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12.3.8 Convective Heat and Mass Transfer Modeling

In FLUENT, turbulent heat transport is modeled using the concept of Reynolds' analogy to turbulent momentum transfer. The "modeled'' energy equation is thus given by the following:

 \frac{\partial}{\partial t} (\rho E) + \frac{\partial}{\par... ...al T}{\partial x_j} + u_i (\tau_{ij})_{\rm eff} \right] + S_h (12.3-18)

where $k$, in this case, is the thermal conductivity, $E$ is the total energy, and $(\tau_{ij})_{\rm eff}$ is the deviatoric stress tensor, defined as

(\tau_{ij})_{\rm eff} = \mu_{\rm eff} \left(\frac{\partial u_... ...} \mu_{\rm eff} \frac{\partial u_k}{\partial x_k} \delta_{ij}

The term involving $(\tau_{ij})_{\rm eff}$ represents the viscous heating, and is always computed in the density-based solvers. It is not computed by default in the pressure-based solver, but it can be enabled in the Viscous Model panel. The default value of the turbulent Prandtl number is 0.85. You can change the value of Pr $_t$ in the Viscous Model panel.

Turbulent mass transfer is treated similarly, with a default turbulent Schmidt number of 0.7. This default value can be changed in the Viscous Model panel.

Wall boundary conditions for scalar transport are handled analogously to momentum, using the appropriate "law-of-the-wall''.


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