Model assemble - meshing strategy
 

Hello again. So here is a description of the situation.

My geometry comprises of :
1. fuselage, 2. wing, 3. winglets (whitcomb), 4. pylon, 5. nacelle and 6.turbine.

I assembled them in 1 model. To be more precise, first I put the fuselage bits together. Then the wing and I added it to the fuselage. Afterwards the pylon. Then the nacelle and the engine and I assembled them with the pylon and then I added this selection to the fuselage-wing model. Finally, I assembled the model of each winglet and added those to the rest as well. Each time I used different tolerances in order to get the model assembled.

However, when I try to split the to remove the turbine let's say, the winglets are removed from the model too and then I cannot add them again. The same happens if I try to add a model. For instance, I realised that when I was putting the pylon together, I forgot a surface that sits on the engine so I created the coons patch and its model but when I added it to the greater model, the winglets came off again (and I couldn't understand if this surface was indeed added to the model)

What am I doing wrong? :(


I have attached 2 pictures to help you understand how the geometry is. The part that I want to add is the part of the pylon that sits on the turbine (figure 1).
Please notice that the turbine does not end where the nacelle ends and the engine is actually hollow so air goes through (figure 2) and therefore I can't use the tutorial (mainly because they don't end at the same plane). Do you have any suggestion as to a meshing strategy for this region? I've meshed the rest of the aircraft and this is my last problem. I'm thinking of removing the turbine and the bottom part of the nacelle because it adds unnecessary complexity (I think I could live with the missing parts especially when setting up the boundary conditions). That's why I wanted to split the model (and the winglets came off).

I would really appreciate it if you could offer a piece of advice.


Lefteris


Update

Well, I deleted the turbine and the bottom of the pylon, tried to reassemble the whole model and this time the winglets were added. It seems rather random because I didn't do anything different... only the tolerance was difference but much much smaller!

This definitely sounds like some weird behavior. Glad to hear you've got it working.

A clarification here. Only a single tolerance is used within a model. Applying one tolerance at one point and then another tolerance later means the actual tolerance used for each piece of the entire model is the last one.

Just to be clear here's a silly analogy. You have 5 pieces of wood you want to glue into one. You glue the first two together with red colored glue. Then glue the third piece to first two with blue glue. The fourth to the three with green glue. And the fifth to the four with white glue. The final assembly does have not red, blue, green and white glue but _only_ white.

It sounds strange but the reason it's like this is because every time you add a piece it's essentially re-assembling the whole model.

Ah, I see! It's good that you made this clarification and set this straight.
Initially I thought that as long as I put some parts together they will be fixed with each other irrespectivelly of the tolerance I use later to add more (sub-) models.
Lesson learnt then: The last tolerance is applied to the whole model.

Thanks Chris!

Hi Lefteris,

My question is not about meshing, I was curious to ask for the very long. Somehow I decided to ask it today. Speaking based on the pictures you posted, is this SUGAR volt geometry?

If it is, could you help me to find the open geometry for this model?
If it is not an open geometry, could you give some hints to find a good source explaining the design and introducing usable information for being able to reproduce the model?

I am interested in conducting an study around new models.

~<~ I am just updating my post, sorry about my mistake I already have the NASA report on this model, but haven't time to go into it thoroughly. However, if it is a open geometry I would happy to know where I can find it. Thanks again. ~>~
Cheers,
Payam

Hi Payam!

Apologies I didn't reply sooner.

To the best of my knowledge this is not an open source geometry.

There are lots of papers around however. You might want to look for High (or very high) Aspect Ratio wings (>20), or Strut Braced High Aspect Ratio Wings. It would also be a good idea to read a couple of papers for laminar flow wings as well but any laminar aerofoil should do if you're interested just in the general concept.

If my memory serves me right, cruise Mach is about 0.7 at 35000ft (however, if they want to address all environmental issues somehow, the cruise altitude should be higher than 38000 to minimise the chance of forming contrails, in my opinion) and the aircraft is generally similar to the 737 (payload, range). For all I know, you could just use the same fuselage, neglecting any differences in the vertical and horizontal stabilisers). I think the final NASA report has some dimensions but I'm not sure. In any case the span should be less than 80m (the wing does not fold, YET) so knowing the span and AR you can work out the chord at root and you can also assume a small leading edge sweep angle so that cross flow instabilities are not a transition mechanism. The trailing edge has a kink at about half-span (half-span, of the half-wing but this is fairly obvious :P), before the kink the TE has zero sweep.
You can also introduce in your design some small anhedral.
Another "detail" is the wing-strut junction is just before the kink on the wing.

I'm not sure if any of these help but drop me a line if you have any other question!

Yep, you were right. This isn't an open geometry.

Thank you for the response. I read the NASA report entirely entitled "Phase II: N+4 Advanced Concept Development." They gave dimensions with almost every detail on four models (TS1 to TS4).

However, thanks a lot for the points, clarifying wing-strut junction and kink locations. I will gave this concept a try.

Bests,
Payam

Aw I didn't have that report, I just read it. I had stopped at N+3 :p lol
They do give a detailed description then! I was given the CAD "as is" so I didn't bother looking for dimensions in the reports.

I'll try to go over my notes this weekend to see if I can find anything that can be useful in your research.

Thanks for your time, Much appreciated.