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Capacitor above Ground -- System is not convergent.
Posted Mar 13, 2012, 7:41 a.m. EDT Low-Frequency Electromagnetics, Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.2a 0 Replies
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I'm struggling to get a convergent solution for the following problem:
I'm trying to model an geoelectric system (which aims to measure the resistivity of the ground) using 4 capacitive coupled sensors, having a square shape. Two sensors are used as a source dipole (with a high conductivity), at which a certain current is applied. The two remaining ones are thought to be coupled to a voltmeter, hence have infinite resistivity. In Comsol I'm using the AC/DC module with the electric currents equation set in frequency domain. The other boundaries of the model are electrical insulated, source points are at the one node of each of the source sensors (as explained further down).
The model is thought to check against an analytical solution over a homogeneous halfspace, hence the model consists of two blocks (20 m*20 m*20 m & 20 m*20 m*10 m) representing ground and air, respectively. The sensors are placed 0.001 m above ground, since they are thought to the be capacitively coupled to the ground.
I think this is the first problem, this small gap between lower surface of the sensor and ground compared to the overall model size has to be fine meshed. However, I'm not so firm how to show the mesh properly so that I'm able to check whether it is meshed sufficiently or not.
The other point where I'm not sure about is the input of the current into the system. Right now, I'm modeling it by applying a Point Current Source onto one node of each of the source sensor, one positive at the other one negative to get a dipole. Since the sensor is highly conductive, this should charge the whole sensor domain.
However, my main problem is, that the solution is not converging. I think it has something to do with the model discretization rather than the physics I applied. But I would appreciate it if someone could give me some hints how to check the mesh properly, and if the modeling of the physics like I did it is correct or if there is another way of doing it.
Sorry about the long text, but I thought it might help to understand my problem. Attached you will also find the model I set up.
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Hello Sebastian Uhlemann
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