# Application Gallery

The Application Gallery features COMSOL Multiphysics® tutorial and demo app files pertinent to the electrical, structural, acoustics, fluid, heat, and chemical disciplines. You can use these examples as a starting point for your own simulation work by downloading the tutorial model or demo app file and its accompanying instructions.

Search for tutorials and apps relevant to your area of expertise via the Quick Search feature. To download the MPH-files, log in or create a COMSOL Access account that is associated with a valid COMSOL license. Note that many of the examples featured here can also be accessed via the Application Libraries that are built into the COMSOL Multiphysics® software and available from the File menu.

### Electrodynamic Bearing

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 ...

### Electric Impedance Sensor

Electric impedance measurements are used for imaging and detection. Applications range from nondestructive testing and geophysical imaging to medical imaging. Several alternative techniques are shown to model such a system. One of them shows how to use conditional expressions to define spatially dependent material properties. Another shows how to use multiple terminals for distributed sensing ...

### Electromagnetic Plunger with Stopper

This is a transient model of an electromagnetic plunger with stopper restricting the linear motion. The model consists of a magnetic core, nonmagnetic guider, multi-turn coil, nonmagnetic stopper/blocker, and magnetic plunger attached to the spring and damper at the far end. The electromagnetic force on the plunger due to the transient current in the coil is calculated using the Maxwell stress ...

### Topology Optimization of a Magnetic Circuit

This model presents an example of topology optimization of the magnetic circuit of a loudspeaker driver. Using topology optimization, we are able to find the shape of a nonlinear iron yoke in order to maximize its performance and, at the same time, minimize the weight such that it is smaller than the original design.

### Iron Sphere in a 20 kHz Magnetic Field

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.

### Effective Nonlinear Magnetic Curves Calculator

The Effective Nonlinear Magnetic Curves Calculator application is a companion to the *Effective Nonlinear Constitutive Relations* functionality. Magnetic-based interfaces in the AC/DC Module support the Effective HB/BH Curve material model that can be used to approximate the behavior of a nonlinear magnetic material in a frequency domain simulation without the additional computational cost of a ...

### Tubular Permanent Magnet Generator

This tutorial shows how to model the tubular permanent magnet generator in 2D axisymmetry. The generator consists of a modular stationary stator and moving/oscillating slider. The stator is made of three-phase multiturn windings and an iron core. The slider is made of permanent magnets and iron spacers. The open circuit voltage in the three-phase stator windings due to the periodic motion of the ...

### Computing the Effect of Fringing Fields on Capacitance

A typical capacitor is composed of two conductive objects with a dielectric in between them. A voltage difference applied between these objects results in an electric field between them. This electric field exists not just directly between the conductive objects, but extends some distance away, this is known as a fringing field. To accurately predict the capacitance of a capacitor, the domain ...