Particle-generated turbulence in homogeneous dilute dispersed flows

Mizukami, Masashi; Parthasarathy, Ramkumar N.; Faeth, G. M.

doi:10.1016/0301-9322(92)90024-b

Cited by 52 publications

(42 citation statements)

References 12 publications

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“…A variety of flows ranging from homogeneous turbulence to pipe flow, channel flow, and jets have been studied. In many of these studies the particle size ranges from about the Kolmogorov scale up to the Taylor microscale ͑Tsuji et al, 22 Wu and Faeth, 9,10 Mizukami et al, 23 Parthasarathy and Faeth, 24 Yusof 6 ͒. In many of these studies the focus has been the interaction of turbulence with a distribution of large number of particles.…”

Section: Methodsmentioning

confidence: 99%

Effect of turbulence on the drag and lift of a particle

2003

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A direct numerical simulation ͑DNS͒ is used to study the effect of a freestream isotropic turbulent flow on the drag and lift forces on a spherical particle. The particle diameter is about 1.5-10 times the Kolmogorov scale, the particle Reynolds number is about 60-600, and the freestream turbulence intensity is about 10%-25%. The isotropic turbulent field considered here is stationary, i.e., frozen in time. It is shown that the freestream turbulence does not have a substantial and systematic effect on the time-averaged mean drag. The standard drag correlation based on the instantaneous or mean relative velocity results in a reasonably accurate prediction of the mean drag obtained from the DNS. However, the accuracy of prediction of the instantaneous drag decreases with increasing particle size. For the smaller particles, the low frequency oscillations in the DNS drag are well captured by the standard drag, but for the larger particles significant differences exist even for the low frequency components. Inclusion of the added-mass and history forces, computed based on the fluid velocity at the center of the particle, does not improve the prediction. Different estimates of the fluid velocity seen by the particle are examined. It is shown that the mean drag is insensitive to the fluid velocity measured at the particle center, or obtained by averaging over a fluid volume of the order of the particle size. The fluctuations diminish as the size of the averaging volume increases. The effect of increasing freestream turbulence intensity for the same particle size is studied. Fluctuations in the drag and lift forces are shown to scale with the mean drag and freestream intensity. The standard drag without the added-mass and history forces provides the best approximation to the DNS result.

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Section: Methodsmentioning

confidence: 99%

Effect of turbulence on the drag and lift of a particle

2003

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“…This correlation was obtained by fttting predictions of turbulence kinetic energy to data from experiments on homogeneous sedimenting and bubbly systems [22][23][24][25]. The term K 11 is the momentum exchange coefficient and the model will be discussed next.…”

Section: Turbulence Modelingmentioning

confidence: 99%

Simulating Gas-Liquid Flows in an External Loop Airlift Reactor

Law

Battaglia

Heindel

2008

Volume 10: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B, and C

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The external loop airlift reactor (ELALR) is a modified bubble column reactor that is composed of two vertical columns that are connected with two horizontal connectors. Airlift reactors are utilized in fermentation processes and are preferred over traditional bubble column reactors because they can operate over a wider range of conditions. Computational fluid dynamics (CFD) simulations can be used to enhance our understanding of the hydrodynamics within these reactors. In the present work, the gas-liquid flow dynamics in an external loop airlift reactor are simulated using CFDLib with an Eulerian-Eulerian ensembleaveraging method in two-dimensional (2D) and three-dimensional (3D) coordinate systems. In addition, models are employed for the interphase momentum transfer drag coefficient and turbulence behavior. The CFD simulations for temporal and spatial averaged gas holdup are compared to the experimental measurements of Jones and Heindel [1] who used a 10.2 cm diameter ELALR over a range of superficial gas velocities from 0.5 to 20 cm/s. The effect of specifying a mean bubble diameter size for the CFD modeling is examined. The objectives are to validate 2D and 3D CFD simulations with experimental data in order to predict the hydrodynamics in an airlift reactor for future studies on scale-up and design. ABSTRACTThe external loop airlift reactor (ELALR) is a modified bubble column reactor that is composed of two vertical columns that are connected with two horizontal connectors. Airlift reactors are utilized in fermentation processes and are preferred over traditional bubble column reactors because they can operate over a wider range of conditions. Computational fluid dynamics (CFD) simulations can be used to enhance our understanding of the hydrodynamics within these reactors. In the present work, the gas-liquid flow dynamics in an external loop airlift reactor are simulated using CFDLib with an Eulerian-Eulerian ensemble-averaging method in twodimensional (2D) and three-dimensional (3D) coordinate systems. In addition, models are employed for the interphase momentum transfer drag coefficient and turbulence behavior. The CFD simulations for temporal and spatial averaged gas holdup are compared to the experimental measurements of Jones and Heindel [I] who used a 10.2 em diameter ELALR over a range of superficial gas velocities from 0.5 to 20 cm/s. The effect of specifying a mean bubble diameter size for the CFD modeling is examined. The objectives are to validate 2D and 3D CFD simulations with experimental data in order to predict the hydrodynamics in an airlift reactor for future studies on scale-up and design.

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“…Early studies showed that turbulence generation by particles (drops) involved particle wakes embedded in a turbulent interwake region (Parthesarathy and Faeth 1990a,b;Mizukami et al 1992). ,1994 subsequently showed that the wakes behaved like laminar wakes but with fast mixing due to the presence of turbulence (commonly referred to as "laminar-like turbulent wakes").…”

Section: Primary Breakup Of Round Aerated-liquid Jets In Supersonic Gmentioning

confidence: 99%

Liquid Breakup in Dense Sprays

Faeth¹,

Dahm²

2006

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Particle-generated turbulence in homogeneous dilute dispersed flows

Cited by 52 publications

References 12 publications

Effect of turbulence on the drag and lift of a particle

Effect of turbulence on the drag and lift of a particle

Simulating Gas-Liquid Flows in an External Loop Airlift Reactor

Liquid Breakup in Dense Sprays

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