# 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.

### Small Signal Analysis of a MOSFET

This model shows how to compute the AC characteristics of a MOSFET. Both the output conductance and the transconductance are computed as a function of the drain current.

### Capacitance Matrix of Two Spheres

This model compares the numerical and analytical solutions for the capacitance matrix of two nonconcentric spheres. It also illustrates the relation between the Maxwell capacitance matrix and the mutual capacitance matrix.

### Viscous Catenary

The catenary is the geometrical shape that corresponds to the curve followed by an idealized chain or cable supported at both ends and hanging under its own weight. The viscous catenary problem describes the motion of a cylinder of highly viscous fluid, supported at its ends as it flows under gravity. In the last decade this problem has generated significant theoretical and experimental interest ...

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 ...

### Dielectric Resonator Antenna

A dielectric resonator placed near a radiating element can be used to increase directivity and gain. Here, a block of quartz dielectric, with additional passive metallic antenna elements, is placed above a slot antenna. The fields in and around the antenna are solved for. The far field pattern and impedance is computed and improved performance is seen.

### Assembly with a Hinge Joint

This example illustrates how to model a barrel hinge connecting two solid objects in an assembly. In this model, the details of the connection are not the focus of the analysis, therefore, the hinge joint is modeled using a Joint feature in the Multibody Dynamics Module. The connected parts can be either rigid or flexible or a combination as shown in this model.

### Rotordynamic Analyses of a Crankshaft

See how to perform a vibration analysis of the crankshaft of a 3-cylinder reciprocating engine in this tutorial model. Due to the eccentricity of the crank-pin and balance masses on the crankshaft, it undergoes self-excited vibration under rotation. The crankshaft is modeled using solid elements to accurately capture the effects of the eccentricity of the crank-pin and balance masses. The ...

### Optimization of a Catalytic Microreactor

In this application, a solution is pumped through a catalytic bed where a solute species reacts as it gets in contact with the catalyst. The purpose of this example is to maximize the total reaction rate for a given total pressure difference across the bed by finding an optimal catalyst distribution. The distribution of the porous catalyst determines the total reaction rate in the bed. A large ...

### 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.

### Vibrating Micromirror with Viscous and Thermal Damping: Transient Behavior

Micromirrors are used in certain MEMS devices to control optic elements. This example model illustrates a mirror that is initially actuated for a short time and then exhibits damped vibrations. It simulates a vibrating micromirror surrounded by air and uses the *Thermoviscous Acoustics, Transient*, the *Shell*, and the *Pressure Acoustics, Transient* interfaces to model the fluid-solid ...

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