Two-layer turbulence model for heat transfer in wall turbulent shear flows
Two-equation {kappa}-{epsilon} and {kappa}{sub t}-{epsilon}{sub t} models are now popular and widely used tools for solving flow and heat transfer problems encountered in engineering applications. However, a model valid down to the wall needs a large number of grid points to obtain trustworthy variations in turbulent quantities near the wall. In addition, calculation instability often occurs in this type of model because the wall boundary conditions for {epsilon} and {epsilon}{sub t} are determined from the near-wall solutions for {kappa} and {kappa}{sub t}. In this study, the authors propose a new two-layer turbulence model based on the low-Reynolds-number {kappa}-{epsilon} and {kappa}{sub t}-{epsilon}{sub t} models so as to allow calculations to be stable and less costly. A new approach for the two-layer models is made on the basis of the time-scale modeling, which differs from the traditional approach based on the length-scale modeling. Thus, only dissipation-rates of turbulent energy and of temperature variance are modeled algebraically near the wall. Also, criterion functions to link the algebraic formulas to the transport equations are proposed. These criterion functions serve for connection between the algebraic formulas and equations near the wall in various flows with heat transfer including Prandtl number effects. The present models are tested in wall turbulent shear flows with heat transfer. In a variety of Prandtl number fluids, the present predictions show good agreement with the corresponding DNS data. The authors have also calculated a backward-facing step flow to assess the model performance in a complex flow. The predicted distributions of mean velocity and mean temperature are shown. It can be seen that the present model predicts well both profiles. The model predictions indicate that the agreement with the experiments and DNS data is very good, and the calculation stability achieved is remarkably high.
- Research Organization:
- Nagoya Inst. of Tech. (JP)
- OSTI ID:
- 20026760
- Country of Publication:
- United States
- Language:
- English
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