Ray Optics Module Updates

For users of the Ray Optics Module, COMSOL Multiphysics® version 6.1 provides a new feature for computing fluence rates, improved pseudorandom number generation (PRNG), and additional materials in the Optical material library. Read about these updates and more below.

Fluence Rate Calculation

Fluence rate is defined as the amount of radiation that would hit a small spherical detector at any location in the simulation domain, divided by the cross-sectional area of such a detector. A new domain accumulator feature, Fluence Rate Calculation, is now available for computing fluence rate. This feature is valuable when simulating ultraviolet (UV) purification systems because it can be used to predict the amount of UV radiation that bacteria and other pathogens will absorb when passing by a source of UV radiation.

You can see this new feature in the new Annular Ultraviolet Reactor and Annular Ultraviolet Reactor with Particle Tracing tutorial models.

A UV lamp model showing the fluence rate in the Magma color table and rays shown with red arrows.
Slice plot of the fluence rate surrounding a UV lamp. A small fraction of rays is also shown.

Improved Pseudorandom Number Generation

The Ray Optics Module includes a variety of functionality that relies on PRNG, such as:

  • Monte Carlo modeling of light extinction in particle-laden media
  • Diffuse and isotropic scattering
  • Surface normal perturbations for modeling rough boundaries
  • Conditional ray–boundary interactions

The PRNG methods used in these examples have been improved and are less likely to incur correlations between random numbers that should ideally be uncorrelated. This includes random boundary conditions acting on different rays as well as unwanted correlations between randomly generated vector components. The existing Solar Dish Receiver tutorial model demonstrates this new improvement.

A parabolic dish model showing the reflected rays in the Magma color table.
Reflected rays from a parabolic dish, including the effects of solar limb darkening and surface roughness. The roughness model applies a pseudorandomly generated perturbation to the surface normal direction when initializing the direction of each released ray.

Option to Store Only Accumulated Variables in Solution

Depending on your application, the accumulated variables (such as the deposited ray power or fluence rate within a domain) may be more valuable information than the position and direction of individual rays. You now have the option to retain only the accumulated variables in the solution while discarding the degrees of freedom associated with the rays, which reduces file size. You can see this feature in the new Annular Ultraviolet Reactor and Annular Ultraviolet Reactor with Particle Tracing tutorial models.

The COMSOL Multiphysics UI showing the Model Builder with the Geometrical Optics node highlighted, the corresponding Settings window, and a reactor model in the Graphics window.
Settings for the Geometrical Optics interface when only the fluence rate is stored in the solution (not the individual ray positions) to reduce file size.

Optical Material Library Updates

In the Optical material library, available in the Ray Optics Module and Wave Optics Module, the fused silica and i-line glasses from Ohara Corporation have been added. Compared to other types of glass, fused silica and i-line glasses generally have greater transmittance at ultraviolet and near-UV wavelengths.

New Tutorial Models

COMSOL Multiphysics® version 6.1 brings three new tutorial models to the Ray Optics Module.