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ABSTRACT
Numerical assessment was performed to investigate the wall-adaptive features offered by two subgrid-scale (SGS) turbulence models: Wall-Adapting Local Eddy Viscosity (WALE) and Vreman against the Smagorinsky model. The gas temperature and velocity field predictions were enhanced using WALE over Smagorinsky, especially at the flaming and near-wall regions since WALE considers both strain and rotation rates of the turbulent structure and the turbulent viscosity approaches zero at the wall. Conversely, the simulation results by Vreman were under-predicted against the experimental data. The WALE model could notably enhance the simulation accuracy for large-scale compartment fires due to significant improvements of the flow diffusivity modeling.
Nomenclature
| Cp | = | specific heat of constant pressure |
| Cs | = | Smagorinsky model constant |
| Cw | = | WALE model constant |
| Cv | = | Vreman model constant |
| D* | = | characteristic length of the fire plume |
| Eb | = | blackbody radiation |
| g | = | gravitational acceleration |
| = | species standard heat of formation | |
| Ij | = | radiation intensities |
| k | = | turbulent kinetic energy |
| ka,g | = | gas radiative absorption coefficient |
| min | = | inflow mass flux |
| mout | = | outflow mass flux |
| p | = | pressure |
| Pr | = | molecular Prandtl number |
| Scø | = | molecular Schmidt number for scalar quantities |
| PrT | = | turbulent Prandtl number |
| ScT, ø | = | turbulent Schmidt number for scalar quantities |
| P(Z) | = | probability density function |
| = | heat release rate | |
| R | = | gas constant |
| R* | = | spatial resolution |
| Ru | = | universal gas constant |
| Srad | = | radiant heat energy |
| = | source term for scalar quantities | |
| T | = | temperature |
| Tref | = | reference temperature |
| ui, uj | = | velocity components along the x, y, z Cartesian directions |
| XF | = | fuel mass fraction |
| Yi | = | mass fraction |
| Wi | = | molecular weight |
| Z | = | instantaneous mixture fraction |
| Z″2 | = | variance of mixture fraction |
| α | = | soot particle nucleation rate for number density |
| β | = | soot coagulation rate |
| ϵ | = | dissipation rate of turbulent energy |
| ϕ | = | scalar properties |
| φ | = | general field-dependent variable |
| ρ | = | density |
| ρref | = | reference density |
| μ | = | molecular viscosity |
| μT | = | turbulent viscosity |
| ωT | = | filtered heat release rate |
| χ | = | instantaneous scalar dissipation |
| χo | = | local peak value of χ |
| Superscript | = | |
| − | = | spatial-averaged |
| = | Favre-averaged |
Nomenclature
| Cp | = | specific heat of constant pressure |
| Cs | = | Smagorinsky model constant |
| Cw | = | WALE model constant |
| Cv | = | Vreman model constant |
| D* | = | characteristic length of the fire plume |
| Eb | = | blackbody radiation |
| g | = | gravitational acceleration |
| = | species standard heat of formation | |
| Ij | = | radiation intensities |
| k | = | turbulent kinetic energy |
| ka,g | = | gas radiative absorption coefficient |
| min | = | inflow mass flux |
| mout | = | outflow mass flux |
| p | = | pressure |
| Pr | = | molecular Prandtl number |
| Scø | = | molecular Schmidt number for scalar quantities |
| PrT | = | turbulent Prandtl number |
| ScT, ø | = | turbulent Schmidt number for scalar quantities |
| P(Z) | = | probability density function |
| = | heat release rate | |
| R | = | gas constant |
| R* | = | spatial resolution |
| Ru | = | universal gas constant |
| Srad | = | radiant heat energy |
| = | source term for scalar quantities | |
| T | = | temperature |
| Tref | = | reference temperature |
| ui, uj | = | velocity components along the x, y, z Cartesian directions |
| XF | = | fuel mass fraction |
| Yi | = | mass fraction |
| Wi | = | molecular weight |
| Z | = | instantaneous mixture fraction |
| Z″2 | = | variance of mixture fraction |
| α | = | soot particle nucleation rate for number density |
| β | = | soot coagulation rate |
| ϵ | = | dissipation rate of turbulent energy |
| ϕ | = | scalar properties |
| φ | = | general field-dependent variable |
| ρ | = | density |
| ρref | = | reference density |
| μ | = | molecular viscosity |
| μT | = | turbulent viscosity |
| ωT | = | filtered heat release rate |
| χ | = | instantaneous scalar dissipation |
| χo | = | local peak value of χ |
| Superscript | = | |
| − | = | spatial-averaged |
| = | Favre-averaged |