# 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.

### Homopolar Generator 3D

A homopolar generator is composed of an electrically conductive rotating disc placed in a uniform magnetic field that is perpendicular to the plane of rotation. The motion of the conductor through the static magnetic field induces Lorentz currents in the disc. By connecting the outside rim of the disc to the center via a stationary conductor, significant current can be generated. The flow of ...

### Magnetic Stiffness of an Axial Magnetic Bearing in 3D

The model illustrate the technique to calculate the magnetic stiffness in a 3D geometry of a permanent magnet axial magnetic bearing. The *Magnetic Fields* physics is used to model the bearing and compute the magnetic forces. The *Deformed Geometry* and *Sensitivity* physics are used to compute the magnetic stiffness. This model is featured and explained in much greater detail in the following ...

### Winding Designer for Electrical Machines

You can use this simulation app as a guide on how to automate selections using the Application Builder. In the example app, the selection algorithm depends on the relationship between the electrical and mechanical angles, which are generally used in the design of windings in electrical machines. Get more details in our blog post: [How to Automate Winding Design in Electrical Machines with an ...

### Iron Sphere in a 13.56 MHz Magnetic Field

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 ...

### Magnetic Prospecting of Ore Deposits

Magnetic prospecting is a geological exploration method that is applicable to certain types of iron ore deposits, in particular those made up of magnetite and hematite. The method consists of measuring the magnetic anomalies (changes in the earth's magnetic field) due to the presence of magnetic ores. The Magnetic Prospecting app simulates the effect of a deposit of magnetic ore on the earth's ...

### Thin Low Permittivity Gap Comparison

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.

### Axial Homopolar Induction Bearing in 3D

This model illustrates the working principle of an axial homopolar induction 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 axial ...

### Small-Signal Analysis of an Inductor

If an inductor's magnetic material is nonlinear, then the inductance depends on the current passing through it. This model consists of an inductor with a nonlinear magnetic core, where the small-signal inductance is simulated as a function of current. The model also investigates how the small-signal inductance depends on the DC current.

### Simulation of RF Tissue Ablation

This example exemplifies how to model tissue ablation through applying RF radiation. A more detailed description of the phenomenon, and the modeling process, can be seen in the blog post "[Study Radiofrequency Tissue Ablation Using Simulation](https://www.comsol.com/blogs/study-radiofrequency-tissue-ablation-using-simulation/)".

### Contact Impedance Comparison

The contact impedance boundary condition is meant to approximate a thin layer of material that impedes the flow of current normal to the boundary, but does not introduce any additional conduction path tangential to the boundary. This example compares the contact impedance boundary condition to a full-fidelity model and discusses the range of applicability of this boundary condition.

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