# 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.

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 ...

### 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.

### Sub-Component Lumping in Acoustics Using the Impedance Boundary Condition

This application illustrates a modeling approach for deriving physically consistent simplified models in the Acoustics Module. The approach consists of converting complex sub-components to an impedance boundary condition and otherwise using simple acoustics throughout the COMSOL model. As a consequence, significant computational speed-up can be achieved. The example treated here consists of a ...

### 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 ...

### 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.

### Absorptive Muffler with Shells

This model describes the pressure wave propagation in a muffler for an internal combustion engine. The purpose of the model is to show how to analyze both inductive and resistive damping in pressure acoustics as well as coupling the fluid to the surrounding elastic shell structure of the muffler. Finally, the eigenmodes of a pure structural problem is analyzed and the modes compared to peaks ...

### 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 ...

### 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 ...

### Operational Amplifier with Capacitive Load

An operational amplifier (op-amp) is a differential voltage amplifier with a wide range of applications in analog electronics. This tutorial models an op-amp connected to a feedback loop and a capacitive load. The op-amp is modeled as an equivalent linear subcircuit in the *Electrical Circuit* interface, where it is inserted into an outer circuit. The model is partially based on the SPICE ...

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