# 案例集锦

COMSOL Multiphysics 案例库模型来自广泛的应用领域，包括电气、机械、流体和化工等行业。您可以下载现成即可使用的模型，以及详细的建模步骤说明，作为您建模工作的起点。请使用“快速搜索”查找与您的专业领域相关的模型，并登录或创建一个与有效的 COMSOL 许可证相关联的 COMSOL Access 帐户，下载模型文件。

### Electrodynamic Bearing 3D - new

This model illustrates the working principle of a passive electrodynamic bearing. An electrically conducting rotor rotating in a magnetic field produced by a permanent magnets induces eddy currents on the conducting rotor. The eddy currents, in turn, produce a magnetic field that opposes the magnetic fields by the magnets and induces a force that opposes the motion of the rotor. The radial ...

### Capacitive Micromotor

This tutorial shows how to model a 2D capacitive micromotor. The motor consists of a rotor and a stator made of polysilicon. The cogs of the stator are subjected to a time-varying pulsed voltage such that the voltage on adjacent cogs vary by a phase difference of 2p/3. As a result, a time-varying torque acts on the rotor thereby rotating it about its center. This model shows how to use an ...

### Thin Low Permittivity Gap Comparison - new

The thin low permittivity gap boundary condition is meant to approximate a thin layer of material with low relative permittivity compared to its surroundings. This boundary condition is available for electrostatic field modeling. This example compares the thin low permittivity gap boundary condition to a full-fidelity model and discusses the range of applicability of this boundary condition.

### Cold Crucible - new

A cold crucible is used for the manufacturing of alloys that require a high degree of purity, like titanium alloys for the aeronautic industry. The cold crucible in this model is made of several water-cooled copper sectors that form the container in which the alloy is manufactured. The harmonic current flowing in the coils will induce a current in the crucible flowing in the opposite ...

### Quadrupole Mass Filter - new

A quadrupole mass filter (QMF) is a key component of a modern mass spectrometer. A QMF uses direct current (DC) and alternating current (AC) electric fields to analyze positive or negative ions by mass to charge ratio. A QMF consists of 4 parallel rods spaced equidistantly, the ratio of the rod radius to the radius of the inscribed circle is 1.148. Opposite pairs of rods are electrically ...

### Electric Shielding Comparison - new

The electric shielding boundary condition is meant to approximate a thin layer of highly conductive material that provides an additional current path tangential to a boundary. This example compares the electric shielding boundary condition to a full-fidelity model and discusses the range of applicability of this boundary condition.

### Iron Sphere in a 20 kHz Magnetic Field - new

An iron sphere is exposed to a spatially uniform, sinusoidally time-varying, background magnetic field. The frequency of the field is such that there skin depth is smaller than the sphere radius. The induced currents in the sphere and the perturbation to the background field are computed. Proper meshing of domains with significant skin effect is addressed.

### Iron Sphere in a 13.56 MHz Magnetic Field - new

An iron sphere is exposed to a spatially uniform, sinusoidally time-varying, background magnetic field. The frequency of the field is so high that the skin depth in the sphere is much smaller than the radius. At such high frequencies it is possible to model only the fields and induced currents on the surface of the sphere, thus avoiding the need for solving for the fields within the volume of the ...

### Multipactor - new

Multipaction can occur when electrons are accelerated by a high frequency RF field into surfaces. Secondary electron emission can occur and under the right conditions there can be an exponential growth in the number of electrons. The multipaction effect is strongest at a specific RF frequency, which depends on the dimensions of the device and the applied voltage.\n\nThis model requires the ...

### Capacitance in a Microstrip

To illustrate how to calculate lumped parameters of capacitance, this model calculates such in a microstrip. The example shows the two different ways of calculating this: with a static analysis and with a time-harmonic analysis.