Variable Turbulent Schmidt and Prandtl Number Modeling

Goldberg, U.; Palaniswamy, S.; Batten, Paul; Gupta, Vinit

doi:10.1080/19942060.2010.11015337

Cited by 23 publications

(15 citation statements)

References 15 publications

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“…Goldberg et al [70] proposed an approach based on an extension of the [20] algebraic Reynolds stress model and relies on Reynolds stresses' anisotropy. The approach used these stresses to algebraically build velocity-scalar correlations, which were the starting point for a variable Sc t formulation.…”

Section: Environmental Flow Commentsmentioning

confidence: 99%

“…A second group of studies investigated the question if Sct is a constant or it is varying inside the flow domain [66,[70][71][72]. Koeltzsch [66] carried out wind tunnel experiments in a turbulent boundary layer above a flat plate.…”

Section: Contaminant Dispersion Due To Transverse Turbulent Mixing Inmentioning

confidence: 99%

“…Chen et al [60] Pollutant dispersion in the built environment Exp/Num − Sc t = 1.0 and corrected from wind tunnel data Hassan et al [65] Supersonic crossflow Exp/Num − Sc t = 1.0 and adaptive Sc t Galeazzo et al [64] Jet in crossflow Exp/Num − Sc t = 0.3-0.9 Goldberg et al [70] Different type of air flows Exp/Num − Sc t variable Ross [71] Flow over forested hills Exp/Num − Sc t = Sc t (z)…”

Section: Environmental Flow Commentsmentioning

confidence: 99%

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On the Values for the Turbulent Schmidt Number in Environmental Flows

Gualtieri

Angeloudis

Bombardelli

et al. 2017

Fluids

172

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Computational Fluid Dynamics (CFD) has consolidated as a tool to provide understanding and quantitative information regarding many complex environmental flows. The accuracy and reliability of CFD modelling results oftentimes come under scrutiny because of issues in the implementation of and input data for those simulations. Regarding the input data, if an approach based on the Reynolds-Averaged Navier-Stokes (RANS) equations is applied, the turbulent scalar fluxes are generally estimated by assuming the standard gradient diffusion hypothesis (SGDH), which requires the definition of the turbulent Schmidt number, Sc t (the ratio of momentum diffusivity to mass diffusivity in the turbulent flow). However, no universally-accepted values of this parameter have been established or, more importantly, methodologies for its computation have been provided. This paper firstly presents a review of previous studies about Sc t in environmental flows, involving both water and air systems. Secondly, three case studies are presented where the key role of a correct parameterization of the turbulent Schmidt number is pointed out. These include: (1) transverse mixing in a shallow water flow; (2) tracer transport in a contact tank; and (3) sediment transport in suspension. An overall picture on the use of the Schmidt number in CFD emerges from the paper.

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Section: Environmental Flow Commentsmentioning

confidence: 99%

Section: Contaminant Dispersion Due To Transverse Turbulent Mixing Inmentioning

confidence: 99%

Section: Environmental Flow Commentsmentioning

confidence: 99%

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On the Values for the Turbulent Schmidt Number in Environmental Flows

Gualtieri

Angeloudis

Bombardelli

et al. 2017

Fluids

172

View full text Add to dashboard Cite

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“…A variable Pr T model proposed by Xiao et al (2007) is found to improve SBLI results. Similar models are proposed by Sommer, So & Zhang (1993), Brinckman, Calhoon & Dash (2007) and Goldberg et al (2010). In another work, Bowersox (2009) presents the exact transport equation for the turbulent energy flux, and simplifies it to get an algebraic model in terms of gradients in mean quantities.…”

Section: Introductionmentioning

confidence: 88%

Turbulent energy flux generated by shock/homogeneous-turbulence interaction

2016

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High-speed turbulent flows with shock waves are characterized by high localized surface heat transfer rates. Computational predictions are often inaccurate due to the limitations in modelling of the unclosed turbulent energy flux in the highly non-equilibrium regions of shock interaction. In this paper, we investigate the turbulent energy flux generated when homogeneous isotropic turbulence passes through a nominally normal shock wave. We use linear interaction analysis where the incoming turbulence is idealized as being composed of a collection of two-dimensional planar vorticity waves, and the shock wave is taken to be a discontinuity. The nature of the postshock turbulent energy flux is predicted to be strongly dependent on the angle of incidence of the incoming waves. The energy flux correlation is also decomposed into its vortical, entropy and acoustic contributions to understand its rapid non-monotonic variation behind the shock. Three-dimensional statistics, calculated by integrating two-dimensional results over a prescribed upstream energy spectrum, are compared with available data from direct numerical simulations. A detailed budget of the governing equation is also considered in order to gain insight into the underlying physics.

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“…For turbulent flows, the mass diffusion is influenced mostly by the turbulent transport. This is determined by the turbulent Schmidt number, and measures the ratio of momentum and mass diffusivity (Goldberg, Palaniswamy, Batten, & Gupta, 2010;Reynolds, 1975;Tominaga & Stathopoulos, 2007;Yeung, Xu, & Sreenivasan, 2002). The turbulent Schmidt number is relatively insensitive to the molecular fluid properties, thus there is little reason to alter the default value of Sc t = 0.7 for any species (ANSYS R Fluent R , 2012).…”

Section: Species Transportmentioning

confidence: 99%

CFD simulations of polymer devolatilization in steam contactors

Gabor

Shindle

Chandy

2017

Engineering Applications of Computational Fluid Mechanics

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Removal of volatiles and other unwanted products in a polymer mix is a critical step in polymer manufacturing. This process serves many purposes, such as improvement in the physical and chemical properties of the polymer, elimination of odours, recovery of monomers and solvents, and fulfilment of environmental regulations. In this study, the mixture of polymer and solvent, or cement, is mixed with superheated steam which causes the unwanted solvent to evaporate. As the cement droplets lose solvent and dry out, they are ejected as cement 'crumb' from the mixing device. This process is modelled using computational fluid dynamics (CFD) to gain insight into the complex phenomena. The model simulates the heat transfer and phase changes associated with cement and steam, via 3D axisymmetric calculations. Using an Eulerian-Lagrangian approach, the superheated steam is modelled as the continuous phase and tracked in an Eulerian frame, while the cement droplets are treated using a Lagrangian tracking method, thus as a whole allowing us to track the particle sizes, temperatures, and solvent content. Furthermore, a parametric study is carried out to analyse the effect of initial polymer temperature on final polymer product. The simulation is carried out with three different initial polymer temperatures and the resulting solvent concentration, and the size of the cement particles between the three cases are compared. By increasing the cement operating temperature, the solvent concentration in the cement crumb is significantly lower, and the final cement crumb sizes shows a slight decrease, which indicates better production performance. Indeed, full 3D CFD calculations, presented to verify the axisymmetric assumption, show differences in the particle statistics, which could have implications for design considerations. Such studies can provide further insights into control parameters that can potentially enhance the efficiency of such a manufacturing process. ARTICLE HISTORY

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Variable Turbulent Schmidt and Prandtl Number Modeling

Cited by 23 publications

References 15 publications

On the Values for the Turbulent Schmidt Number in Environmental Flows

On the Values for the Turbulent Schmidt Number in Environmental Flows

Turbulent energy flux generated by shock/homogeneous-turbulence interaction

CFD simulations of polymer devolatilization in steam contactors

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