Effective Nonlinear Magnetic Constitutive Relations for Frequency Domain Studies
COMSOL Multiphysics version 5.2 includes support for effective magnetic constitutive relations in the form of effective HB or BH curves. This functionality can be used to model nonlinear magnetic materials, such as saturable metals in a frequency domain study, by approximating them with an effective inhomogeneous linear material. You can use the formulation to compute the approximate (first-order harmonic) response of a nonlinear material subject to time-harmonic excitation, avoiding the computational cost of a full transient analysis.
A comparison of the solution obtained with a Time Dependent study (blue), the solution obtained with a Frequency Domain study using a linearized material (green), and the new effective material approximation (red).
New App: Effective Nonlinear Magnetic Curves Calculator
The Effective Nonlinear Magnetic Curves Calculator application is a companion to the new Effective Nonlinear Constitutive Relations functionality. Magnetic-based interfaces in the AC/DC Module support the Effective HB/BH Curve material model that can be used to approximate the behavior of a nonlinear magnetic material in a frequency domain simulation without the additional computational cost of a full transient simulation.
The Effective HB/BH Curve material model requires the effective Heff(B) or Beff(H) relations defined as interpolation functions. This utility app can be used to compute the interpolation data starting from the material’s H(B) or B(H) relations.
The interpolation data for the H(B) or B(H) relations can be imported from a text file or entered in a table. The app will then compute the interpolation data for the Heff(B) or Beff(H) relations using two different energy methods. The resulting effective material properties can be exported as a COMSOL Material Library file and further used in a model with the Magnetic Fields interface of the COMSOL Multiphysics software.
The user interface of the Effective Nonlinear Magnetic Curves Calculator app, showing the interpolation data and plots for the BH curve and the computed effective curves.
External Nonlinear Magnetic Materials
The Magnetic Fields physics interface in the AC/DC Module, and the corresponding 2D interfaces in the core COMSOL Multiphysics software, can now use external material models implemented as user-defined dynamic libraries. This increases the flexibility and the modeling capabilities of the physics interfaces. This functionality is built into the External Material feature and allows the user to define custom advanced material models, such as hysteresis models, state-dependent models, or even models using a different discretization scheme.
New App: Touchscreen Simulator
Intended as a tool for early proof of concept in capacitive touchscreen device development, the Touchscreen Simulator app evaluates a simulated capacitance matrix as well as the electric field norm.
The app computes the capacitance matrix of a touchscreen in the presence of a human finger phantom, where the position and orientation of the finger are controlled via input parameters. This includes electrode unit cell array size, the finger location, angle and touch level, the substrate and superstrate thicknesses and their material properties.
The user interface of the Touchscreen Simulator app, with a 10x10 electrode array touchscreen model and dB-scaled electric field plot.
New App: Magnetic Prospecting
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 magnetic field and predicts the measured anomaly at specified measuring points on the surface. You can import heightmap images or digital elevation model (DEM) files to define the orography of the region as well as the geomagnetic field data for the specified location.
The computation generates a plot of the magnetic field on the earth's surface as well as numerical data of the expected anomaly at specified measurement locations in the region.
The Magnetic Prospecting app's user interface provides inputs to specify the geomagnetic field and magnetic properties of the ore.
New App: Induction Heating of a Steel Billet
Induction heating is a method used to heat metals for forging and other applications. Compared with more traditional heating methods, such as gas or electric furnaces, induction heating delivers heating power directly to the piece in a more controlled way and allows for a faster processing time.
The Induction Heating of a Steel Billet application can be used to design a simple induction heating system for a steel billet, consisting of one or more electromagnetic coils through which the billet is moved at a constant velocity. The coils are energized with alternating currents and induce eddy currents in the metallic billet, generating heat due to Joule heating. The billet cross section; the coil number, placement, and size; as well as the initial and ambient temperature and the individual coil currents can all be specified as inputs in the app.
After the solution has been computed, the app plots the billet temperature and current density during the processing. Furthermore, it computes numerical data on the expected temperature ranges in the billet and the power balance of the system.
The Induction Heating of a Steel Billet application computes the temperature range in the billet and the power balances, and shows electric current density and temperature plots as results.
Smith Plots: A Conventional Way to Present Matching Properties
A new Smith plot group allows you to plot impedance, admittance, and reflection data in a Smith grid. Smith plots are useful for relating complex-valued S-parameters (reflection coefficients) to input impedance, admittance of antennas, transmission lines, or other network components. For studies where an S-parameter plot is generated by default, a Smith plot is automatically generated.
Smith plot of the CPW bandpass filter where the color scale indicates the simulation frequency, showing that the filter is matched to 50 Ohm around 7.65 GHz.