Operation "Mirror Blocks" defect
 

Hi,

today I tried to mirror some blocks but it didn't work out as I wanted it to ...
Some of the mirrored blocks edges do not fit as they should. (figure below)

How can I fix this problem. Later on I'll create O-grids around all inner cylinders and I would like to mirror them instead of creating O-grids at every 73 cylinder.

Another problem appeared when I "pre-meshed" the blocks - just for fun. (figure below)

Maybe there are some key-procedures I didn't do/ don't know. Or my strategy is bad. If someone knows a better strategy to block my geometry please tell me. I'd be happy to better understand this program. (geometry below)
It's a membrane reactor; a large cylinder with several small (membrane)cylinders inside plus in- and outlet.


Thanks in advance!

Sören

no need to create blocking for all small cylinders. just make the blocking for one single passage and rotate. there are of course other (maybe better or more efficient) ways to do the blocking. you've to try ;)

it would be helpful, if you can provide .blk and .tin files

Thanks for the hint Kai. For this model it is a good blocking-strategy - at least I, as an absolute beginner, think so. But the "Mirror Blocks" problem remains.
Later I want/must test two other models and compare them with my reference-model. For my other models (see attached figures) I might need the "mirror Blocks" option.
In one of my test-models I separate the large cylinder with circular plates, maybe 5-20 from bottom to top. In this model I'd like to mirror the blocks from one level down to the next.
.tin and .blk files of my reference model are attached. I can't attach the other models because ICEM imports the geometry incorrect from AutoCAD; Inner structure (helix and plates) is missing. And the autoCAD files are too big to attach.


Best regards

Sören

...ok, I just managed to create the .tin files from my two test-models...

first of all, before you start with your blocking, you have to prepare your geometry and define your parts (like inlet, outlet....).

second step is to think about the best blocking strategy. it makes no sense to start without that.

how does this reactor work? really don't understand. seems that there should be a closed volume, at least at the bottom!?

The functioning of the reactor is pretty simple. Inside there is e.g. water and in the small cylinders are hollow-fibre-membranes through which e.g. oxygen gases into the water without much turbulence like in other reactors. The inner "medium-large" cylinder is an auxiliary cylinder to support the global structure.
The inlet is the pipe at the bottom, outlet the one at the top.
So the fluid is streaming from the bottom to the top is being enriched with gas. The entire cylinder is supposed to be filled with the fluid. Membranes and inner cylinder are solid.
--> a .tin-file with the defined parts is attached.
--> closed volume is correct

Considering your suggestion for the blocking-strategy I would create a block around one of the outer small cylinder, construct an O-grid, delete the inner rectangular block, associate the inner rectangular edges to the small cylinder-curve, enhance the number of nodes, make the 4 remaining "O-grid-blocks" rotate. The same procedure for the other 3 rings of membranes. (see attached figure and attached .prj-file)

But now a problem appears:
how can I associate the blocks between the inner and outer circles to each other so that they fill the empty space?


Greetings

Sören

..................

...ok the answer was quite easy, I admit; "merge vertices".


Now my blocking has improved a little bit but isn't ready yet.
I tried to mesh (Pre-Mesh) it but it seems that an error or so appears. ICEM starts to work and collapses, meaning ICEM works and works and works... and nothing happens. I waited for about 15 Minutes.
Maybe the computer-power is too low or I created too many nodes. I don't know where the problem is. It would be nice if someone can tell me what I'm doing wrong.

attach blk

i'm stressed out at the moment, so far is your man :D

.blk - file is attached.

did you start from 2d blocking?`

No, I started with 3D-Blocking (3D Bounding Box to be exact).

this is really missing , you should work on this step first.

I am thinking to start with 2-D blocking and then I shall create the 3D using extrude face along the curve. Using same command I shall also create blocking for two pipes. At the end O-grid wherever deemed necessary.

energy382 more ideas are welcome. Lets start the competition and lets see who makes the best blocking. ;). I shall be sharing my ideas frequently.

I tried to mesh with auxiliary curves and also started with 2D Blocking. Constructing one circle of blocks was no problem but when I wanted to make another block with the option "create block -> initialize blocks" it didn't work. Two messages occurred (pictures below). When I click "no" nothing happens, when I click "yes" and "yes" my other blocks disappear and one new block appears.

2D-Blocking and extrusion seems to be an easy way but it's not working...???

Attached is also my last try to mesh the geometry. Maybe you can tell me if it will lead to a successful end or if it's just a waste of time...or if I could win the competition for best blocking...:)


Best regards and have a nice weekend!

tin and blk :http://www.4shared.com/zip/5RTz8E-C/3D-ME0M.html
This is the my rough working on model. Worked extensively on geometry and more work still needed to be done on this aspect. Helps in making blocking.

Right now I took 90 deg sector and created 2-d block. My idea is to covert it to 3d (fixed distance option) and then using the extrude along option to create blocking for two in and out pipes.

Regarding the 90 deg sector you have two options: either use periodic boundary condition and save computational cost, or you can copy the blocking for remaining 270 deg sector.

http://img197.imageshack.us/img197/4104/56767971.png
http://img404.imageshack.us/img404/5526/28288331.png
http://img20.imageshack.us/img20/7475/79461549.png
http://img35.imageshack.us/img35/630/30809186.png
http://img594.imageshack.us/img594/8535/61418506.png

Thank you very much for your help Far.

I can't have a look on your data right now because the computer-pool at university is only open during the week from 8-18 o'clock.
Your blocking looks to me more complex than I expected the work to be...but I'm still a beginner with ICEM..:)
Thanks for your advise and the time you spent on blocking.
I wish I could say that from now on I can work with ICEM on my own but I really doubt that...:(



Best Greetings

Sören

I will guide you at each step. The blocking is very simple. The blocking you think is complex is the magic of o-grid in ICEM, I have done nothing except pushing the o-grid button more often.

Meanwhile practice four to five hexa tutorials (Version 12) and also grid fin (to have flavour of bottom-up approach) http://mecanica.eafit.edu.co/~sorrego/icemtutorial.pdf

In next try created blocking for next set of circles. And also created buffer zone between them to uncouple the mesh distribution. But do not know why ICEM is not respecting the buffer zone and is forcing the unwanted mesh distribution.

Hi,
I do the tutorials you posted but it will surely take some time. The model looks good:) - I'll try to do one myself. I hope you are right and it's no magic :). If questions/problems appear, well I hope there won't be many...

Index control
 

I guess we should play with index control to make the appropriate edges parallel.

I didn't have the time to work out the details of the blocking (e.g. edge params, move verticies.....), but you can see my blocking in the attached pics (there may be even a better and easier way to create a blocking for this topology ---> time!!)

min. quality ~0,4 and min determinante 3x3 ~0,6 should be a good starting point to do some additional work on that blocking like moving nodes and smoothing (i prefer 10x ortho, 10x laplace and again 10x ortho, but that's your choice).

Hi,

@Far: The problem with the buffer-zone is due to the unequal distribution of nodes. On the outer side the node-distance under the circles is smaller than on the inner side (third of your pictures -> left side) because there is no circle oppositional to this one. So there are a lot of nodes on the outer side that need oppositional nodes on the inner side. They automatically choose the nearest ones on the inner side. This normalises only when on the inner side a bunch of nodes appear (third picture -> right side).
I think that is the reason for the odd-looking buffer-zone...?

@ Far: How did you create these round edges (picture) ?

I still have a problem with my 2D-Meshing. It is not possible to create a new 2D-Block by "Create Block>Create Block" without deleting the old Blocks? I have do copy the block, right?

My first blocking-try looked more or less similar to energy's try but I would like to comprehend how you, Far, created your Blocking.

I am trying to make a recording and then will upload on youtube. Wait one day.

I know this, but don't know how to control this in ICEM. I have created these type of grids in GAMBIT and Gridgen without any difficulty, but having difficulties in controlling these aspects in top down mesher (ICEM).

from blocing >>>>>>>edit edge >>>>> I use spline option (see Figure below)


I am creating one bigger block and then subtracting portion by portion to fit into the particular geometry part.


http://img191.imageshack.us/img191/4900/53598527.png

Here it is http://www.youtube.com/watch?v=roZNU...ature=youtu.be

Behind the scenes, all splits must propagate across mapped blocks... When you only split the visible blocking, we call those hidden splits "implied splits". Later, when you split across another index, it may simply expose those implied splits, or it may create a new split (with associated implied splits)... This becomes difficult to control.

For my own personal sanity, I would have split to capture the holes using full splits. Then I recycle as many splits as possible. A split across the block may be the left side of several holes, and then go thru between several holes and then be on the right side a the next ring... But at least all the splits are radial.

I am not clear what you mean by a buffer zone... You could create a buffer zone by deleting a block "permanently". If you don't delete permanently, then the mesh still carries across the structured VORFN blocks. Another way to break the propagation is to change the block type from structured to "Free"... The paved blocks do not force propagation across them.

Oh, you might just want "Linked Bunching". Look into the help to see exactly how to use this (found under Edge Params), but it will let you match distributions across indices where you have differing numbers of edges...

I tried it, but it is not working. smaller edges on one side are directly linked to larger edges on the other side, therefore linked bunching is not working. It is also strange all edges have some parallel edges on other side, remaining edges (since for more circles I have more edges) have no corresponding edge on other side and therefore their meshing converge to single node on the buffer zone.


Like this?

http://img804.imageshack.us/img804/1087/22093927.png

Hi,

first of all, a thank-you for your help, energy, Far and PSYMN.
I did a quite O.K. - well I would say so - blocking myself. There are still some "minor" problems remaining and the way I chose isn't the most efficient one. I hope you know why some of the problems appeared, how to solve the and maybe you can give me some feedback about my blocking-strategy.

I encircled the critical regions in the attached picture - I tried to vary the number of nodes but in these regions it didn't work? And there is also a curiosity with the middle circle.


@Far: In your video you created 2 O-Grids. The outer one you used for your splines. Did you make this to express the boundary layer around the membranes?


Mistakes in the blocking-strategy:
1. For each ring I generated a new block from my initial 2D-Block with "Transform
Blocks >> Translate Block". Then I split the block in 15 blocks to fit in the
ring-segments.
For the next ring I repeated this process.
==> in this case the adjacent blocks in neighboring rings aren't connected, right?
They are only connected within the ring.
--> a better way is to use one block, split it vertical and horizontal to not lose the
connection across the rings. (like you did Far?)
2. Is it recommendable to draw the edges through the rings (pic-2) so that in every ring
will be the same amount of blocks or could for example three blocks end on one
block (pic-1)?


Kind regards

good.

I had no idea about the important flow areas, so just created the one o-block to capture the boundary layer around the pipes. Interior O-block was created with the intention to improve the mesh quality as well as to capture the flow (if any).

Yes, otherwise you will have problems of disconnected blocks. As ICEM is top-down approach, so one should come from the bigger one which fits the whole geometry to be meshed.

This should not be the problem if mesh is looking nice. I feel that you have some association problems in outer most blocks.

Topology can be improved further (alteast 10 times ;)). Lets work on it.

Topology-improvement at least 10 times...I expected more :D

Ok, set the goal to 50 times and lets start the race.

I'll try to complete an improved version tomorrow. Today I have only 10 minutes left till the computer-pool closes...

Thanks for the quick answer, Far!

Some problems and 3d blocking
 

Here are some problem areas which can be rectified easily (further splits)

http://img840.imageshack.us/img840/3...lemsmarked.jpg

Once 2-D topology is perfect then we shall move towards 3-D blocking.

right, the area at the right down corner should be solid.

and I didn't use part mesh setup to set the number of nodes...so this maybe explains some differences in the regions.