Discussion Forum

For me the best part is that the comsol 4 code is rewritten from scratch, unlike 3.X versions. I have a lot of problems with ALE formulation due to being added to femlab later, etc.

Also, you don't have to redo everything several times. You can have different mesh cases, plots, ... and activate them when you want. No need to redo everything each time or use script.

Hi

I have spent quite some time on V4 betas, I really like it, and in fact I noticed already at the confeence in October last year, that after 2x1hour presentation of the principles, you catch up very quickly (apart the solver part but it was not fully finished at that time).
I'm getting old I believe, and I'm rather critical to all changes, but this time I have become entousiastic (0%-- for MS vista and office 2007, 100%++ for comsol V4) so I agree COMSOL has done a great job.

But there are certainly some "small" things such as CNTRL Z and CNTRL C / V that have to be improved, that will come with the time, just thinking of the effort to rewrite everything, I'm impressed.

I expect my official V4 in a few days, I'm getting impatient ;)
Have fun Comsoling
Ivar

I've been fighting with 4.0 for the last 2-3 days and am having a tough time.

Documentation/help seems to be the most troublesome. For example, today I am trying to find out how to impose strong constraints. Typing in the "strong constraint" in search box on the right pulls up 0 hits on local help and 1 hit on Comsol support knowledge base. So I click on that and somewhat surprised that the "hit" it found says "your search did not match any documents". Not infrequently, when I highlight something (e.g "Continuity 1") and ask for dynamic help then I get "Use the model builder..."

Searching user guide is a bit better, e.g., on p502 where it says it is as easy to do strong constraints as weak constraints. Great!! On p 501 it says: for weak constraints, right click on main interface feature (available in all physics interfaces). So far I've opened six or seven different physics examples and right clicked every button I can find on each of them. The word "weak constraint" sure doesn't show up. Maybe its a probe or a pair or something - I haven't explored those yet.

And then on thermal/fluid coupling, I've learnt from comsol-support that the wall transfer functions are not implemented yet, so will need to be typed in by hand. Hopefully not as weak constraints....

So anyway, I'm sure I'll get it all sorted out sooner or later. But I would not, at all, say that the help file is the most useful part of it. Sooner or later I'm sure there will be some advanced 4.0 tutorials online and/or some 4.0 models posted. But the next few weeks are going to be a bit rough....

Regards, John

Aha!! Stumbled upon: Options -> Preferences -> Model builder

Click on "Show More Options" and, for good measure "Show equation view". Weak and strong constraints show up!!

Now at least I have a box to type in constraints. Sadly, attempting to use my linear extrusion gives me an error message. I try highlighting "Pointwise Constraint 1" and click "Dynamic Help"... Nope.... Help message is the usual "Use the Model Builder window to".... Sigh

At least I can see the equations again. Regards, John

p.s. More progress:: found this: www.comsol.com/support/knowledgebase/1064/

Hi

I can only confirm, do not uninstall 3.5a yet, but after a few days with 4 you will probably not want to go back again, at least I felt that way while fighting on the beta. Im still waiting for my 4; it's due one of these days, getting impatient.

One of the changes are the "h" in the weak constraints has dissapeared, and replaced by direct equations, so the functionality is stillé ther. Once I managed to get the equatrions to show up As John said above the learning curve increased it's slope as you can see how its done inside Comsol, and then by comparing to 3.5 you catch the essential.

THe operators were a bit confusing to begin with, but there too I found it a questopn of havints, I was still missing a few such as the rms deformation, but OK if it is not added, I'll write it out in two steps

Have fun Comsoling
Ivar

This is like pulling teeth...

The trial license I got on Friday has expired. It says on it in big letters "Expiration data May 15, 2010"

Apparently that is not true. COMSOL 4.0 will no longer start, complains about a license error, and if I try "repair" from the CD and do "Check license" it says, yup, the license has expired.

So much for having a productive weekend..... :-(

Hello John and David,
there are some issues with the dynamic help feature. It has been fixed together with some other bugs in a 4.0 hotfix that we will post to the COMSOL website hopefully tomorrow. I will drop a note in this forum when it is available. In the mean time, you can work around most of the help issues by following these instructions:
www.comsol.com/support/knowledgebase/1064/

You probably have a time limited pre-press trial license from a workshop. Please contact your local COMSOL representative to get a permanent license.

Niklas Rom, COMSOL

This is like pulling teeth...

The trial license I got on Friday has expired. It says on it in big letters "Expiration data May 15, 2010"

Apparently that is not true. COMSOL 4.0 will no longer start, complains about a license error, and if I try "repair" from the CD and do "Check license" it says, yup, the license has expired.

So much for having a productive weekend..... :-(

Good morning to everybody,

I have a huge problem, I've been fighting with comsol fro 4 days and I cannot solve my problem, for sure someone else is bettere than me sicne that I am novice on it. I have to siomulate magnetic field with multi turn coil of a iron bar rounde by coil haveing the same axis of bar.

can You help me?

How can I do a 3D multi-turn coil with comsol, can someone send me some pdf document of exercise?

Thanks

Hi

well multiturn coils is tricky, the easiest is often to consider the coil as a single item, and define a

current_density = N * Iwire / coil_section

where N is the number of turns, and Iwire the wire current and Section tot total coil section

At least start like that, then once this works (do not forget enough Air around to allow the magnetic field to loop around, and check the examples in the model library)

Later you might try the "multi turn coil" BC if that exist in V4.0 (Do not foret that v4.0 was the first releas of the new system, if possible try to use a more recent version)

To make things behave quicker, you could start in 2D-axi then model until your are hapy with the results, and foinally try aq full 3D model, if you have plenty of RAM

--
Good luck
Ivar