Illuminated Surface
Use the Illuminated Surface node to release rays under the assumption that the emitted rays are specularly reflected from an external radiation source. It is assumed that the entire selected surface has direct line of sight to the external radiation source; that is, shadowing due to other geometric entities is not taken into account.
See Release for information on the following sections: Release Times, Initial Ray Frequency, Vacuum Wavelength, Initial Phase, Initial Polarization, and Initial Value of Auxiliary Dependent Variables.
See Release from Boundary for information on the Initial Position section.
Ray Direction Vector
Select the Rays to release: Reflected (the default) or Refracted.
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For Reflected select the Reflection coefficient specification: Using absorption coefficient (the default) or Using refractive indices. For Using absorption coefficient, if the Specify different values for s- and p-polarization check box is selected, you can instead enter separate values for the absorption of p- and s-polarized light, called αp and αs, respectively.
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For Refracted enter a value for Refractive index of exterior domains next (dimensionless). The default is 1. This index is absolute (that is, relative to vacuum).
Select an Incident ray direction vector: User-defined direction (the default), User-defined point source, or Solar radiation (3D components only).
Then based on the selection enter the applicable information:
For User-defined direction enter the components of the Incident ray direction vector Li (dimensionless) based on space dimension.
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For User-defined point source enter the Point source location rsrc (SI unit: m).
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For Solar radiation see Solar Radiation for information about the options.
Angular Perturbations
If User-defined direction or Solar radiation is selected from the Incident ray direction vector list, you can include small perturbation factors designed to take the finite size of the sun (or another light source) into account. Select an option from the Corrections for finite source diameter list: None (the default), Create light cones at release points, or Sample from conical distribution.
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For None no perturbation to the initial ray direction is applied.
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For Create light cones at release points a cone-shaped distribution of rays is released at each point. Enter a value for the Number of rays in wave vector space (dimensionless) Nw (dimensionless). The default is 50. A cone-shaped distribution containing Nw rays is released at each point, which may cause a very large number of rays to be released.
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For Sample from conical distribution a single ray is released at each release point. This ray is given a random perturbation with uniform probability density within a cone-shaped distribution in wave vector space.
For Create light cones at release points and Sample from conical distribution, specify the Maximum disc angle Ψm (SI unit: rad). The default is 4.65 mrad, approximately the size of the solar disc when viewed from Earth.
For Create light cones at release points and Sample from conical distribution, select a Limb darkening model: None (the default), Empirical power law, Linear, or User defined. The limb darkening model reduces the intensity of solar radiation that is released from the periphery of the solar disk, relative to radiation that is released near the center. For Linear enter a Limb darkening coefficient β (dimensionless). The default value is 0.8. For User defined enter a Limb darkening coefficient fL (dimensionless). The default value is 1.
Select the Include surface roughness check box to include an additional perturbation term based on uncertainty in the orientation of the surface normal, which is common in imperfect reflecting surfaces. Enter a value or expression for the Surface slope error σ (SI unit: rad). The default is 1 mrad. The surface normal is then perturbed by a random angle, which is sampled from a Rayleigh distribution.
Incident Ray Intensity
This section is available when the ray intensity is solved for. Enter a value for the Incident ray intensity Ii (SI unit: W/m2). The default is 1000 W/m2.
Total Source Power
This section is available:
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when the ray intensity is solved for, and
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when Spherical, Hemispherical, or Conical is selected as the Ray direction vector.
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It is also available when the ray power is solved for, and then any choice of Ray direction vector displays this section.
Enter a Total source power Psrc (SI unit: W). The default is 1 W. In 2D, instead enter the Total source power per unit thickness Psrc (SI unit: W/m). The default is 1 W/m.
Illuminated Surface Theory
The following examples involve buildings or other objects being illuminated by solar radiation in a specific direction:
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Solar Dish Receiver: Application Library path Ray_Optics_Module/Solar_Radiation/solar_dish_receiver
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Vdara® Caustic Surface: Application Library path Ray_Optics_Module/Solar_Radiation/vdara_caustic_surface