COMSOL Exchange

A numerical ellipsometric analysis (NEA) of nanoscale layered systems

Fri, 06 Dec 2019 18:01:36 +0000

A simple and robust method able to predict, with high accuracy, the optical properties of single and multi- layer nanostructures is presented. The method exploits a COMSOL Multiphysics simulation platform and it
has been validated by three case studies with increasing numerical complexity: i) a single thin layer (20 nm) of Ag deposited on a glass substrate; ii) a metamaterial composed of ve bi-layers of Ag/ITO (Indium Tin Oxide), with a thickness of 20 nm each; iii) a system based on a three-materials unit cell (AZO/ITO/Ag), but without any thickness periodicity (AZO stands for Al2O3/Zinc Oxide). Numerical results have been compared with experimental data provided by real ellipsometric measurements performed on the above mentioned nanostructures ad-hoc fabricated[1]. The obtained agreement is excellent suggesting this research as a valid approach to design materials able to work in a broad spectrum range.

[1]G. E. Lio, G. Palermo, R. Caputo, and A. De Luca, \A compre-
hensive optical analysis of nanoscale structures: from thin lms to
asymmetric nanocavities," RSC Advances 9, 21429{21437 (2019).

ecore transformer changing node numbering

Mon, 30 Sep 2019 16:51:18 +0000

The e-core transformer model has been modified so that the node numbering in the circuit is different from the original. This means that the primary and secondary currents are now correct for the load resistor. There are still issues with this model and it needs a high voltage to generate a reasonable answer.

using a coil to measure emf of a field produced by a 3 core cable

Mon, 30 Sep 2019 16:50:15 +0000

This model is a 3D time varying FE model with a three phase balanced current in three conductors in a cable. There is a coil of wire which is measuring an induced emf from the field produced by the conductors. This model is related to a methodology in the following paper. M. Strickland, D. Strickland, A. Cross, B. Goss, M. Abedi-Varnosfaderani and T. West, "Low cost current measurement of three phase cables," 2018 53rd International Universities Power Engineering Conference (UPEC), Glasgow, 2018, pp. 1-6.
There is scope to make the system unbalanced as the conductor currents are implemented through circuit theory.

Microwave heating, drying and melting of dielectrics in radiating microwave chambers

Thu, 05 Sep 2019 14:53:30 +0000

The following models of microwave heat treatment processes of dielectrics in radiating type microwave chambers are presented:
1. Numerical modeling of the processes of melting dielectrics in microwave radiation type installations
2. Numerical modeling of microwave drying dielectrics processes with regulation of power source output power
3. Numerical modeling of microwave thermal treatment of large size dielectrics using continuous operation microwave installations

COMSOL Cell Relaxation model

Mon, 12 Aug 2019 11:54:28 +0000

Biological cells are essential for life as we know it. They not only store and replicate hereditary information in the form of DNA but also are instrumental in biological processes. In most, if not all, of these processes, the mechanical behavior of cells is a main factor in ensuring normal physiological functions.

On state estimation of all solid-state batteries (PDE solver)

Wed, 31 Jul 2019 00:38:44 +0000

This paper studies the state estimation of a solid-state battery modeled as a partial differential equation system. Three assumptions simplifying the battery model underlie the study of state estimation: (1) neglecting the generation/recombination of Li-ions in the solid electrolyte; (2) assuming the charge transfer number of 0.5; and (3) the uniform electrolyte concentration. Results of a sensitivity study show the validity of the approaches to model simplification for the voltage prediction. Especially, two simplified models focused on the diffusion dynamics at cathode only and at both cathode and electrolyte are used for state estimation by applying an extended Kalman filter (EKF). Simulation results show that the state-of-charge of the battery can be reasonably well estimated by the EKFs. However, the inaccuracy of the state estimation in low SOC range () due to weak observability cannot be addressed without including the diffusion dynamics in the electrolyte. This inclusion leads in a 40% reduction in state-of-charge estimation error, from 9% to 5% error for the considered case.

More details can be found:
https://www.sciencedirect.com/science/article/pii/S0013468619311661

Effective multipole expansion for scattering of particles on a highly conductive substrate

Mon, 24 Dec 2018 03:31:36 +0000

In this model, we simulate a light wave scatters off a silicon hemisphere on a PEC boundary and decompose the scattering to a set of 'effective multipoles' so that the scattering properties can be understood. This model is a simple extension of the multipole expansion model contributed by Grahn et al (https://www.comsol.com/model/multipole-analysis-of-electromagnetic-scattering-31901). It applies well to a class of problems, where the substrates, which the scattering particle is sitting on or elevated from, can be approximated as a perfect electric conductor. For example, substrates made of gold and silver in the mid-infrared frequencies.
A slight modification of this model can be used to describe scatterers on metallic substrates in the optical frequencies as well. In addition, it works on arbitrary background field, including oblique incidence of light. The derivation of the effective multipole coefficients and the result of this simulation is discussed in the following reference ('Generalized Method of Images and Reflective Color Generation from Ultrathin Multipole Resonators' by S.Q. Li et al, ACS Photonics, 2018. https://pubs.acs.org/doi/10.1021/acsphotonics.8b00161). It is applicable to design meta-atoms/nano-antennas for various applications.

How to Compute Radiating Near-Fields in Comsol Multiphysics via Stratton-Chu Aperture Integration

Fri, 14 Dec 2018 22:20:26 +0000

Note: This is a re-posting of previous work, accidentally deleted from the Model Exchange.
SUMMARY: The finite-element (FE)-based RF module in Comsol Multiphysics supports direct full-wave 3D computation of RF fields local to antennas and structures. It also provides computation of far-field patterns (via post-processing) via an included far-field formulation of the Stratton-Chu aperture integration method. However, there exist important cases where field points of interest are far enough away from antennas or other structures so as to make direct application of FE-based methods very cumbersome, yet not so far away as to ensure validity of alternative far-field approximations. In such cases, it is valuable to employ a Near-Field version of the Stratton-Chu method. This is a more general expression than the far-field-only version implemented by Comsol. We describe a way for users to implement this method themselves by defining certain new variables and component couplings. The essential expressions that we provide can be copied and pasted directly, for convenience.

"Saturation of Absorption with Carrier Kinetics" Tutorial Model for Webinar "Modeling Light-Matter Interactions for Photonics Applications"

Mon, 10 Dec 2018 15:56:41 +0000

A basic tutorial model for Webinar "Modeling Light-Matter Interactions for Photonics Applications". The Webinar was organized as a part of IEEE Spectrum Tech Insiders Series and sponsored by COMSOL.
The archived video can be watched here:
https://event.on24.com/wcc/r/1878151/DB32A11B5BB2D38949B94433E163AC2D

The "Saturation of Absorption with Carrier Kinetics" multiphysics model is built on the recent paper, Opt. Mater. Express 8, 3829-3834 (2018). Verification with alternative numerical methods has been performed by Shaimaa I. Azzam, Purdue University, USA.

Due to space limitations, the model does not include any solutions, but a typical runtime is short (~2 min). COMSOL ver. 5.4 (Wave Optics Module) is required.

"Reverse Saturable Absorption with Carrier Kinetics" Tutorial Model for Webinar "Modeling Light-Matter Interactions for Photonics Applications"

Mon, 10 Dec 2018 15:55:58 +0000

A basic tutorial model for Webinar "Modeling Light-Matter Interactions for Photonics Applications". The Webinar was organized as a part of IEEE Spectrum Tech Insiders Series and sponsored by COMSOL. The archived video can be watched here:
https://event.on24.com/wcc/r/1878151/DB32A11B5BB2D38949B94433E163AC2D

The "Reverse Saturable Absorption with Carrier Kinetics" multiphysics model is built on a recent paper, Nanophotonics, (2018), doi:10.1515/nanoph-2018-0139
Verification with alternative numerical methods has been performed by Shaimaa I. Azzam, Purdue University, USA.

Due to space limitations, the model does not include any solutions, but a typical runtime is not that long (~20 min). COMSOL ver. 5.4 (Wave Optics Module) is required.

2D Phononic Band Gap Model

Sat, 13 Oct 2018 17:43:31 +0000

The 2D phononic band gap model described in my Guest COMSOL Blog https://www.comsol.com/blogs/modeling-phononic-band-gap-materials-and-structures.

Tutorial files for COMSOL Webinar "Optical Antenna Optimization Using Genetic Algorithms"

Fri, 08 Jun 2018 12:57:38 +0000

The genetic algorithm (GA) optimization routine is directly applicable to a wide variety of physics and engineering problems, especially where the parameter space is large and the solution space has many extrema. In this webinar we demonstrated how to implement the GA routine in COMSOL Multiphysics, using the LiveLink for MATLAB module. We examined a multivalued objective function to identify the optimal geometry of an optical antenna--the "Omega particle"--such that it behaves as a Huygens source with maximal forward scattering and minimal backward scattering. Included are the MATLAB functions used to automatically build and solve each population of models, feed the results into a GA routine for evolution of the next generation, and monitor the process. The "LiveLink for MATLAB" module is required for use. "Webinar.m" is main script, with other supporting functions provided. "Webinar2.m" was used for showing a way to add more parameters ("genes") to the GA routine, adding the angle of the dipole arms of the particle. A model template is also included.

Excitation of plasmons in a sinusoidal grating

Sun, 13 May 2018 10:05:26 +0000

Simulation of plasmon excitation in a sinusoidal silver grating with a pitch of 750 nm for the first order of diffraction.

Simulation of surface acoustic wave sensors

Fri, 16 Feb 2018 21:09:11 +0000

SAW devices with a chemical-sensing overlayer provide for the selective sensing of particular gases. Sensing takes place due to electrical conductivity and mass density changes of the overlayer that change the propagation velocity of acoustic surface waves.

This model evaluates the change in eigenfrequency corresponding to a surface acoustic wave of a particular wavelength due to a conductive overlayer. The change in eigenfrequency is directly related to the change in velocity through c = f*lambda, where lambda is the wavelength.

Two models are attached. The first finds the eigenmodes corresponding to a surface wave propagating on a YZ-LiNbO3 substrate without a sensing layer. The second determines the effect of an overlayer of varying conductivity.

In this webinar, we will show how the COMSOL Multiphysics® software supports the design of SAW sensors by simulating the changes in the acoustic surface wave velocity due to changes in the overlayer. You will see a live demonstration of how to perform an eigenfrequency analysis of surface wave modes and derive the acoustic wave velocity, including how to specify model settings such as boundary conditions and material properties.

Surface Mounted Permanent Magnet Synchronous Machine

Fri, 16 Feb 2018 01:24:20 +0000

This model recreates the SM-PMSM published in [1]. The machine is random-wound; therefore slot conductors are represented in a homogenized way. An analytical model and test data for this machine are presented in [1]. The results are shown to match those obtained from the analytical model when saturation is ignored, and from test data when saturation is considered. The machine losses are presently ignored.

The Torque study obtains a torque waveform over rotation of one slot for a given current command, as calculated from flux linkages. The average torque produced may subsequently be obtained. It is noted that, being an overall machine energy-based evaluation (within FEA), this study is not expected to result in an accurate representation of torque ripple over the slot (which would require a significantly higher number of air-gap mesh elements, as well as convergence on the torque obtained from Maxwell Stress Tensor). It is, however, expected to provide an accurate value for average torque and flux linkages in the q- and d-axes.

Setting the current command to approximately zero and the Iron behavior to linear steel using "relative permeability", the average d-axis flux linkage due to the magnet is found to be in reasonable agreement with the analytical model results shown in Section IX of [1]. Setting the Iron behavior to nonlinear steel using "HB curve" results in an average d-axis flux linkage value in agreement with experimental data shown in Table II of [1].

The FluxLinkageMap study sweeps the current magnitude and angle, as well as rotor position over one slot. A flux linkage map is then obtained as a function of current magnitude and angle by averaging the values over one slot of rotor positions.

[1] B. N. Cassimere, S. D. Sudhoff, D. H. Sudhoff, "Analytical Design Model for Surface-Mounted Permanent-Magnet Synchronous Machines", IEEE Transactions on Energy Conversion, v. 24, no. 2, June 2009.

Conventional_Classic_DLVO

Tue, 21 Nov 2017 08:25:09 +0000

The interaction energies of colloids according to the Conventional Classic DLVO consists of the non-retarded Attractive van der Waals interaction and Repulsive electrostatic interaction energies. The equations are for a Sphere-Plate configuration and constant surface potential. This DLVO is called Conventional because the equations are obtained within the framework of the Derjaguin approximation assuming an equivalent sphere. The equations are broadly used in colloid science.
REFS:
*Elimelech, Menachem, John Gregory, and Xiadong Jia. Particle deposition and aggregation: measurement, modelling and simulation. Butterworth-Heinemann, 2013.
*Hogg, R. T. W. D. W., To Wo Healy, and D. W. Fuerstenau. "Mutual coagulation of colloidal dispersions." Transactions of the Faraday Society 62 (1966): 1638-1651.

3D microwave rotary heating

Mon, 25 Sep 2017 01:45:22 +0000

3D microwave rotary heating，This model is very interesting.Rotation for a long time, microwave heating simulation is a difficult problem, especially the three dimensional case is more difficult to calculate, this model using the ALE method implements the rotation of the microwave heating with microwave heating in the APP of improvement of cases, let a spinning heated objects present in front of you.

Simulations of Fish Swimming

Wed, 06 Sep 2017 07:12:46 +0000

We submit two different COMSOL5.2a models which simulate the swimming of a fish, specifically, the carangiform swimming in a virtual aquarium. The flexural motion of the fish is obtained by using a time-dependent field of distortions, meant to represent the action of fish muscles. Both models make use of both the moving mesh technique and the remeshing feature, and require about 10 Gb of RAM, and more than a day to run. The models are not yet solved (to avoid huge file upload), but are ready to run.

The principal differences between the two models are in the geometry and the activation law for the fish muscles. The model Fish_COMSOL_a.mph is more indicated for robotics applications and runs about for 30 hours, while simulation of Fish_COMSOL_b.mph is more indicated for biology studies and runs for about 50 hours.

It is possible to change the final time of simulation so to have shorter run times, or choose coarser mesh (Remark: fish swimming direction may change with a coarser mesh).

UPDATE: We uploaded the files using the new version of COMSOL. We also submit a new file: Fish_COMSOL53_a_light.mph with a coarser mesh to run faster simulations (computation time ~ 4 hours) but do not trust in the final result.

Further details in:

M. Curatolo, L. Teresi.
Modeling and Simulation of Fish Swimming with Active Muscles. Journal of Theoretical Biology, (2016).
Doi: 10.1016/j.jtbi.2016.08.025

https://www.comsol.com/blogs/studying-the-swimming-patterns-of-fish-with-simulation/

Surface plasmon polaritons by Kretschmann-Raether

Wed, 23 Aug 2017 15:40:19 +0000

Excitation of surface plasmon polaritions at the silver-air interface in Kretschmann-Raether configuration - Tutorial model for COMSOL/LFW webinar "Modeling Optoelectronic Devices and Plasmon Effects".

Surface plasmon polaritons by scattering

Wed, 23 Aug 2017 15:39:48 +0000

Excitation of surface plasmon polaritons at the silver-air interface by scattering configuration - Tutorial model for COMSOL/LFW webinar "Modeling Optoelectronic Devices and Plasmon Effects"