FEM Example Capacitance Two Balls/pl: Difference between revisions
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== Introduction == |
== Introduction == |
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This example is meant to show how to simulate the 6th example of [https://www.nic.funet.fi/pub/sci/physics/elmer/doc/ElmerTutorials.pdf Elmer GUI Tutorials], '''Electrostatic equation – Capacitance of two balls''', using the new [[FEM_Examples|FEM Examples]]. It illustrates how to setup the example, study it's various parts, solve it using the [[FEM_SolverElmer|Elmer Solver]] and |
This example is meant to show how to simulate the 6th example of [https://www.nic.funet.fi/pub/sci/physics/elmer/doc/ElmerTutorials.pdf Elmer GUI Tutorials], '''Electrostatic equation – Capacitance of two balls''', using the new [[FEM_Examples|FEM Examples]]. It illustrates how to setup the example, study it's various parts, solve it using the [[FEM_SolverElmer|Elmer Solver]] and visualize the results using [[FEM_PostFilterClipRegion|Clip Filter]]. |
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[[File:Two balls result 2.png|1200px]] |
[[File:Two balls result 2.png|1200px]] |
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<pre> |
<pre> |
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StatElecSolve: Capacitance matrix computation performed (i,j,C_ij) |
StatElecSolve: Capacitance matrix computation performed (i,j,C_ij) |
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StatElecSolve: 1 1 5. |
StatElecSolve: 1 1 5.07315E+21 |
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StatElecSolve: 1 2 1. |
StatElecSolve: 1 2 1.69428E+21 |
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StatElecSolve: 2 2 5. |
StatElecSolve: 2 2 5.07500E+21 |
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</pre> |
</pre> |
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* Here, our desired result is <code>C<sub>12</sub> = 1. |
* Here, our desired result is <code>C<sub>12</sub> = 1.69428</code>. This value is close to the {{incode|1.691}} given in the [https://www.nic.funet.fi/pub/sci/physics/elmer/doc/ElmerTutorials.pdf Elmer GUI Tutorials]. We can get an even closer value by making a finer [[FEM_MeshRegion|Mesh Region]] but this activity is left for the user. Also, the user is advised to play with the [[FEM_PostFilterClipRegion|Clip Filter]] to get a visual result similar to the first picture of this tutorial. |
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{{Tutorials navi{{#translation:}}}} |
{{Tutorials navi{{#translation:}}}} |
Revision as of 18:31, 19 March 2022
Tutorial |
Topic |
---|
Finite Element Analysis |
Level |
Beginner |
Time to complete |
Authors |
Sudhanshu Dubey |
FreeCAD version |
0.19 or above |
Example files |
See also |
None |
Introduction
This example is meant to show how to simulate the 6th example of Elmer GUI Tutorials, Electrostatic equation – Capacitance of two balls, using the new FEM Examples. It illustrates how to setup the example, study it's various parts, solve it using the Elmer Solver and visualize the results using Clip Filter.
Requirements
- A compatible version of FreeCAD designated in the tutorial overview.
- Use the Help → About FreeCAD to see the version of FreeCAD installed
- No external software is needed for loading the example, viewing the mesh and geometry as well as for visualizing the results.
- For solving the FEA, the solver software Elmer must be installed on your computer. See Elmer Solver for how to install Elmer.
Set up the example
Load FEM Workbench
- Start FreeCAD, the Start Workbench should be loaded
- Switch to FEM workbench.
Load the example
- Go to Utilities → Open FEM examples.
- When the GUI opens, find and open "Electrostatics Capacitance Two Balls". You can easily find the example in All or in Solvers → Elmer. For opening the example, either double click on it or select it and click Setup.
Understanding the Simulation Case
This case presents the solution of the capacitance of perfectly conducting balls in free space. A voltage difference between the balls results to electric charge being introduced to the system. The balls have also self-capacitance that comes from the voltage difference with the far field. Therefore a symmetric capacitance matrix with of size 2 × 2 needs to be solved. The capacitances may be computed from two different voltage configurations.
Understanding the Model
- The model contains three spheres.
- The two smaller ones are the perfectly conducting balls.
- The bigger one is to simulate the surrounding air.
- The two smaller spheres are fused together and then that fusion is is cut from the bigger sphere.
Analysis container and its objects
- Elmer solver
- Electrostatic equation
- a fluid material (to represent the surrounding air)
- electrostatic constraint (3 of them)
- File:Fem-thermomechanical-analysis.svgConstant Vaccum Permittivity
- a Gmsh FEM mesh
- Mesh region (for the smaller spheres)
Running the FEA
- In Tree view double click on the solver object .
- Click on Write file in the same task window. Watch the log window until it prints "write completed."
- Click on Run. Since this is a small analysis it should take a few seconds to run so wait till you see "ELMER SOLVER FINISHED AT" in the output.
- Click on Close in the task window after the run is finished.
- Two new result objects should be created, SolverElmerResult and SolverElmerOutput.
- If you get an error message on solver binary or similar when triggering the analysis check installation of Elmer Solver.
Visualizing Results
- Be sure the analysis is activated.
- Be sure the analysis still contains the result object, if not just re-run the solver.
- Make sure the mesh is invisible. If not, select the mesh object press Space to toggle the visibility.
- Double click on the SolverElmerResult to load in the task panel.
- Change the "Mode" to "Surface" and the "Field" to "potential". Press Ok.
- You will notice that the colour of the sphere has changed to blue and that the gradient on the right is showing values from 0 to +1. It should look something like this:
Post Processing the Result
- While we have successfully visualised the potential result, currently we are only seeing the zero potential in the air surrounding the two balls. To view the potential on the balls we need to apply a clip filter.
- In the tree view select the SolverElmerResult and then from the tool bar click on the Post Create Clip Filter.
- This will open the task panel with the clip filter configurations. Select "Plane" in the "Create" menu and check the "Cut Cells" box. After that click Apply.
- Then choose the same configurations (Surface and potential) as you have while visualising the results. Click Ok. Toggle the visibility of SolverElmerResult using Space and you should see something like this:
- Now we can clearly see that potential distribution in and around the balls.
Finding the Capacitance
- Our actual focus is to find the capacitance which is contained in the SolverElmerOutput.
- Double click on SolverElmerOutput to open it. Scroll down till you find:
StatElecSolve: Capacitance matrix computation performed (i,j,C_ij) StatElecSolve: 1 1 5.07315E+21 StatElecSolve: 1 2 1.69428E+21 StatElecSolve: 2 2 5.07500E+21
- Here, our desired result is
C12 = 1.69428
. This value is close to the1.691
given in the Elmer GUI Tutorials. We can get an even closer value by making a finer Mesh Region but this activity is left for the user. Also, the user is advised to play with the Clip Filter to get a visual result similar to the first picture of this tutorial.
- Materiał: Bryła, Ciecz, Nieliniowy materiał mechaniczny, Materiał zbrojony (beton), Edytor materiału
- Geometria elementu: Geometria elementu, Obrót w okół osi, Geometria elementu 2D, Element przepływu
Wiązania
- Elektromagnetyczne: Potencjał elektryczny, Gęstość prądu, Magnetyzacja
- Geometryczne: Obrót w płaszczyźnie, Zapis wyników z przekroju, Zdefiniuj odkształcenie
- Mechaniczne: Zdefiniuj przytwierdzenie, Zdefiniuj przemieszczenie, Zdefiniuj kontakt, Zdefiniuj powiązanie, Wiązanie sprężyny, Zdefiniuj siłę, Zdefiniuj obciążenie ciśnieniem, Zdefiniuj siłę odśrodkową, Zdefiniuj obciążenie ciężarem własnym
- Termiczne: Warunek początkowy temperatury, Zdefiniuj strumień ciepła, Zdefiniuj temperaturę, Zdefiniuj objętościowe źródło ciepła
- Zmieniające wiązania: Zdefiniuj przenikalność elektryczną próżni
- Siatki: Siatka Netgen, Siatka GMSH, Warstwa graniczna siatki, Obszar siatki, Grupa siatki, Utwórz zestaw węzłów, Siatka MES na obiekt środowiska Siatka
- Solver: Narzędzia CalculiX, Elmer, Mystran, Z88; Równania: Elastyczności, Elektrostatyczne, Siły elektrostatycznej, Magnetodynamiczne, RMagnetodynamiczne 2D, Przepływu, Strumienia, Ciepła; Solver: Kontrola pracy solvera, Uruchom solver
- Wyniki: Oczyszczanie z wyników, Prezentacja wyników; Postprocessing: Zastosuj zmiany, Prezentacja graficzna, Filtr rozpraszający, Skalarny filtr obcinający, Filtr odcięcia funkcji, Filtr odcięcia obszaru, Filtr konturów, Filtr danych wzdłuż linii, Wykres liniowości naprężeń, Filtr obcinania danych w punkcie, Utwórz funkcję, Filtr funkcji płaszczyzny, Filtr funkcji sfery, Filtr funkcji walca, Filtr funkcji prostopadłościanu
- Dodatkowe: Konfiguracja, Instalacja środowiska MES, Siatka, FEM Solver, CalculiX, Beton, Rodzaje elementów
- Jak zacząć
- Instalacja: Pobieranie programu, Windows, Linux, Mac, Dodatkowych komponentów, Docker, AppImage, Ubuntu Snap
- Podstawy: Informacje na temat FreeCAD, Interfejs użytkownika, Profil nawigacji myszką, Metody wyboru, Nazwa obiektu, Edytor ustawień, Środowiska pracy, Struktura dokumentu, Właściwości, Pomóż w rozwoju FreeCAD, Dotacje
- Pomoc: Poradniki, Wideo poradniki
- Środowiska pracy: Strona Startowa, Architektura, Assembly, CAM, Rysunek Roboczy, MES, Inspekcja, Siatka, OpenSCAD, Część, Projekt Części, Punkty, Inżynieria Wsteczna, Robot, Szkicownik, Arkusz Kalkulacyjny, Powierzchnia 3D, Rysunek Techniczny, Test Framework