According to the manual, seems like Don Guido is suggesting to perform electrostatic calculations as a special case of thermal calculations.
To do that one should apply the analog relationships between electrical and thermal quantities.
Those are described in Table 13: Correspondence between the heat equation and the equation for electrostatics (metals and free space)
I’m working on that for a simple case with good results up to now but I’m missing some things.
To compute the Electric Field vector, Prepomax should be able to compute the Gradient of the Temperature Field (in fact – gradient )
I would like to request the possibility to add the Gradient of a Field as an Output to keep going.
Recently, support for electrostatic analyses with CalculiX was added to FreeCAD FEM. More types of EM simulations will follow but there are certain limitations. Elmer is way more capable in terms of EM and we have a new validated Joule heating example using that solver in FreeCAD.
I’m not sure. I guess in Pre-processor, so the different components are later available in results to perform additional operations.
I perform a Steady State thermal analysis. No electric field time variation is considered.
I find the Electric conductivity analogous thermal conductivity.
Electric potential V is analogous to the temperature field.
J (Current Density) is analogous to the Flux W/m2
Now I’m requesting -gradient (T) which is analogous to the electric Field E [V/m]
With the dot product of J and E we could obtain the Joule power density distribution (W/m3). Nodal values. Formula JxEx+JyEy+Jz*Ez.
That Power density field is directly the input for a Body Flux [W/m3] in a regular thermal analysis
Maybe Prepomax is not the most suitable for that kind of analisys. I see we would face another issue.
JxEx+JyEy+Jz*Ez ( W/m3) will give the Power density nodal values and in Prepomax Body Flux is based on Elements.
I know one can import a temperature field form a txt file but ¿Could we import a Power density field [W/m3] based on nodes too.?
I was just loking for workarrounds to a problem that shows up from time to time.
Here’s an example of electrostatic analysis based on Elmer GUI tutorial - two charges with opposite signs are defined and temperature corresponds to potential.
Nice!!.
If we had available the Gradient of T , we could see the Electric Field and could compute Heat Flux * Gradient(T) = Joule power density (W/m3) disipated inside the body.
Another example:
This is the Voltage drop inside a 2mm and 1mm lenght wire under a current of 20A. Directly computed inside Prepomax. For this simple case I can compute the Gradient of T and impose it to the same model beside as body flux to compute the thermal effect.
Final temperature at the surface is in excellent agreement with theory. (57.97ºC against Expected 58ºC) (I know It’s a very simple case but it shows prepomax could solve this problem with Steady State Thermal).
Fully done inside Prepomax. One can see the analogy of results. In one case (Left) it should be read as Voltage (0.0002V) and the second (Right) it is final surface temperature.
@FEAnalyst
Now it opens and I can see your spheres are in Air. Joule effect doesn’t have much sense here but the comments are valid anyway.
@belov Thanks for the theoretical framework abstract. I should have started there to make me more understandable. I’m not considering magnetic fields at all.
Yes, this was meant as regular electrostatics. I have another example for Joule heating (involving static current conduction) but it’s not working with CalculiX so far.
@belov
Is this problem stated at some book with their dimensions?
I can’t find it. Looks very interesting as its not much complex and it has analytical solution.
¿Could I take a look?. This Electro problems are new to me and would be nice to have more solved examples.
