Ansys 12.0 CFX 官方教程 18.ppt

Appendix CRadiation Modeling
Introduction to CFX
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Radiation
Thermal radiation is ic radiation which arises as a result of a temperature difference between the surface of an object and its surrounding
Atrium Example
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The Radiative Transport Equation (RTE)
Describes the propagation of radiative energy through a media which is itself emitting radiation, absorbing radiation and scattering radiation.
integro-differential equation
(putationally expensive to solve)
Radiative Transport Equation
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Several radiation models are available which provide approximate solutions to the RTE
Each radiation model has its assumptions, limitations, and benefits
1) Rosseland Model (Diffusion Approximation Model)
2) P-1 Model (Gibb’s Model/Spherical Harmonics Model)
3) Discrete Transfer Model (Shah Model)
4) Monte Carlo Model (not available with the ANSYS CFD-Flo product)
Radiation Models
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The Rosseland Model
Method:
A new diffusion term is added to the energy equation
Limitations:
Only valid for optically thick and linearly anisotropic material (thickness/depth greater than 10)
Not va