| 1. |
- Benavides, Aldo, 1978, et al.
(författare)
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Comparison of experimental and simulation results for turbulent gas-solid riser flow
- 2008
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Ingår i: Circulating Fluidized Bed Technology IX. Proceedings of the 9th International Conference on Circulating Fluidized Beds, CFB-9. May 13-16, 2008. Hamburg, Germany..
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Konferensbidrag (refereegranskat)abstract
- This paper compares measurements of the radial solids concentration in a riser with CFD simulations. An Eulerian model based upon the kinetic theory for granular flow, extended with models describing turbulence modulation and dispersion, is used to treat the particulate phase. Coupling between momentum equations of the gas and particulate phases is taken into account via a mean drag force formulation. Solids distribution profiles over three horizontal planes are measured by the use of optical probes. The pressure drop is used to estimate an average solids concentration profile along the riser. The comparison is reported for a single superficial gas velocity and solids mass flux.
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| 2. |
- Benavides, Aldo, 1978
(författare)
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Eulerian-Eulerian Modeling of Turbulent Gas-Particle Flow
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gas-particle flow is encountered in a vast number of industrial operations and natural phenomena. Computational fluid dynamics plays an important role in practical engineering and fundamental research activities. For the numerical prediction of gas-particle two-phase flow, an Eulerian approach is employed in this work so as to describe the particulate-phase as a continuum medium with properties analogous to those of a fluid. In addition, kinetic theory of granular flow is used to derive closure relations that take into account particle-particle interaction and interstitial fluid effects. Two-way coupling considers momentum transfer from the dispersed particulate-phase to the continuous gas-phase through appropriate source terms in the momentum and turbulent kinetic energy conservation equations. A modified k-ε model is used to estimate the continuous phase turbulence. Balance of kinetic energy associated with particle random motion and the correlation between fluid-and-particle fluctuating velocity are also incorporated. Friction plays an important role in determining gas-particle flow at very high particulate-phase concentration, so the development of a frictional stress model is also discussed.The derived two-phase flow model is used for the prediction of dilute turbulent gas-particle flow in a backward-facing step and a cold CFB-riser. The study of dense particle flow restricts to the formation of a cavity in a granular bed by an impinging turbulent jet. Closure models are implemented in a commercial CFD software, and simulation results are thoroughly validated with available experimental data.
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| 3. |
- Benavides, Aldo, 1978, et al.
(författare)
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Eulerian-Eulerian prediction of dilute turbulent gas-particle flow in a backward-facing step
- 2009
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Ingår i: International Journal of Heat and Fluid Flow. - : Elsevier BV. - 0142-727X. ; 30:3, s. 452-461
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Tidskriftsartikel (refereegranskat)abstract
- A numerical study of turbulent gas-particle flow in a two-dimensional, vertically oriented backward-facing step is compared with literature data. The dispersed phase is modeled by an Eulerian approach based upon the kinetic theory of granular flow (KTGF) including models for describing the dispersed phase interactions with the continuous phase. The modeling of turbulent motion within the dispersed phase and the correlation between gas and particle velocity fluctuations are discussed. In addition, closure relations for the dispersed phase are extended to incorporate interstitial fluid effects. The continuous phase turbulence is modeled by a kappa - epsilon model. This work demonstrates that treatment of turbulent characteristics is a key element in predicting the dispersed phase mean motion and turbulence modulation in the continuous phase. The derived models are implemented in a commercial code and simulation results are compared with benchmark experimental data for three particle classes with distinctive particle Stokes number, particle Reynolds number and mass-loading. In general, reasonable predictions are achieved. (c) 2009 Elsevier Inc. All rights reserved.
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| 4. |
- Benavides, Aldo, 1978, et al.
(författare)
-
Numerical computation of turbulent gas-particle flow in a backward-facing step
- 2008
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Ingår i: Proceedings 7th International Symposium on Engineering Turbulence Modelling and Measurements - ETMM7. Limassol, Cyprus, 4-6 June 2008.. ; 1, s. 144-149
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the present article, a numerical study of turbulent gas-particle flow in a vertically oriented backward-facing step is compared with literature data. The dispersed phase is simulated by an Eulerian approach based upon the kinetic theory for granular flow, including interaction with the continuous phase. The modeling of turbulent motion within the dispersed phase as well as the correlation between gas and particle velocity fluctuations are discussed. This work demonstrates that treatment of such quantities is essential to correctly describe the particulate phase distribution and turbulence modulation in the gas phase. In addition, closure relations for the dispersed phase are extended to incorporate the influence of the continuous fluid. The derived models are validated with benchmark experimental results of a planar sudden expansion turbulent flow including particles. In general, good agreement is found between model predictions and experimental data.
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| 5. |
- Benavides, Aldo, 1978, et al.
(författare)
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Numerical computation of turbulent gas-particle flow in a backward-facing step. Model comparison with experimental data
- 2008
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Ingår i: Proceedings 11th International Conference on Multiphase Flow in Industrial Plants, MFIP 2008. September 7-10, Palermo, Italy.. - 888819813X ; , s. 63-70
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Konferensbidrag (refereegranskat)abstract
- In the present article, the predictions of two models describing turbulent gas-particle flow in a vertically oriented backward-facing step are compared to each other and with literature data. The first model is an Eulerian approach based upon the kinetic theory of granular flow, including turbulence modulation and interaction with the continuous phase. The gas-phase turbulence is predicted by use of a k-epsilon dispersed turbulence model, including inter-phase energy transfer between gas and particle fluctuating motions. The second model also uses an Eulerian approach coupled to a k-omega turbulence model. The latter model considers the transport of particles to the near-wall region due to turbulence intensity gradients, and particulate phase influences on the gas flow. It is shown that the combined effect has an impact on the two-phase flow. The derived models are validated with benchmark experimental results of a planar sudden expansion turbulent flow including particles.
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| 6. |
- Benavides, Aldo, 1978
(författare)
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Numerical Modeling of Turbulent Gas-Particle Flow
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work presents a theoretical and numerical study of gas-particle two-phase flow within the Eulerian framework. Although gas-particle flows have been extensively studied, there is still no general agreement on the constitutive equations for an Eulerian-Eulerian model in which the dispersed phase is treated as a continuum, i.e. a granular fluid. To successfully simulate the averaged behavior of a gas-particle flow system, it is necessary to account for the fluctuating motion present in each phase. Kinetic theory of granular flow is commonly employed to derive appropriate dispersed phase properties in which the mean kinetic energy associated with particle velocity fluctuations plays a major role. In addition, collisions are considered as an important means of momentum and energy transfer within the dispersed phase. The influence of the interstitial gas on the particulate phase constitutive relations is also taken into account. It is shown that interphase coupling terms arise from the decomposed and averaged transport equations. The equations for mean quantities are used to introduce the closure models, mainly for the fluctuating kinetic energy relative to each phase. This is a more fundamental approach than assuming a standard k-ε model, with additional heuristic terms, as employed in most research work on turbulent gas-particle flow. As a result, attention is devoted to the influence of turbulence on dispersed phase mean quantities and turbulence modulation. Numerical simulations of fully developed turbulent gas-particle flow in a vertical pipe and a backward-facing step are validated with benchmark experimental measurements.
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| 7. |
- Benavides, Aldo, 1978, et al.
(författare)
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Numerical simulation and validation of dilute turbulent gas-particle flow with inelastic collisions and turbulence modulation
- 2008
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 182:2, s. 294-306
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Tidskriftsartikel (refereegranskat)abstract
- This work describes a theoretical and numerical study of turbulent gas-particle flows in the Eulerian framework. The equations describing the flow are derived employing Favre averaging. The closures required for the equations describing the particulate phase are derived from the kinetic theory of granular flow. The kinetic theory proposed originally is extended to incorporate the effects of the continuous fluid on the particulate phase behavior. Models describing the coupling between the continuous phase kinetic energy and particulate phase granular temperature are derived, discussed, and their effect on the flow predictions is shown.The derived models are validated with benchmark experimental results of a fully developed turbulent gas-solid flow in a vertical pipe. The effect of the models describing the influence of turbulence on the particle motion as well as the turbulence modulation due to the presence of particles is analyzed and discussed.
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| 8. |
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