Joule heating

DaveStupple

Trying some initial simulations to model heating in a resistive filament. I have tried with solid hex elements, but the resistor option is not available. Tried with line elements (both with and without finite section thickness), I gave them a resistance, I get potential and current solutions, but adding power density to the solution gives a red entry in the tree: Compatible with element types and materials: unknown. What am I missing? Thanks.

Victor

Power density in the solution is currently only available for solid and shell elements. You should be able to extrude the line mesh into a single element wide strip of narrow shells.

DaveStupple

Works fine now. I was confused that the resistor button was not available, but I just used the conductivity property. Applied this to a trivial problem of filament temperatures, mainly because I wanted to see if I could make the helical mesh. It would be a nice touch if I could adapt the theory for two parallel plates radiating to each other, so that I can approximate the effects of adjacent coils heating each other. I don't think it would change much, but I haven't done the sums.

prop_design

what did you mesh that with

barmin

That kind of mesh can be obtained by Salome for example

prop_design

thanks I'll have to give it a try. does it do automatic hex dominant meshing

Victor

CCX has the capability of modelling radiation between surfaces. Last I checked, it was a bit complicated to set up by hand so it's something I want to add to the UI eventually. It could be that you have to copy the generate *RADIATE keyword block and add the CAVITY parameter.

DaveStupple

Thanks Victor, I'll take a look at the dreaded CCX manual.

Prop design, I know not much about Salome. I have it installed and have had a go, but I found it quite confusing. I believe it does do hex dominant. It looks like a useful tool.

These lovely helical meshes were done in Mecway 11, and were pretty straightforward. I'll try to remember what I did. To create the helix I used >Mesh tools >Create >Curve generator >Cirlce. Enter two equal radii for the overall diameter of the helix, then OK, which will return you to the Curve generator window with the parametric equations to generate a circle. Change the Final p entry from 2*pi to, for example, 20*pi to give 10 turns, then in the Z box enter some small value *p to move the helix along the z axis, such as 0.003*p. Increase the Number of elements figure to give a sufficiently smooth curve. Hit OK and you should have your helix made of line elements (subject to a bit of tweaking of the figures). Next >Mesh tools >Create >Plate mesh and enter the radius of the wire, and -if you like- adjust the meshing parameters (with a live preview, I think). This gives you the cross section of the wire. I moved this cross-section so that its centre was on the end of the helix, then rotated so that it was oriented normal to the end of the helix. Merge the two nodes at the centre with the Merge nodes tool. Next use the sweep tool: for the profile select your cross section, and for the path select the helix (I had these as named selections to make this easier). Hit OK and you should have have your helix. I think you can avoid having to move the cross-section to the helix by linking the helix end node and plate centre node with a line element, but you will have to delete the elements that the line elements create as they sweep.

I think this should work, but if I have misremembered let me know and I will work through it. Pretty impressive built-in meshing tools, I think.

MartinB

In reply to an earlier post, Salome Meca is great for modelling and making hex dominant (or tet) meshes. Look for code-aster-windows if on windows..Export as UNV to continue in Mecway, or try your hand with the code aster solver (not for the faint of heart
But I'm impressed you've meshed this with Mecway!

prop_design

Thanks guys. Prior to your replies I tried Salome. I also tried gmsh again. I have tried that several times and I just can't stand it. Salome was equally terrible. The windows download is ridiculously huge. It takes up a lot of hard drive space once it finally unzips and the gui was awful. So I promptly deleted it. I prefer Netgen and Mecway. But it would be nice to have auto hex meshing. Cool that you made that model in Mecway. It's a nice looking model.

Sergio

Even if Salome use Netgen, there are some tools not available on Netgen or Mecway for meshing. I agree that takes several steps to acomplish a simple task that could be done easily on a comercial program, but there is nothing better in the open source world. In my case I use a lot for extructured hexa meshes, combined with Mecway to made the extrusions/revolutions or create groups.

tk1537

I have also used Salome to create hex meshes on STEP solids, then import the mesh into Mecway for contraining and solving with good results. You have to fiddle a lot with settings, partitions, 2D and 1D mesh controls (for 3D) and submeshes for regions, but nice hex meshing is possible. Gmsh is saying that they plan to incorporate Hextreme into v5.0 when released, which is supposed to produce 1 step solid hex meshing. We'll see.

prop_design

I can't figure out the Gmsh interface. I would love auto-hex meshing though. That would make it worth trying to learn.