Solver: Models

Radiation

CFX-Radiation is used by engineers and scientists throughout industry on a wide range of thermal and combustion problems including fire propagation, burners and furnaces, and solar heating.

Calculation Methods

Rosseland Model

The Rosseland approximation method assumes that the media is optically thick and that radiant energy emitted from other locations in the domain are quickly absorbed and have no influence in the local transport. This implies that the approximation is not valid near walls. In ANSYS CFX, special treatment is applied to wall boundaries to over come this limitation. Other boundaries are not given any special treatment. This approximation is extremely convenient to use since it does not solve for an additional transport equation.

P-1 Model

The Differential Approximation or P1 method (also known as Gibb’s model or Spherical Harmonics) adds an additional transport equation to the simulation. This model has proved adequate for the study of pulverized fuel (PF) flames in regions away from the immediate vicinity of the flame.

Monte Carlo Model

The Monte Carlo method simulates the physical interactions between photons and their environment. A number of photon histories are calculated which are representative of the true photon flux. The photon sources are sampled at random on the basis of luminosity and trajectory, and the statistical validity of the solution increases with the number of histories calculated.

Discrete Transfer Model

For models where the radiation field is expected to be reasonably homogeneous everywhere, the Discrete Transfer method can be used. This method is a mixture of the flux type methods and Monte Carlo with a fixed sampling. The Discrete Transfer method, when applicable, is faster computationally than Monte Carlo, especially when the same geometry is used repetitively, for example in combined flow-radiation calculations.

Sub models

Spectral

In CFX, three different spectral models are supported: Gray, Multiband, and Multigray or Weighted Sum of Gray Gases.

Scattering

The radiative transfer equation includes two terms due to scattering: attenuation by scattering or out-scattering and augmentation by scattering or in-scattering. When using the Monte Carlo radiation model, you can optionally specify a scattering model.

CFX simulation of the air flow and gas temperature in a swirling turbulent diffusion flame.

High-performance computing in industrial safety. Scale model of the HGV shuttle.
Courtesy of HSL

Gas temperature of the three concentric air inlets and coal-particle tracks from two of the four pulverized coal.