# 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.

### Electric Shielding Comparison

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.

### Relativistic Diverging Electron Beam

When modeling the propagation of charged particle beams at high currents and relativistic speeds, the space charge and beam current create significant electric and magnetic forces that tend to expand and focus the beam, respectively. The *Charged Particle Tracing* interface uses an iterative procedure, in this example, to efficiently compute the strongly coupled particle trajectories and ...

### Characteristic Parameters of a Coaxial Cable

Electrical cables, also called transmission lines, are used everywhere in the modern world to transmit both power and data. These cables carry electromagnetic energy, but instead of dealing with the full complexity of the electromagnetic fields, they are more commonly classified according to parameters such as capacitance, inductance, and impedance. In this model of a coaxial cable, we ...

### Gecko Foot

In nature, geckos use dry adhesion forces to climb walls. They have inspired researchers to develop synthetic gecko foot hairs to be used in, for example, robot applications. This model contains the nano/micro hierarchy of a synthetic gecko foot hair, where cantilever beams both in nano and micro scales describe the seta and spatula parts of one spatula stalk attached to a gecko foot. The ...

### Rotating Channel

A lab-on-a-chip platform can be realized on a rotating disc by designing channels and other features to use the Coriolis or centrifugal forces to manipulate the flow. These forces are controlled by changing the angular velocity of the disc, so the platform is programmed by using a controlled sequence of angular velocities. In a microchannel, the centrifugal force induces a parabolic flow profile ...

### Mixed Diffuse-Specular Radiation Benchmark

This model shows how to use the Mathematical Particle Tracing interface to simulate mixed diffuse-specular reflection between surfaces in an enclosure. This model is separated in two parts. The first part compares the heat fluxes computed by the Mathematical Particle Tracing interface with the exact solution for two identical infinitely long parallel grey plates under mixed diffuse-specular ...

### Simulating the Motion of a Bicycle on a Flat Surface

This model demonstrates the motion of a bicycle with a hands-free rider when given an initial forward velocity and perturbed with a lean about the forward axis. This is implemented through the Multibody Dynamics module in COMSOL. The wheels of the bicycle have been modelled assuming knife-edge contact with the ground and pure rolling constraints have been implemented. Stability analysis was ...

### 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 ...

### 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 ...

### Disc Resonator Anchor Losses

This model shows how to compute the anchor loss limited quality factor of a diamond disc resonator. The resonator is anchored to the substrate by a polysilicon post and power is transmitted to the substrate through the post. A perfectly matched layer is used to represent the essentially infinite substrate. The model is based on a paper presented at the 2007 COMSOL conference in Grenoble: P. ...

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