//www.denkrieger.com/community/exchange/ Receive updates on user-generated models in COMSOL Exchange Thu, 11 Jul 2024 21:14:06 +0000 //www.denkrieger.com/shared/images/logos/comsol_logo.gif //www.denkrieger.com/community/exchange/ //www.denkrieger.com/community/exchange/1022/ Transient absorption and Raman scattering measurements on noble metal nanoparticles offer complimentary information on their vibrational modes and mechanical interactions with their surroundings. We have built a COMSOL application for simulating both of these spectra for arbitrary nanoparticle geometry and different metal compositions. This multiphysics application uses the Solid Mechanics and Electromagnetic Wave modules, takes into account local changes in dielectric function for the metals, and can model the small vibrational amplitudes of real transient absorption measurements.

For more information on the method and to cite my model, consult:
Gelfand, Rachel, “Unified Finite-element Model for Transient Absorption and Raman Scattering of Vibrating Noble Metal Nanoparticles,”arXiv:2406.13067, June 2024.
Link: https://arxiv.org/abs/2406.13067 Thu, 11 Jul 2024 21:14:06 +0000 3.1720732446.1022 //www.denkrieger.com/community/exchange/883/ Micromagnetics Module has been updated to V2.02. Please note that the new module is not compatible with the mph files created by versions before V2.0.

The dynamics of magnetization in magnets are described by micromagnetic theory, governed by the Landu–Lifshitz–Gilbert equations. We built a customized "Micromagnetics Module" using the Physics Builder in the COMSOL Multiphysics® software, which can be used to perform micromagnetic simulations within the framework of the COMSOL® software. This Micromagnetics Module can be coupled straightforwardly to other add-on modules to perform multiphysics micromagnetic simulations, such as magneto-dipolar coupling, magnetoelastic coupling, magnet-thermal coupling, and more. The module package, along with a user’s guide, is available for download.

Questions and comments are encouraged to be left here.

Thu, 28 Mar 2024 05:22:14 +0000 3.1711603334.883 //www.denkrieger.com/community/exchange/992/ The behavior of the cryoprotective agents changes from liquid to solid during vitrification. In this model, I solved the coupled problem of heat transfer and fluid flow problem during cryopreservation, while considering surface tension. The results are in good agreement with the cryomacroscopy experiments.

This is a multi-physics model I developed in a small project in October 2019 to model large surface deformation and residual stresses during cryopreservation by vitrification.
To learn about cryopreservation: Bojic et al. Winter is coming: the future of cryopreservation. BMC Biol 19, 56 (2021).
To cite my model:
Guirguis, Rabin, "Modeling surface deformation in large-scale cryopreservation by vitrification," Cryobiology, 97 (264), December 2020. DOI: 10.1016/j.cryobiol.2020.10.064
Link: https://doi.org/10.1016/j.cryobiol.2020.10.064


Fri, 15 Mar 2024 21:31:18 +0000 3.1710538278.992 //www.denkrieger.com/community/exchange/1003/ Ultrasonic waves are generated by the piezoelectric effect to achieve the effect of acoustic heat Fri, 15 Mar 2024 15:56:12 +0000 3.1710518172.1003 //www.denkrieger.com/community/exchange/993/ The result of the time domain pulse signal passing through the narrow grating opening of the metal substrate. Wed, 13 Mar 2024 08:10:31 +0000 3.1710317431.993 //www.denkrieger.com/community/exchange/982/ We present a simple model of a Mobius loop waveguide, carrying RF in fundamental mode (TE10, rectangular) circulating endlessly around the loop. An animation is included. Enjoy. Tue, 19 Sep 2023 00:59:06 +0000 3.1695085146.982 //www.denkrieger.com/community/exchange/972/ First a definition of cleanup: remove the mesh builds, solutions, and compact the history of a COMSOL model file.

I have found that getting in the COMSOL GUI each time I need to clean up the mph model files is sometimes inconvenient. Therefore, I wrote a little bash script to do this from the command line using the COMSOL batch option. I have attached the script for general use by the COMSOL user community.

Happy cleaning !
Sat, 02 Sep 2023 01:59:09 +0000 3.1693619949.972 //www.denkrieger.com/community/exchange/971/ Formation is a fundamental physical characteristic of paper that can have profound effects on the production and performance of that paper. The finite element method can be utilized to better understand how formation affects mechanical quality control tests and their results. Using the Lorentzen & Wettre (L&W) bending resistance (15°) test, we investigate how paperboard formation affects bending resistance.

This model is used in the blog post "Paper Mechanics and the Benefits of Modeling Paperboard Formation" by Dr. Eric Linvill:

https://www.comsol.com/blogs/paper-mechanics-and-the-benefits-of-modeling-paperboard-formation/ Tue, 21 Mar 2023 08:41:40 +0000 3.1679388100.971 //www.denkrieger.com/community/exchange/961/ There are several ways to model multi-ply materials such as paperboard. Using a solid model with a thin domain for each layer is an obvious solution, but COMSOL also provides specific tools for modeling composite materials: the equivalent single layer (ESL) and layerwise theory (LWT) methods.

This model is used in the blog post "Modeling Multi-Ply Materials with Composite Materials Technology" by Dr. Eric Linvill:

https://www.comsol.com/blogs/modeling-multi-ply-materials-with-composite-materials-technology/ Tue, 21 Mar 2023 08:39:30 +0000 3.1679387970.961 //www.denkrieger.com/community/exchange/952/ Magnetoelectric materials hold untapped potential to revolutionize biomedical technologies. Sensing of biophysical processes in the brain is a particularly attractive application, with the prospect of using magnetoelectric nanoparticles (MENPs) as injectable agents for rapid brain-wide modulation and recording. Recent studies have demonstrated wireless brain stimulation in vivo using MENPs synthesized from cobalt ferrite (CFO) cores coated with piezoelectric barium titanate (BTO) shells. CFO–BTO core-shell MENPs have a relatively high magnetoelectric coefficient and have been proposed for direct magnetic particle imaging (MPI) of brain electrophysiology. However, the feasibility of acquiring such readouts has not been demonstrated or methodically quantified.

In order to evaluate the feasibility of using MENPs for recording neural activity, we created a custom COMSOL model for MENP response quantification. Our strain-based model is versatile and adaptable to different materials and geometries if material parameters are known. Our study, its results, and source files are open source and source files can be found here: https://github.com/ilhanbok/InSilicoNeuronalMENPs

Citation:

Bok I, Haber I, Qu X, Hai A. In silico assessment of electrophysiological neuronal recordings mediated by magnetoelectric nanoparticles. Sci Rep. 2022 May 19;12(1):8386. doi: 10.1038/s41598-022-12303-4. PMID: 35589877; PMCID: PMC9120189. Tue, 27 Sep 2022 15:20:16 +0000 3.1664292016.952 //www.denkrieger.com/community/exchange/841/ This archive provide the 2D and 3D models used in our paper

Nicolas Lebbe, Kim Pham and Agnès Maurel, "Stable GSTC formulation for Maxwell’s equations", IEEE Transactions on Antennas and Propagation ( Volume: 70, Issue: 8 )
DOI: https://doi.org/10.1109/TAP.2022.3161436
Preprint: https://hal.inria.fr/hal-03203013/document

These models implements in the frequency domain the enlarged version of the Generalized Sheet Transition Conditions (GSTC) used in electromagnetism to simulate the behaviour of thin periodic microstructures.
Mon, 19 Sep 2022 06:36:05 +0000 3.1663569365.841 //www.denkrieger.com/community/exchange/922/ The subject paper was presented at the 2020 COMSOL Virtual Boston Conference and received the best paper award. At that time, the author committed to releasing an application to reproduce the results shown in the paper and allow the users to experiment with the new stabilization method described. The author has also received many requests for this application. This exchange contribution provides the full model file (as opposed to an application), whereas, the reader/user will have full access to all the details described by the paper. Two model files are uploaded: (1) Burger's equation solver, and (2) shock tube solver. Of course, the user may change anything, but it is recommended to start with simple changes such as the number of elements, the element order (linear, quadratic, etc.), Reynolds number, or the selection of ideal/real gas in the shock tube model. The author and co-author have continued their collaboration, and are nearing publication of results for the 2D compressible flow extension to this new stabilization method. We look forward to sharing this new information with the COMSOL user and development community. Sat, 21 May 2022 19:04:53 +0000 3.1653159893.922 //www.denkrieger.com/community/exchange/893/ Circular dichroism is useful in chirality sensing. This archive provide the 3D models for calculating circular dichroism of plasmonic chiral structure. Sun, 16 Jan 2022 13:17:50 +0000 3.1642339070.893 //www.denkrieger.com/community/exchange/232/ In recent decade, the principle of bimetal bending was exploited in the field of thin films. Rolled-up micro- to nanotubes with multiple windings were obtained with this technology as well as wrinkled nanostructures. The competition of these two morphologies is studied by simulation of elastic relaxation with the help of Structural Mechanics Module. The structure consists of first layer compressed initially and second layer without initial strain. If the difference of the initial strains of the layers is sufficiently large, bending into the tube is preferred, otherwise wrinkling is observed. For medium strain gradient, intermixing shape of tube with wrinkles is the result of elastic relaxation. Additional information and qualitative experimental comparison can be found in article P. Cendula et al, Experimental realization of coexisting states of rolled-up and wrinkled nanomembranes by strain and etching control, Nanoscale 2014, 14326 - 14335, http://pubs.rsc.org/en/content/articlelanding/2014/nr/c4nr03986f Fri, 04 Dec 2020 13:26:02 +0000 3.1607088362.232 //www.denkrieger.com/community/exchange/513/ The interaction energies of colloids according to Classic DLVO based on the Derjaguin Approximation. The Classic DLVO consists of the non-retarded Attractive van der Waals interaction and the Repulsive electrostatic interaction energies. The equations are for a Sphere-Plate configuration and constant surface potential. The constant surface potential includes to models: one based on Hogg et al and other based on the Linear Superposition Approximation (LSA). It assumes an equivalent sphere for simplicity. The equations are broadly used in colloid science. Made in COMSOL 5.5.
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.
*Bhattacharjee, Subir, and Menachem Elimelech. "Surface element integration: a novel technique for evaluation of DLVO interaction between a particle and a flat plate." Journal of colloid and interface science 193, no. 2 (1997): 273-285.
*Gomez-Flores, Allan, Scott A. Bradford, Lei Wu, and Hyunjung Kim. "Interaction energies for hollow and solid cylinders: Role of aspect ratio and particle orientation." Colloids and Surfaces A: Physicochemical and Engineering Aspects 580 (2019): 123781. Tue, 01 Dec 2020 05:33:56 +0000 3.1606800836.513 //www.denkrieger.com/community/exchange/821/ The 4 models, with certainly perfectible Apps, are to illustrate the stress concentrations effects for structural interfaces.
They allow to adapt the discretisation and the mesh refinement, as well as the graph refinement.
Some more explanation in my COMSOL EU Conference 2020 poster.
I made these models, to check why COMSOL gives often smoother responses than classical FEM tools, following the excellent series of presentation of NAFEMS training guru Tony Abbey, for more see https://www.nafems.org and https://www.fetraining.net
Thu, 10 Sep 2020 09:09:52 +0000 3.1599728992.821 //www.denkrieger.com/community/exchange/721/ In this tool, we present a simple and robust numerical method able to predict, with high accuracy, the photo-thermal effects occurring for a gold nanoparticles arrangement under externally applied strain [1,2,3]. The physical system is numerically implemented in the COMSOL Multiphysics simulation platform. The gold nanoparticles distributions are excited by linearly polarized light. By considering the system at rest and under the action of a mechanical stress, we analyze the extinction cross section, and we observe the production of heat at the nanoscale. The purpose of this work is to describe how sensitive the local temperature of the gold nanoparticles arrangement is to the formation of localized photo-thermal hot spots.

[1] G. E. Lio, G. Palermo, R. Caputo, and A. De Luca, “Opto- mechanical control of flexible plasmonic materials,” Journal of Applied Physics 125, 082533 (2019).

[2] G. E. Lio, G. Palermo, A. De Luca, and R. Caputo, “Tensile control of the thermal flow in plasmonic heaters realized on flex- ible substrates,” The Journal of Chemical Physics 151, 244707 (2019).

[3] G. E. Lio, A. De Luca,C.P. Umeton, and R. Caputo, "Opto-mechanically induced thermoplasmonic response of unclonable flexible tags with hotspot fingerprint", Journal of Applied Physics 128, 093107, (2020). Sat, 05 Sep 2020 11:39:39 +0000 3.1599305979.721 //www.denkrieger.com/community/exchange/811/ These files of COMSOL and MATLAB make the calculation of the electromagnetic fields for a hexagonal array of Silicon hemispheres over a dielectric (mesoporous titania) array of cylinders with the same arrangement over a base layer of the dielectric on top a silica substrate.
The multipole decomposition of the particles is made and the surface energy and reflectance are calculated.

If you use this files, please, cite as
Molet, P., Gil-Herrera, L., Garcia-Pomar, J., Caselli, N., Blanco, Á., López, C., & Mihi, A. (2020).
Large area metasurfaces made with spherical silicon resonators, Nanophotonics, 9(4), 943-951.
doi: https://doi.org/10.1515/nanoph-2020-0035

Steps
1.Download the files from https://zenodo.org/record/4009029#.X00FljXtZhE (exceed the limit here)
2. Create a folder called C:\datacomsol\
3. Change the geometric and materials parameters if you want.
4. Run the COMSOL files (v.5.5) (_RF for Radiofrequency module or _WO for Wave optics module).
5. Clear all the tables in Tables.
6. Evaluate all the derived values.
7. Export all the data in Export.
8. run Matlab file (v.2010b). Mon, 31 Aug 2020 13:19:02 +0000 3.1598879942.811 //www.denkrieger.com/community/exchange/801/ This MATLAB tool extracts the losses of a litz wire winding from the field patterns.
The losses are computed in the frequency domain with Bessel functions.
The field patterns can be extracted with any simulation software (e.g. COMSOL, ANSYS, OpenFOAM).
The tool be used to compute the losses of different components, e.g., inductors, transformers, and chokes.

The method features several advantages:
* A reduced computational cost, since the discrete strands are not modeled
* The mesh can be coarse, independent of the skin depth
* Method valid up to several megahertz
* The litz wire can feature an arbitrary shape

The following limitations exist:
* The impact of the eddy current on the magnetic field is neglected
* The litz wire is composed of round strands
* The litz wire is ideal (insulated and perfectly twisted strands)
* The litz wire is defined with a fill factor, the exact position of the strands is not considered

The following field patterns are required:
* Integral of the square of the current density over the winding (for skin losses)
* Integral of the square of the magnetic field over the winding (for proximity losses)

This tool is developed by the Power Electronic Systems Laboratory at ETH Zurich and is available under the BSD License. The code is also available on the ETH Data Archive.

More information and latest version on:
https://github.com/ethz-pes/litz_wire_losses_fem_matlab Thu, 16 Jul 2020 15:21:46 +0000 3.1594912906.801 //www.denkrieger.com/community/exchange/791/ This COMSOL and MATLAB tool extracts homogenized material parameters for a litz wire.
This means that a complex litz wire, which is composed of many strands, can be replaced with a homogeneous material.
This virtual material parameters are defined such that the energy and losses matches the stranded litz wire.
More concretely, a virtual complex permeability and complex conductivity are extracted.

The method features several advantages:
* A reduced computational cost, since the discrete strands are not modeled
* The mesh can be coarse, independent of the skin depth
* Method valid up to several megahertz
* The litz wire can feature an arbitrary shape
* The impact of the eddy current on the magnetic field is considered

The following limitations exist:
* The litz wire is composed of round strands
* The litz wire is ideal (insulated and perfectly twisted strands)
* The litz wire is defined with a fill factor, the exact position of the strands is not considered

This tool is developed by the Power Electronic Systems Laboratory at ETH Zurich and is available under the BSD License. The code is also available on the ETH Data Archive.

More information and latest version on:
https://github.com/ethz-pes/litz_wire_homogenization_comsol_matlab Thu, 16 Jul 2020 15:19:59 +0000 3.1594912799.791

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