This is the technical report of the design.

Best regards!

[/FONT]https://www.lisafea.com/citations.html

https://lisafea.com/pdf/Design_of_Ultralight_Aircraft.pdf

- Thread starter christos
- Start date

This is the technical report of the design.

Best regards!

[/FONT]https://www.lisafea.com/citations.html

https://lisafea.com/pdf/Design_of_Ultralight_Aircraft.pdf

Good evening sir! I am sorry about late response, but i am construction engineer and now i am working on pinios' river dam restore and i worked today.

I want to thank you for your interest!

According to your question, i will try to explain you (i think i understand you).

Lisa is a powerful finite element analysis program like ansys, code aster, etc.

If you want to solve a model in one of above softwares you have to:

1) make a 3d mesh model (i prefer stl or step but it is a personal choice)

2) choose materials and put on model

3) make a good 3d elements' grid.

4) choose your support and loads

5)Run it and that is all!

I publish only a technical report and i you can see only the results (of finite element analysis).

But i don't have any problem to share some picture of mesh and grid.

pic1: model

pic2: grid

pic3:material

pic4: material

pic 5: analysis results (visual)

pic 6: analysis results (values)

And one openfoam's analysis animation ( Pressures around the aircraft at speeds just before stall with fully extended flaps)

It will be a really fast and low stall speed aircraft!

Feel free to contact me if need something else!

Best regards!

I want to thank you for your interest!

According to your question, i will try to explain you (i think i understand you).

Lisa is a powerful finite element analysis program like ansys, code aster, etc.

If you want to solve a model in one of above softwares you have to:

1) make a 3d mesh model (i prefer stl or step but it is a personal choice)

2) choose materials and put on model

3) make a good 3d elements' grid.

4) choose your support and loads

5)Run it and that is all!

I publish only a technical report and i you can see only the results (of finite element analysis).

But i don't have any problem to share some picture of mesh and grid.

pic1: model

pic2: grid

pic3:material

pic4: material

pic 5: analysis results (visual)

pic 6: analysis results (values)

And one openfoam's analysis animation ( Pressures around the aircraft at speeds just before stall with fully extended flaps)

It will be a really fast and low stall speed aircraft!

Feel free to contact me if need something else!

Best regards!

Last edited:

you must use "Go Advanced" and load as an attachment (paper clip)

I have a copy of Lisa but found it too difficult to use...the learning curve is high. I use Grape FEA....but it probably is not as powerful.Lisa is a powerful finite element analysis program like ansys, code aster, etc.

What wing airfoil(s) did you use? I have wasted many hours playing with airfoils in XFLR5...

What is the cruise L/D and the L/D max?

Dear sir Doug,Hi christos,

How many points are you using in your CFD grid and how many points do you use to resolve the boundary layer?

Thanks for sharing your results.

Doug

Depended on analysis type. For low speeds (every speed below 0.3 mach is low for fluid dynamics) a k-omega sst model or k-e is a good choice. About boundary layer, is (maybe) the most important subject of turbulence's flow theory. There are a lot of different solutions out there, but i know that the theory is one and you have to calculate y+ correctly for your application and after that design a good mesh with a correct amount of boundary layers.

In my opinion (for k-omega sst model, and low speeds) if you want to run a model and you don't want high accuracy, take value 1 for y+, 20 boundary layers and 15-20 million elements. But it isn't good enough if you want high accuracy (98-99% of experimental one). And it works well in low speeds. Also if you choose k-e, you need a different value of y+.

Also i designed a motorglider and this is a pic of his mesh.

It is a flaperon aircraft. And flaperons operate as cruise flaps also as a result max L/D 21 (25 with retractable landing gear).

What is the cruise L/D and the L/D max?

I would like to notice that fuel consumption is liters per 100km and not liters per hour! yes it still remains economy aircraft. But it is a full laminar flow design and it is well know that this type of aircrafts are efficiently.

EA81 is an excellent also engine. But i will use an A71 one, which is 7-8 kg lighter. I own it and it is (87ps or ~85 hp)version so it is an easy solution for me. Carb'sweight included in fuel and ignition in electrical equipment.

I am planing to use this type of engine because i trust subaru and this engine is getting close to rotax 912 ul so i will be able to compare it with other aircrafts

Thanks for the info. My next question is what kind of a computer are you using to make the calculations and how long does it take?Dear sir Doug,

In my opinion (for k-omega sst model, and low speeds) if you want to run a model and you don't want high accuracy, take value 1 for y+, 20 boundary layers and 15-20 million elements. But it isn't good enough if you want high accuracy (98-99% of experimental one). And it works well in low speeds. Also if you choose k-e, you need a different value of y+.

View attachment 75870

Depends on the solver's settings. The bigger the tolerance the lower the time. But if you choose too big tolerance, could not convergence your solver . I bought core hours and it was simple to me run these models. I don't know exactly how many hours need a pc to run these models, but you need a strong enough pc, at least i5 or i7 and 64 gb ram and (i suppose) something like 30-40 hours for each run. Or lower if you choose a little bigger tolerance. But you will need a lot of hours when you run flutter analysis because it is time depended analysis.Thanks for the info. My next question is what kind of a computer are you using to make the calculations and how long does it take?

Also a good choice is to buy a used workstation (with one or two good processors and big ram) or build a good amd pc. I don't believe that intel's processors are better than amd's for this type of work. You can go with intel but it will be more expensive solution.