Mechanical Engineering - The University of Texas at Austin

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TEXSTAN uses the Kays turbulent Prandtl number model, developed in detail in our textbook
CHMT. The model evolved from a simple conduction model for Pr_{t} that includes heat conduction to or from the turbulent element (eddy) as it moves. The following equation fits the available experimental data reasonably well

where Pe_{t} = (ε_{M}/ν) Pr is a turbulent Péclet number. C is an experimental constant equal to 0.3. The far-field value of the turbulent Prandtl number, Pr_{t,∞} , is set equal to 0.86 for gases and light liquids, and for Pr< 0.6 (liquid metals), the Weigand correction is applied

The Pr_{t} model has been calibrated for equilibrium turbulent boundary layers for use with the mixing-length turbulence model. It works equally well for turbulent flows with one- and 2-equation turbulence models. This option is not recommended for transitional boundary layer flows or flows with pressure gradients, or for liquids with Pr > 10-20.

Note, for turbulent mass transfer, the turbulent mass flux would be specified through a turbulent Schmidt number. However, there is currently no provision in TEXSTAN to input a turbulent Schmidt number.

The flag ktme identifies the turbulent Prandtl number model choices for computing the turbulent conductivity.

ktme | turbulence model for the energy equation |
---|---|

= 1 | constant turbulent Prandtl number; =0.85 |

= 2 | constant turbulent Prandtl number, = fxx |

= 3 | Kays variable turbulent Prandtl number model |

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