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Wing Woes. Difficult geometry,(or inept user) Swept and tapered 3d wing
Hey all,
I have been trying to mesh a 3D wing in ICEM using diamonddx's youtube vid as a guide http://www.youtube.com/watch?v=T0XpZpmOG_g I must not have wrapped my head around ICEM as much as I thought because I am still having difficulty getting it to mesh at all (let alone actually get a good quality mesh) Here is the general wing layout http://img51.imageshack.us/img51/1428/06wing.png This pic is the side view (looking from the outside). You can see something weird seems to be happening there. http://img708.imageshack.us/img708/9...chedtowall.png The blocking strategy around the wing http://img594.imageshack.us/img594/8...alblocking.png Im not quite sure if im on the right track, but need to fix a couple of things or if I should scrap it and start from scratch. Does anyone have any thoughts? I have attached my files below for anyone to have a look at if they are interested. https://www.dropbox.com/s/tetojb7p2o...%20%283%29.zip Geometry files https://www.dropbox.com/s/ja1xc8vf29...r_geometry.zip And some more pictures too https://www.dropbox.com/s/jbf1u8jctp..._size_pics.zip Edit: Latest files https://www.dropbox.com/s/c972geny1f...oa_mach5_5.zip |
I should note that the wingtip is modeled as a *small aerofoil section (see pic). It doesn't taper down all the way. I did this for 2 reasons, the first being I wasn't entirely sure how to get it to taper cleanly in Proe and secondly, I thought having the edges would help with letting me associate stuff to the tip.
http://img849.imageshack.us/img849/2796/09wingtip.png Also note, the mesh is very rough as I have been just trying to get it to work. I had planned on refining later on. |
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Alright I got mesh to behave a lot nicer. But I still feel that it is of questionable quality(even when I refine it). So Im not sure if anyone has any thoughts on my mesh.
http://img197.imageshack.us/img197/485/completemesh.png For anyone else looking into this, all I did was follow the method in the youtube vid all the way to the end. Then I did the following to get it to start playing nice. 1. Deleted all blocks that were sitting inside the wing (pic1) should be 11 blocks to delete 2. Create iso curves (pic2) 3. Associated the corresponding curves to edges (pic3) As simple as that. (I hate when I problem is simple but it still takes you ages to figure out lol) |
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Hi Stuart. Sometimes I have the same error. Look at the picture. This time diamondx told me I should prove "Associate Face to Surface" tool. I say you this because I´ve seen your second pic. Try to do that in this area.
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You got it :)
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Does anyone know how I can make the mesh around the leading edge more square so it all flows together nicely? Or is it always going to do that because of the way its blocked?
http://img197.imageshack.us/img197/9...aroundwing.png I am trying to keep the mesh smooth and keep the elements orientated correctly with respect to the flow but Im starting to thing that this blocking strategy was the wrong approach. How should I go about tidying up that blocking? Any tips or hints. Latest files too. https://www.dropbox.com/s/oaha2s05mr...er_mach2_1.zip |
Stuart (2),
Great work so far, although I am slightly worried what happens at your wingtip. My advice (contrary to diamonds excellent tutorial. Sorry mate!) would be to wrap the O-Grid around the wing tip rather than propagating it to the extent of the domain. Good Luck, Stu |
Hey Stu...well I guess you are Stu(1) seeing as you got in first :p
I absolutely agree with you, ive been staring at all those blocks for ages trying to figure out what to do with them. So far I have made it to this stage http://img197.imageshack.us/img197/485/completemesh.png Im not sure the best way to show you the tip, but investigating it....it kinda looks acceptable. But it wouldnt be a surprise in the slightest if it is completely rubbish and I just havent found a way to look at it. http://img5.imageshack.us/img5/5181/tipblocking.png Ive been staring at this block mayhem for hours now trying to work out something better. Unfortunatly this is only the second thing I have tried meshing in ICEM so far, and I still havent figured out how the blocking actually works yet haha. http://img594.imageshack.us/img594/8...alblocking.png If you have any ideas on how to salvage that...or if neccecary I could start from scratch (less preferred, but I want to do it right to be honest.) Here are my latest files anyways if you want a look. Be nice though, im still very...uhh special, when it comes to ICEM. haha https://www.dropbox.com/s/ald6fjw3dz...%20%282%29.zip |
Stuart23: I agree with your idea about o-grid around wing instead of taking it into the farfield. That approach is well suited to flat tips with almost same order of chord length at tip. :D
Stuart: I am afraid, you will have to go back and make the new geometry without tip airfoil. sorry for home work ;) :p You have sharp TE, collapse blocks behind TE. PS: Now we have two Stuarts, hoping Stuart junior shall be as good as Stuart Senior. :) I will take a look on files ... |
I'll revisit my model see if I cant tidy that edge up, but if I do end up doing that way, is there a guide or something I can use? Im still pretty useless atm ( I may not have the skills of Stu Senior but I have perseverance. I dont like to be beaten by a program :p :D I would do well in the Tron universe. hehe)
But as it stands I wouldn't know where to start with that approach..I'll do a bit of googling though and see what I can come up with. Hopefully I find something useful. I'm running short on time for this one though, so if I cant get it solved soon (*verry soon) I will have to abandon it for now otherwise the rest of the project will go down the drain as well. If I do figure it out, ill make up a guide for full on beginners seeing as wings seem to be a pretty popular....On that note, I have come across little guides that people done here and there. Perhaps the best of these should become stickies (or put in their own section) so people can find them easily. Just a thought. |
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Ill keep tabs on them. At the moment Im flat out getting trying to get this done, but soon as I get a breather I will try to find and collate some of the stuff (that way I can do it properly).
For now though, I cant figure out how to wrap an Ogrid around the tip like so the blocks dont propagating through the whole domain. I kind of dont get how you could actually do that, as how do all the small complicated blocks around the wing connect to a big simple block sitting next to it? (unless of course I am misunderstanding what you mean...which is quite likely haha) I dont suppose anyone would want to knock up a tutorial quickly on it :D ...its one of those tutorials that would be helpful to heaps of people (I cant find any tutorials on 3D swept and tapered wings) Or at least point me in the right direction.... I'm pretty stuck and running out of time. Any help would be immensely appreciated. Plus I plan to give back to the cfd-online community too, so that can only be a good thing :D |
These are the ICEM CFD files for DLR F6 for DPW2 and probably done by The Simon. Wonderful blocking.
https://dl.dropboxusercontent.com/u/68746918/DPW2.zip PS: At the moment I am recording tut on turbomachinery meshing. The purpose is to make the mesh (Full Hexa) from simple CAD model and within 30 minutes. I have in mind the tut on this geometry as well. http://imageshack.us/a/img844/7038/dlrf62.jpg http://imageshack.us/a/img812/7585/dlrf6.png http://imageshack.us/a/img191/3323/dlrf62001.jpg |
That is a seriously nice mesh. That blocking is great, its more or less what I had pictured in my mind, but I just cant figure out how to execute it.
Im going to see if I can copy the way he has done it.....not holding my breath though. Is it possible to do what he has done but with a sharp trailing edge and curved leading and trailing edges? |
blockings of wing can be approached in many ways... that blocking was not great i should remove that video. instead i follow simon's 2d version , and apply it to a 3d geometry...
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Ali :
Your blocking around the wing resembles to the Simon's blocking. The main problem is how to handle the 3d wind with finite thickness (wing tip blocking). |
i will project everything til the far field
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Hi diamondx, I agree with FAR that your blocking is not that bad for 3D wings that are a straight extrude but for wings are swept and tapered the blocking around the tip needs more work to keep it clean.
Even if you could still use similar blocking but then transition to a big block (like in the DLR F6 FAR posted earlier) it would be a lot cleaner and you wouldnt be getting any weirdly orientated or sized elements in the farfield region. Its obviously doable, but Im just not sure how to go about it. |
Just found out I have bigger problems then just my tip blocking.
This the pressure contour at about 1 back from the wing http://img191.imageshack.us/img191/8463/screwedmesh.png This is the front view of a swirling strength isosurface plot (wing is middle of right hand size) http://img694.imageshack.us/img694/8...icityfront.png Top view of swirling strength isosurface plot http://img713.imageshack.us/img713/5...rticitytop.png Not sure whats going on there but that simulation was with this mesh https://www.dropbox.com/s/tetojb7p2o...%20%283%29.zip (SST with gamma-theta transitional turbulence) If I cant get this sorted out within the next day or so Im going to have to abandon it. |
Go to o-grid tab and select all blocks inside the wing and click on apply. You will get o-grid around the wing.
Edit: Don't look at the results at the moment, they may be misleading. Only concentrate on good mesh and getting good convergence. |
I already did an o-grid around this wing (like in the vid)? Plus I have deleted the blocks inside the wing.
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When you select the blocks inside the wind for o-grid generation, do not select any face.
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I will give that a go, but I am still trying to figure out why I got those weird results I mention earlier.
There is nothing i this area so i figure it has to be an artifact of the mesh. And its in one of the big blocks in the farfield, I would have been less surprised if it had happened where there was heaps of blocks (inline with the wing but towards the wall opposite the one the wing is attatched too) So yeah, im real confused. |
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At the moment you task should be to get a good mesh. Even after getting numbers I do not look on flow field unless necessary to find reason for some change in data set. |
I did monitor my cl and cd and while they were roughly in the region I expected them they were not converging as nicely (werent particularly stable)
But the reason I pointed that out, is that there is something wrong with my mesh in the region I thought was good quality. Its almost like there is some solid object or something in that region (looking at streamlines shows them moving around "something"). So im not sure if there are some solid elements that I generated in my mesh by accident or something So I agree with you completely, Im just trying to figure out why the mesh quality is poor in those areas. |
wrong mesh in one area may give you problem area in other region as numerical error is accumulating (numerical diffusion etc) due to wrong calculation of flux, thats why I saying do not monitor flow field at the moment. It does not mean you never look on flow field ;).
Once your mesh is good, most of the problems will go away, believe me :). Just put hard work on mesh, as it is the first step to successful simulation. |
Again I cant fault your logic, and I agree with you completely. :D I just get a bit flighty sometimes when things arent going right, even if I know im doing the right thing haha.
I think Ive made a small breakthrough with the blocking (given your pointer before.) With any luck I will be back with good news soon. |
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In meshing (specially blocking) the approach should always be to : one step back and two steps forward instead One step forward, two steps back. (I am in no way a philosopher :cool:). So abandon old blocking and start from scratch and start to build up things and avoid previous mistakes. Also keep in mind the blocking I have attached (DWP2 made by Simon) |
Just take a look at following threads. It took him around two months or so to get good blocking and mesh (even more as his case very highly complicated but he done it). Really impressive work.
http://www.cfd-online.com/Forums/ans...w-winglet.html http://www.cfd-online.com/Forums/ans...w-winglet.html |
Havent had a chance to read through those links yet (will do that now) but this is my latest attempt. I think that while the blocking is getting closer to what it should be, there are still a lot of problems.
http://img547.imageshack.us/img547/2...ipblocking.png My latest files too. https://www.dropbox.com/s/kyykrrqayg...4AOA_mach4.zip |
Arghhh...Im about ready to give up.
It was all going good...Reasonably nice mesh you say? http://img837.imageshack.us/img837/4526/arghgh1.png ..hey that blocking looks reasonably tidy, you might get a mesh with reasonable quality... http://img546.imageshack.us/img546/4095/arggghh2.png Well if you thought that you would be wrong (as was I). http://img838.imageshack.us/img838/120/arghgh3.png Just thought I was starting to wrap my head around it a bit, but apparently not. Im going to have to call it quits soon. I could be working on this until after the project is due for all I know. Unless I am hit with some epiphany, or some assurance I can reliably build the mesh quickly by the end of the week, I dont want to waste any more time chasing my tail. My last set of files for anyone interested https://www.dropbox.com/s/28fmx3oyyq...OA_mach5_2.zip |
Is it possible that it is some sort of connectivity issue or something? Or possible due to the way I created the O-grid. (Just selected the wing block and no faces like far suggested.) Perhaps I needed to select the face where the wing connects to the wall?
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Does anyone have an idea of what is going wrong here? Ive been doing some googling and stuff and still cant quite figure out what is wrong. I have the impression that its only a small problem, and if I can get it fixed, my mesh should come together nicely.
It is telling me that the highlighted block is the worst block, though perhaps it is a couple of the outlet blocks that is causing an issue. http://img254.imageshack.us/img254/2618/badblock.png This is what happens with the outlet mesh. Perhaps some sort of connectivity or association issue?? http://img833.imageshack.us/img833/6...ewedoutlet.png And there doesnt seem to be a problem with any of the other sides, just when I select the outlet. http://img844.imageshack.us/img844/4...blocksfine.png So does anyone have any thoughts on this, im pretty stuck and could use some input. https://www.dropbox.com/s/28fmx3oyyq...OA_mach5_2.zip |
I´ve just used the "associate edge to surface" tool and "associate face to surface" tool to resolve your problem in your outlet part.
However, I´ve checked your quality determinant 3x3x3 and I think I´ve seen bad elements... https://www.dropbox.com/s/63go4kbobm...OA_mach5_2.rar |
I missed this that last post somehow but thanks for that FJSJ. It seemed to work a treat.
I played around a bit and got the quality up. I got pretty much all the elements above 0.9 for the 3x3x3 determinate, though there are are couple of sketchy elements at the trailing edge mostly (and a handful at the wing tip) http://img442.imageshack.us/img442/655/3by3det.png Problem is now I am getting this weird error when I go to import my mesh into CFX. And it wont load up any of the domains or anything. I have tried renumbering the mesh and creating new parts in attempt to fix the issue but I havent been sucessful yet. http://img96.imageshack.us/img96/3329/argha.png Im so close to being able to run a sim that I can taste it, but have been beaten again! Does anyone have any ideas? latest files: https://www.dropbox.com/s/c972geny1f...oa_mach5_5.zip |
No one has any thoughts on how to fix this error?
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