COMSOL仿真经验记录

什么是电磁学？

电磁学属于工程领域。传统上，人们通常通过分属于不同子领域（例如静电学或光学）的专业术语和实验设备逐步认识电磁学。例如，在静电问题中常见的设备包括电容器，而在光学系统中常见的器件包括光纤。这些设备在形式和功能上差异较大，但从理论层面看，它们的物理行为基本都可以由麦克斯韦方程组进行统一描述。

在工程应用中，麦克斯韦方程组通常需要结合其他物理定律共同使用。这些补充关系用于描述电磁场与材料介质之间的相互作用，例如介电响应、磁化效应以及能量传输等过程。

以下介绍仿真过程中常见设置及其对应项的含义，持续更新中……

常见边界条件设置

散射边界条件设置（Scattering Boundary）

The scattering boundary can be used to scatter rays in reflection and transmission from any boundary using one of several scattering models.

• Diffuse scattering will scatter rays according to Lambert’s cosine law. That is, the probability of a ray propagating in a given direction within a solid angle dω is given by cos θ dω where θ is the angle between the direction of the ray and the wall normal.
• Isotropic scattering will cause rays to be randomly scattered in all directions.
• Surface slope error will cause the surface normal to be perturbed by a random angle sampled from a Rayleigh distribution based on the value or expression for the Surface slope error σ (SI unit: rad). The default is 1 mrad.

Rays can be released from a Scattering Boundary in both reflection and transmission. The available options include Reflected and transmitted (default), Reflected, or Transmitted.

If both reflected and transmitted rays are selected, then unless total internal reflection occurs, the primary rays are expected to be transmitted.

Wavelength or Frequency Reinitialization

This section is available when the distribution of released rays is either Polychromatic (specify vacuum wavelength) or Polychromatic (specify frequency). When activated, the wavelength or frequency of a ray can be reset as it interacts with the selected boundaries.

The wavelength or frequency distribution function can be defined as:

• None – the wavelength or frequency is set to a user-defined expression.
• Normal – the wavelength or frequency follows a Gaussian distribution with mean μ and standard deviation σ.
• Lognormal – the wavelength or frequency follows a lognormal distribution with mean μ and standard deviation σ.
• Uniform – the wavelength or frequency is randomly drawn from an interval defined by λ0,min and λ0,max (or νmin and νmax).