Numerical Models for Two-Phase Turbulent Flows

Crowe, C. T.; Troutt, T. R.; Chung, J. N.

doi:10.1146/annurev.fl.28.010196.000303

Cited by 524 publications

(232 citation statements)

References 66 publications

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“…11,32 This method assumes that the fluid velocity used in equation (5a) is constant during the time that a particle spends in an eddy and is taken as…”

Section: Governing Equations and Turbulence Modelsmentioning

confidence: 99%

Transport and Deposition of Micro-Aerosols in Realistic and Simplified Models of the Oral Airway

2007

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A number of in vivo, in vitro and numerical studies have considered flow field characteristics and micro-particle deposition in the oral airway extending from the mouth through the larynx. These studies have highlighted the effects of flow rates, turbulence and particle characteristics on deposition values in realistic and simplified geometries. However, the effect of geometry simplifications on regional and local deposition patterns remains largely un-quantified for the oral airway and throughout the respiratory tract. The objective of this study is to assess the effects of geometry simplifications on regionally averaged and local micro-aerosol deposition characteristics in models of the extrathoracic oral airway. To achieve this objective, a realistic model of the oral airway has been constructed based on CT scans of a healthy adult in conjunction with measurements reported in the literature. Three other geometries with descending degrees of physical realism were constructed based on successive geometric simplifications of the realistic model. A validated low Reynolds number (LRN) k-omega turbulence model was employed to simulate laminar, transitional and fully turbulent flow regimes for 1-31 microm particles. Geometric simplifications were found to have a significant effect on aerosol dynamics, hot spot formations and cellular-level deposition values in the extrathoracic airway models considered. For all models, regional deposition efficiency results were found to be approximately within one standard deviation of available experimental data when plotted as a function of Stokes number. The realistic geometry provided the best predictions of regional deposition in comparison to experimental data as a function of particle diameter. Considering localized deposition, maximum deposition enhancement factors, which represent the ratio of local to total deposition, were one to two orders of magnitude higher for the realistic model. Geometric factors that significantly contributed to enhanced particle localization in the realistic model include a triangular-shaped glottis and a dorsal-sloped trachea. Therefore, highly realistic models of the oral airway geometry may be necessary to evaluate localized deposition patterns and hot spot formations, which are critical for accurately predicting cellular-level dose.

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“…11,32 This method assumes that the fluid velocity used in equation (5a) is constant during the time that a particle spends in an eddy and is taken as…”

Section: Governing Equations and Turbulence Modelsmentioning

confidence: 99%

Transport and Deposition of Micro-Aerosols in Realistic and Simplified Models of the Oral Airway

2007

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“…Two-phase continuous mathematical models are feasible [1], but they require, among other things, the determination of closures for both the particle and the fluid stresses. In this Letter, we restrict our analysis to collisional suspensions, in which the particleimmersed weight is supported by collisions and the particle inertia is dominant [2][3][4].…”

mentioning

confidence: 99%

Turbulence Locality and Granularlike Fluid Shear Viscosity in Collisional Suspensions

Berzi

Fraccarollo

2015

Phys. Rev. Lett.

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We reanalyze previous experimental measurements of solid volume fraction, mean velocity, and velocity fluctuations in collisional suspensions of plastic cylinders and water flowing over inclined, erodible beds. We show that the particle pressure scales with the granular temperature, as predicted by kinetic theory of granular gases. The assumption that the particle shear stress is also well predicted by kinetic theory permits us to determine the fluid shear stress and the effective fluid viscosity from the experiments. The fluid viscosity can be decomposed into turbulent and granularlike components: the turbulent viscosity can be modeled using a mixing length, which is a decreasing function of the local volume fraction and does not depend upon the distance from the bed; the granularlike viscosity, associated with the transfer of momentum due to the conjugate motion of the fluid mass added to the particles, can be modeled by replacing the particle density with the density of the added fluid mass in the viscosity of kinetic theory.

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“…The equation of motion for the particles is the BassetBoussinesq-Oseen (BBO) equation [31]. As reported in the literature [32,33], most of the terms in this equation can be neglected in dilute gas-solid flows. Therefore we use a reduced form of the equation:…”

Section: Particle Trackingmentioning

confidence: 99%

Particle tracking and particle–shock interaction in compressible-flow computations with the V-SGS stabilization and $$YZ\beta $$ Y Z β shock-capturing

et al. 2015

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The Y Zβ shock-capturing technique, which is residual-based, was introduced in conjunction with the Streamline-Upwind/Petrov-Galerkin (SUPG) formulation of compressible flows in conservation variables. It was later also combined with the variable subgrid scale (V-SGS) formulation of compressible flows in conservation variables and successfully tested on 2D and 3D computation of inviscid flows with shocks. In this paper we extend that combined method to inviscid flow computations with particle tracking and particle-shock interaction. Particles are tracked individually, assuming one-way dependence between the particle dynamics and the flow. We present two steady-state test computations with particle-shock interaction, one in 2D and one in 3D, and show that the overall method is effective in particle tracking and particle-shock interaction analysis in compressible flows.

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Numerical Models for Two-Phase Turbulent Flows

Cited by 524 publications

References 66 publications

Transport and Deposition of Micro-Aerosols in Realistic and Simplified Models of the Oral Airway

Transport and Deposition of Micro-Aerosols in Realistic and Simplified Models of the Oral Airway

Turbulence Locality and Granularlike Fluid Shear Viscosity in Collisional Suspensions

Particle tracking and particle–shock interaction in compressible-flow computations with the V-SGS stabilization and $$YZ\beta $$ Y Z β shock-capturing

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