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Comments
ps; you shouldn't need to use any ccx commands. other than forcing pardiso if you want to use that solver. it should default to pastix. if you turn mixed precision off it is more reliable.
The center hole is not really a bug. ND need a special treatment when there are some elements on the axis of rotation. I know because it happens the same when I apply (-y,x,0) BC. If X and Y are =0 the normals are ill conditioned.
I have had an insight about your comment:
"it just repeated each blade individually, instead of them being all in one mode, like it should be".
Be sure to add the perturbation parameter for the contacts to keep working the whole analysis.
I'll bet you a beer that you're watching this
Ideally this should be done in the phase of model preparation. It requires to leave the model 0.1º-0.2º short .
Once the step is meshed, that small section that is short can be fulfilled with a slice of the same size build with revolve from the opposite side.
Then the slice is relocated and bonded to the model.
Internal is not multithreaded so I don’t really think this is needed but Anthony commented about having issues with this point.
Tested.
the last thing i wanted to try was too big to solve with 16gb.
Created a slice of the left face with revolve (1 element per thickness), disconnect slice elements, reposition that slice with rotation on the opposite side, bond and the model is ready for Cyclic Symmetry.
i redid the fan model, to make it smaller, so that i could solve it the way i wanted. once i did that, the results of the full rotor make a lot more sense. so some of the tricks:
model one sector in cad, then mesh that sector in netgen. use the element quality plot to make sure you have a good mesh.
import the mesh into mecway and use the rotate mesh command to make the full rotor
then use bonded contact, to join all the sectors together, as the nodes will be way off at the seams (thanks to @disla for this idea)
lastly, i did a nonlinear prestressed modal with complex freq analysis using ccx
the best way i can find to solve the full rotor is use the (number of modes you want * the blade count). in this case (6 * 7 = 42).
now, when you get the results back, there will be results for all of the nodal diameters. however, they will be sorted from lowest to highest freq only. cyc sym sorts from low to highest, for each nodal diameter. the full rotor will be all mixed up basically.
the last remaining oddity is you will get a random amount of phase shifted duplicate modes. they seem to occur for the higher nodal diameters. on this version of the fan model, i had 18 of those. the interesting thing is i solved for 42 modes. if you subtract out the random modes, you get the 24 modes from the cyc sym analysis.
so it's still a pain to do a whole rotor. however, the above method helps a lot. previously, i was truly getting unexplained modes. i think the main culprit was netgen. however, doing the complex freq analysis should help some too.
if you want the updated models, let me know.
Please share your latest models. Did you run them with paradise solver? I’m still unable to run Pardiso. Have tried other options posted per Victor, still no luck.
i took the old link down to save online storage space. i updated all of the files except for the solve time spreadsheet.
one thing that occurred to me with model size issues is it looks like around 700k nodes will work for any analysis with 16gb of memory. so if you had a full rotor if it's less than 700k you should be fine. an easy way to figure the cyc sym limit is to just divide 700k/# sectors. so that should be your mesh size target for one sector. i think if you output all sectors it will probably still work. it gets a lot slower outputting all sectors, but i think this might keep it from going out of core. my ssd is about 11x less bandwidth than most peoples. my memory is about 3x less bandwidth. so as soon as it hits out of core, it's game over for my laptop. victor has also said you need a patch to get that running for ccx pardiso. however, even if i patched the software it wouldn't help the laptop any. also, the smaller the node count, the more likely you are to be able to animate the mode shapes. i usually can't do that. i can output a video of them though. so that's good.
ps;
the limits i mention are for pardiso. i think pastix is easier on memory. so you may be able to solve a larger model with pastix. although, mecway still needs a lot of memory to output all sectors. my formula takes mecway into account also. the formula is just from my experience on my laptop. so you might find you can use a slightly different formula.
%programfiles%/Mecway/Mecway19/ccx/ccx_win64_mkl_pardiso_source_2.19.zip