Computing radiative heat transport by ray tracing method

To use the ray tracing based radiation model one has to do some preparative work before starting a simulation.

  1. The first thing to do is to define the semitransparent material and it's material properties (see Material Dialog). The material properties are supposed to be constant in some wavelength domains called spectral bands. A semitransparent material can have a combination of transparent, semitransparent and opaque bands and this should be defined accordingly. The opaque bands are deduced from the semitransparent and transparent ones.

    To define a material as semitransparent (or participating media) one has to chose the Participating Media as a Transparency in Material dialogue and define the rest of the material properties accordingly. The transparent and/or semitransparent bands are to be given in um and should be a list of space separated values like for example for two bands from 1.2 until 3 μm and from 5 until 7 μm: "1.2-3 5-7". A material with Transparency windows defined as: 2-5 and Semitransparent windows defined as 1-2 5-7, will be a material transparent between 2-5μm, semitransparent between 1-2 and 5-7μm and opaque in the rest of the spectrum (i. e. in two spectral bands 0-1 and 7-infinity in μm). The absorption coefficient is supposed to be constant inside a semitransparent band so it should be introduced as a list of space separated values (e.g. 10 20.3 30). The number of values for the absorption coefficient should be equal to the number of the defined semitranmsparent bands. Failing to do so will be promptly informed by CrysMAS.

    Material dialogue showing the optical material properties. 

    Figure 115.  Material dialogue showing the optical material properties.

  2. After defining the material properties and assignment of this material to some regions one has to activate the computation of the Integrated Intensity in that regions in order to be able to start a simulation that takes into account the participating media effects.

    To activate the computation of the Integrated Intensity select the region having the semitransparent material in it and go to Settings-> Physical Phenomena and click the check box that activates (Yes) the computation of the integrated intensity variable group.

  3. Before computing the intensities and/or temperature the first step is to do the data preparation for computational ray tracing, it means the geometrical tracing of ray paths.

    This can be done either in a separate step by choosing from the menu Computation -> Start Tracing Rays or together with the computation of the temperature or intensity by clicking on the Start Computation button.

    To compute only the intensities for a given temperature field one has to chose from the graphical user interface Integrated Intensity as the current variable group and after that press the Start Computation button or chose Start Computation from the Computation menu.

  4. The accuracy of the numerical solution can be influenced by the following parameters to be found on the Computation -> Numerical Parameters dialog in the Radiation tab shown in the figure below:

    Ray Subdivision Factor

    which multiplies the default number of ray subdivisions computed inside the program and

    the numbers of directions

    resulting from the space angle discretization. One can chose between medium, high and huge but take into account that also the simulation time will increase. Usually the medium space angle discretization produces solution for temperature which is not more significantly dependent on the space angle discretization.

    Input dialog for definition of the radiation model parameters 

    Figure 116. Input dialog for definition of the radiation model parameters

The following variables are available when choosing the Integrated Intensity Group: