudier l'effet de la géométrie de l'orifice et de la succion de la paroi sur les caractéristiques du débit. La géométrieà l'entrée de l'orifice est caractérisée par la hauteur de la rugosité et la largeur de la rugosité. La hauteur de la rugosité variait de 0,3à 1,2 mm et la largeur de la rugosité de 2,6à 4,0 mm. La succion de la paroi est caractérisée par la vélocité de la fente qui variait de 0,25à 5 m/s. Les caractéristiques du débit en termes de lignes de courant du fluide, de résistance au débit, de pression de paroi et de cisaillement de paroi ontété présentées pour plusieurs cas. Les résultats montrent que le débit par les orifices est dominé par un vortex de séparation qui recouvre l'orifice.À mesure que la hauteur de la rugosité augmente (ou pente de la rugosité), le vortex augmente. En augmentant la succion de la paroi, le vortex diminue et se déplace vers l'ouverture de l'orifice. La résistance au débit caractérisée par une chute de pression au travers de l'orifice est significativementélevée en présence d'une succion de paroi très faible et augmente en présence d'une augmentation de la pente de la rugosité. En présence d'une succion de paroiélevée, la vélocité de la fente et la géométrie de la rugosité ont un moindre impact sur la résistance au débit. Les coefficients de pression de la paroi et le frottement du revêtement sont fonction du ratio hauteurà largeur de la rugosité.

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Experimental study of a turbulent cross‐flow near a two‐dimensional rough wall with narrow apertures

Cited by 3 publications

References 20 publications

Experimental study of a time‐varying turbulent cross‐flow near a two‐dimensional rough wall with narrow apertures

Experimental study of a time‐varying turbulent cross‐flow near a two‐dimensional rough wall with narrow apertures

Turbulent couette flow between corrugated walls: The case with motion of one wall perpendicular to the corrugation cavities

Numerical study of separated cross‐flow near a two‐dimensional rough wall with narrow apertures and suction

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