Particle-turbulence interaction in a boundary layer

Rashidi, M. M.; Hetsroni, G.; Banerjee, Sanjoy

doi:10.1016/0301-9322(90)90099-5

Cited by 266 publications

(147 citation statements)

References 18 publications

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“…Their result shows that the streamwise turbulence intensities of water and sand are practically the same, whereas the vertical sediment turbulence intensities are dampened throughout the flow depth, which are more pronounced near the bed. The existence of the slip velocity between the fluid and particle phases has been reported by, for example, Sumer and Deigaard [1981], Rashidi et al [1990], Wang and Ni [1991], Kaftori et al [1995], and Taniere et al [1997]. The measurements by Graf [1999a, 1999b] using a nonintrusive sonar instrument indicate that turbulence is suppressed by suspended sediment.…”

Section: Turbulence Modulation By Suspended Sedimentmentioning

confidence: 90%

Role of suspended‐sediment particle size in modifying velocity profiles in open channel flows

Cao

Egashira

Carling

2003

Water Resources Research

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.[1] Previous experimental and analytical studies have revealed that suspended particles can attenuate or enhance turbulence, depending on the particle size in relation to turbulence scales. Incorporating this mechanism, an empirical turbulent eddy viscositybased closure model is proposed for the mean velocity structure of suspended sedimentladen flow in open channels. The model integrates the sediment particle Stokes number, the ratio of particle-size-to-turbulence microscale, the ratio of particle settling velocity to bed shear velocity, and local sediment concentration. Its good performance is demonstrated in comparison with available laboratory observations. It is characterized that single-phase turbulence closure models can be adapted for sediment-laden flows by implementing sediment particle size effects.

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Section: Turbulence Modulation By Suspended Sedimentmentioning

confidence: 90%

Role of suspended‐sediment particle size in modifying velocity profiles in open channel flows

Cao

Egashira

Carling

2003

Water Resources Research

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“…Evidence for such dynamics comes from the observation of longitudinal streaks for the case of sediment-laden flows, including those over rough beds (Grass 1971). Sumer & Deigaard (1981), Yung, Merry & Bott (1989), Rashidi, Hetsroni & Banerjee (1990), Garcia, Nino & Lopez (1995) and provided convincing experimental evidence of the influence of bursts on the incipient movement of solid particles. Pressure fluctuations caused by turbulent eddies could provide a physical explanation of the connection between particle entrainment and coherent structures.…”

Section: Bulk Statisticsmentioning

confidence: 97%

Pressure forces on sediment particles in turbulent open-channel flow: a laboratory study

2014

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An experimental investigation into the fluctuating pressure acting on sediment particles on the bed of an open-channel flow was carried out in a large laboratory flume for a range of flow depths and bed slopes. The pressure measurements were made using 23 spherical particles instrumented with differential pressure sensors. These measurements were complemented with simultaneous measurements of the velocity field using high-resolution stereoscopic particle image velocimetry. The pressure statistics show that the standard deviations of the drag and lift fluctuations vary from 2.0 to 2.6 and from 2.5 to 3.4 times the wall shear stress, respectively, and are dependent on relative submergence and flow Reynolds number. The skewness is positive for the drag fluctuations and negative for the lift fluctuations. The kurtosis values of both drag and lift fluctuations increase with particle submergence. The two-particle correlation between drag and lift fluctuations is found to be relatively weak compared to the two-point drag-drag and lift-lift correlations. The pressure cross-correlations between particles separated in the longitudinal direction exhibit maxima at certain time delays corresponding to the convection velocities varying from 0.64 to 0.72 times the bulk flow velocity, being very close to the near-bed eddy convection velocities. The temporal autocorrelation of drag fluctuations decays much faster than that for the lift fluctuations; as a result, the temporal scales of lift fluctuations are 3-6 times that of drag fluctuations. The spatial and temporal scales of both drag and lift fluctuations show dependence on flow depth and bed slope. The spectral behaviour of both drag and lift fluctuations is also assessed. A f −11/3 slope is observed for the spectra of the drag fluctuations over the majority of the frequency range, whereas the lift spectra suggest two scaling ranges, following a f −11/3 slope at high frequencies and f −5/3 behaviour at lower frequencies.

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“…3,4 Evidence of drag reduction achieved by means of spherical particles is, however, almost nonexisting. Rashidi et al 18 showed that the presence of small particles reduced the number of wall ejections, turbulence intensity, and also the skin friction. A modest pressure-loss reduction was also reported for the smallest particle case considered in the pipe-flow experiments by Kartushinsky et al 19 More recent pressure-drop measurements by Bari and Yunus 20 showed substantial drag reduction for suspensions of either alumina or sand particles in kerosene over a fairly wide range of turbulent Reynolds numbers.…”

mentioning

confidence: 99%

Turbulence modulation and drag reduction by spherical particles

Zhao

Andersson²,

Gillissen³

2010

Physics of Fluids

123

110

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This letter reports on the pronounced turbulence modulations and the accompanying drag reduction observed in a two-way coupled simulation of particle-laden channel flow. The present results support the view that drag reduction can be achieved not only by means of polymeric or fiber additives but also with spherical particles. © 2010 American Institute of Physics. ͓doi:10.1063/1.3478308͔The inevitable pressure loss associated with transport of fluids in pipelines determines the pumping requirements. The pressure loss arises in order to overcome the skin-friction drag. Several investigations of turbulent drag reduction have thus been motivated by the economical benefits of pressureloss reduction. Drag reduction can be achieved in many different ways, for instance, by means of additives suspended into an otherwise Newtonian fluid ͑see, e.g., the reviews by Lumley 1 and Gyr and Bewersdorff 2 ͒. A notable example is the substantial drag reduction observed when flexible polymers are dissolved in the carrier fluid as reported in Refs. 3 and 4 ͑see also the recent reviews 5,6 ͒. However, the findings with respect to drag reduction are not as clear-cut for additives other than polymers and chemicals. Pressure drop measurements reported from a variety of solid-fluid systems were scrutinized by Radin et al. 7 While drag reduction was obtained with fibrous additives ͑e.g., nylon or cotton͒, no drag reduction was reported for nonfibrous additives irrespective of the shape of the solid ͑spherical, platelet, or needle-shaped͒. More recently, drag reduction has been reported from computer experiments by Paschkewitz et al. 8 and Gillissen et al.9 also for rigid fibers. Suspensions of spherical particles in turbulent pipe and channel flows have been extensively studied during the years with the view to better understand the particle transport, dispersion, and segregation in wall-turbulence and also the influence of the presence of the solid spheres on the turbulence of the carrier fluid. The current understanding of the complex behavior of inertial spherical particles in turbulent wall flows was summarized in a keynote lecture by Soldati. 10 The survey of experimental studies and two-way coupled computer simulations by Balachandar and Eaton 11 furthermore addressed the turbulence modulation observed in the presence of inertial particles. In dilute suspensions where particle collisions are of negligible importance, the fluid turbulence may be affected by an enhanced dissipation due to the particles, kinetic energy transfer between the fluid and the particles, and wakes formed in the lee of the solid particles. The relative importance of these mechanisms depends on the particle Reynolds number, the particle-to-fluid density ratio, and the particle-to-turbulence length-scale ratio. By adopting the turbulence intensity as a measure of the turbulence activity, Gore and Crowe 12 showed that a particle diameter of 1/10 the size of the most energetic eddies represents a demarcation between increase and decrease of the carrier-phase tur...

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Particle-turbulence interaction in a boundary layer

Cited by 266 publications

References 18 publications

Role of suspended‐sediment particle size in modifying velocity profiles in open channel flows

Role of suspended‐sediment particle size in modifying velocity profiles in open channel flows

Pressure forces on sediment particles in turbulent open-channel flow: a laboratory study

Turbulence modulation and drag reduction by spherical particles

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