Computing Capacitance
A capacitor, in its simplest form, is a two terminal electrical device that stores electric energy when a voltage difference is applied across the terminals. The stored electric energy is proportional to the applied voltage squared and is quantified by the capacitance of the device. This model introduces a model of a simple capacitor, the electric field and device capacitance are solved for ...
Voltage Induced in a Coil by a Moving Magnet
A magnet moving axially through the center of a coil will induce a voltage across the coil terminals. One practical application of this is in shaker flashlights, where the flashlight is vigorously shaken back and forth, causing a magnet to move through a multi-turn coil, which provides charge to the battery. In this model, the motion of a magnet through a coil is modeled, and the induced ...
Capillary Filling - Phase Field Method
This example studies a narrow vertical cylinder placed on top of a reservoir filled with water. Because of wall adhesion and surface tension at the air/water interface, water rises through the channel. Surface tension and wall adhesive forces are often used to transport fluid through microchannels in MEMS devices or to measure, transport and position small amounts of fluid using micropipettes. ...
Effective Diffusivity in Porous Materials
Transport through porous structures is usually treated using simplified homogeneous models with effective transport properties. This is in most cases a necessity, since the typical dimensions of the pores and particles making up the porous structure are several orders of magnitude smaller than the size of the domain that is to be modeled. This model introduces the concept of effective ...
Capacitive Pressure Sensor
A capacitive pressure sensor is simulated. This model shows how to simulate the response of the pressure sensor to an applied pressure, and also how to analyze the effects of packing induced stresses on the sensor performance.
Steady-State 2D Heat Transfer with Conduction
This example shows a 2D steady-state thermal analysis including convection to a prescribed external (ambient) temperature. It is given as a benchmarking example. The benchmark result for the target location is a temperature of 18.25 C. The COMSOL Multiphysics model, using a default mesh with 556 elements, gives a temperature of 18.28 C. Successive uniform refinements show a temperature of 18.26 ...
Buoyancy Flow of Free Fluids
This model couples the Navier Stokes equations and the heat transfer equations to examine density driven flow of free fluids. Here the fluid is in a square cavity with a heated wall. The buoyancy force is a Boussinesq term added to the Navier-Stokes equations. The equation is nondimensionalized, so the material coefficients are set up using Rayleigh and Prandtl numbers. The parametric solver ...
Frequency Selective Surface, Periodic Complementary Split Ring Resonator
Frequency selective surfaces (FSS) are periodic structures with a bandpass or a bandstop frequency response. This model shows that only signals around the center frequency can pass through the periodic complimentary split ring resonator layer.
Thin-Film Resistance
In modeling of transport by diffusion or conduction in thin layers, we often encounter large differences in dimensions of the different domains in a model. If the modeled structure is a so-called sandwich structure, we can replace the thinnest geometrical layers with a thin layer approximation, provided that the difference in thickness is very large. This method can be used in many ...
Pore-Scale Flow
This non-conventional model of porous media flow utilizes creeping (Stokes) flow in the interstices of a porous media. The model comes from the pore-scale flow experiments conducted by Arturo Keller, Maria Auset, and Sanya Sirivithayapakorn of the University of California, Santa Barbara. The geometry used in the model was produced by scanning electron microscope images. In this example, we take ...
