A Two-Way Coupled Model of Particle-Laden Turbulence

Skjæraasen, O.; Skartlien, R.; Zarruk, Gustavo A.

doi:10.1080/01932691.2014.1003069

Cited by 2 publications

(2 citation statements)

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“…The added mass force is important for bubbles and droplets in liquid where the particle mass density is smaller or comparable to that of the carrier fluid. The respective interaction terms emerge naturally in the kequation by considering the particle equation of motion (EOM) with the drag and added mass forces retained, and when considering appropriate volume and ensemble averaging (Skjaeraasen, Skartlien, and Zarruk, 2015).…”

Section: A Modelling Strategiesmentioning

confidence: 99%

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A generalized k-epsilon model for turbulence modulation in fluid-particle flows

Skartlien¹,

Palmer²,

Skjæraasen³

2022

Preprint

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A large amount of published data show that particles with diameter above 10% of the turbulence integral length scale (D/l > 0.1) tend to increase the turbulent kinetic energy of the carrier fluid above the singlephase value, and smaller particles tend to suppress it. A revised phenomenological model of the k − type was developed to reproduce these effects with the correct asymptotic limit of no turbulence modulation for small particles, and augmentation for larger diameter solids. Particle-kinetic theory was used to derive the work exchanged between the particles and the fluid due to both drag and added mass forces to accomodate any particle/fluid density ratios including bubbles, droplets and heavy solids. For the larger particles, we devised a new model for vortex shedding induced by the slip between the particles and the turbulent flow, due to particle inertia. Simple approximate formulae for the turbulence modulation were obtained through asymptotic analysis, for the purpose of application.The overall effect for solid particles is that augmentation for large diameter solids is due to vortex shedding, and turbulence suppression for small diameters is due to mainly to turbulent drag forces and extra fluid dissipation. The transition from suppression to augmentation around D/l = 0.1 is a robust feature for a wide range of particle Reynolds and Stokes numbers, but we could not prove this to be a general relation on a theoretical basis. Indeed, bubbles and droplets may not display turbulence augmentation at all for the larger diameters due to moderate turbulence levels needed to prevent breakup, and the velocity difference between particles and fluid may therefore be too low for vortex shedding to occur. On the basis of the model we find that some data for solids in vertical gas flow show very large turbulence augmentation that can only be due to gravitational settling rather than slip that is generated by the turbulent flow.

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Section: A Modelling Strategiesmentioning

confidence: 99%

“…The turbulent kinetic energy of the fluid-particle mix in stationary channel flow can be expressed by (Skjaeraasen, Skartlien, and Zarruk, 2015)…”

Section: B the K-equationmentioning

confidence: 99%