# Lifting line theory numeric estimation

1. Aug 10, 2007

### lnpsivan

hi,

i am in the final yr aerospace engg.....i am trying to write a program on matlab to calculate the lift distribution over a wing using the numerical estimation based on the classic(prandtl) lifting line theory...however, due to my relatively limited exposure to matlab i am having trouble putting the entire claculation process into an iterative loop....hence...any advice on possible references or similar programs would greatly help.....

one other issue is that.......in matlab...if i say

for x=1:1:3
y=2*x
end

how should i alter t above command to make all the values of y thru this loop get stored in a "y" matrix. i.e. wat command shud i put to get a result like this
y=2 4 6

any constructive advice is much appriciated...

thanx

2. Oct 18, 2007

### vitorpy

x = 1:1:3
y = x.*2;

no need for this kind of iteration in matlab, you should work with vectors. good practice, and a lot faster.

3. Oct 18, 2007

### lnpsivan

yes i realized that....nevertheless thanx for the advice..much appriciated....

from the time i posted the first entry in this thread i hav gone on to write 5 aerodynamic analysis programs in MATLAB.....

-flat plate solution for "n" lumped vortex at an angle "alpha" to flow;
-numeric lifting line program to estimate aerodynamic properties of wing, even in the stall region
-flat plate in ground effect, studies chord-wise ground effect
-numeric lifting line thoery applied to wing in ground effect, studies span-wise ground effect
-detailed Fourier series estimation of aerodynamic properties of wing with taper, geometric and aerodynamic twist.

in case anybody is having trouble in any of the above areas do approach me, i am sure i would have had them too....

and in case anyone wants these program jus leave a message and i shall pm....

4. Oct 18, 2007

### vitorpy

Have any idea for lift distribution on swept wings biplanes? Trying to find a solution without using off the shelf panel methods software.

Thanks guy!

And I make the same offer, if you need some help with Matlab, feel free to drop a question! =)

5. Oct 18, 2007

### lnpsivan

thanx for the offer.....

about your question..i need to think...if i can recall there are/were only a very few swept wing bi-planes

y would u need it? if i may ask....

vortex panel method cant cater for sweep, unless you are trying calculate the normal component of the flow as the wing "sees". but this result would not be too accurate given there is alot of span-wise flow---this explanation can be aplied to monoplanes as well as biplanes

more-over using vortex panel method, one can get very good estimation of aerodynamic properties of airfoil sections not wings...so...not sure how ur goin abt it....

sorry, don hav any direct answers, would need to kno a bit more background before giving my opinion...

Last edited: Oct 19, 2007
6. Oct 19, 2007

### vitorpy

lnpsivan,
Thanks for the attention.

Developing next year airplane for SAE AeroDesign competition =) Biplanes with swept wings became a common choice (at least in South American competition) due to competition requirements and rules.

We can get a good analysis for flow using traditional finite element method, but the referees seems to prefer panel methods. I'm not really all into them, since in my background (fluid mechanics for reservoir engineering) FEM appears to be more common.

I'm the member of team responsible for simulations, but my background and knowledge is not really suited for aerodynamics. I'm spending a lot of weekends with Raymer and Roskem by my side these days =)

We used an airplane with this kind of configuration last year (competition was held just a few weeks ago), and it worked well. But for next competition we want better theoretical foundations for our choices.

If you can give any advice, it will be really appreciated.

Thank you in advance,

7. Oct 21, 2007

### lnpsivan

off the top of my head...i am not sure so don want to advice..but in case somethin does come up..shall pass on t info...sorry wasnt of any direct help...

8. Oct 21, 2007

### vitorpy

Oh, ok =)

Thank you, anyway =)

9. Apr 15, 2008

### mohit

hi i am 2nd year engg student doing project on ground effect.due to my limited knowledge on matlab i am not able to write the code.can u plz mail me the prog as soon as possible.
rawmohit@gmail.com

10. Apr 15, 2008

### lnpsivan

mohit, hav sent an email....pls check ur mail....

11. May 22, 2008

### wilkinsi

would you happen to have your codes posted somewhere. I a script for the numerical Lifting Line Theroy and Vortex Lattice methods. I was hoping there would be some similarities there to compare.
I am a fourth year ASE major.

Shari

12. May 23, 2008

### loptr

I am a final year aerospace student, and I would greatly appreciate it is you could send me this code. I will pm my email address. Thanks.

13. Jun 25, 2008

### Cespo

hi guys,
i'm in trouble tryng to build a code using Panel Method (lattice) to estimate aerodynamic properties of a sail, given the geometry.

lnpsivan, could you give me the
"detailed Fourier series estimation of aerodynamic properties of wing with taper, geometric and aerodynamic twist"

then i'll have to fit it to the asymmetrical geometry of a sail, cold it work?

14. Nov 27, 2008

### nicholasc

Hi lnpsivan,

I refer to your message posted a few months back. I hope that you still have the program for lumped-vortex? I was struggling to model the lumped vortex using MATLAB. Can I please have a copy of your program? Here is my email address: nickychia@hotmail.com

Cheers,
Nicholas

15. Feb 1, 2009

### cueca

before coding, i suggest some supplementary books or Reports

* Katz, Plotkin. "Low speed aerodynamics" -for theory
* Galuert, "elements of airfoil and airscrew theory" -basic book
* James C. sivells, Robert H. Nelly "Method for calculating wing characteristics by ligting-line theory using nonlinear section lift data", NACA TN, 1269 (avaible at ntrs.nasa.gov)
Last report NACA TN. 1269 builds an iterative method and uses fourier coeff. Method may be used both linear and nonlinear section data and for symmetric,asymmetric anti symmetric cases. I am working on it for very long time.
But before spending time with it i suggest Andersson's "fundementals of aerodynamics". Just read related part for linear solution(NxN) matrix will be solved (assuming 2d lift curve slope 2pi)
I wrote that at first then i tried the non*linear code with a iteration procedure which i failed.
The explanation for that is not clear so i suggest Naca 1269 instead. But it is too detailed and dervation of formulas takes very long time.
Anyway, i write the codes with vB 6.0 (simple, user friendly and very good front page )
In the past i wrote some VLM codes for single wing and ground effect (it scans a range of dihedral angles to estimate the lift curve slope on gorund effect.)
If anyone wants too see it i can send the code or the compiled code (.exe)
If anyone interests with nonlinear solutions with lifting line and have an experience i would like to worj together or get his/her help for my studies.
Thanks, Tolga

16. Feb 18, 2009

### fly

hello
I'm studying mechanical engineering in zürich.
Does somebody have experiences with non-symmetrical flow. I have to simulate a lifting line model for yaw angles which are not zero (sideslip) for different airplane configurations, i wrote a matlab code which works for yaw angles=0 but for other angles I have great numerical problems.
Does anybody know some Literature where the Problem sideslip is described?
Thanks Fly

17. Feb 19, 2009

### cueca

try NACA report 1269 by M. J. QUEIJO
you may find it on ntrs.nasa.gov
if it doent suits you, look to the reference page of the report.
Report uses 1 chordwise panel vortex lattice method (may be said as numerical lifting line method , but lifting line can be swept.) You will have to find the circulation distribution of each step of vortex lattice, and to do this you will have to solve a lineer equation of NxN

18. Feb 20, 2009

### fly

thanks for the reply. I know this report. Barely its just for a symmetrical flight, also the sample calculations. Do you know some sample calculations of the lift distribution for sideslip? I search some, because my code gives me really strange results in sideslip(there are a lot of numerical problems). The results for a normal straight flight are really good! My code is based on the book ''Aérodynamique subsonique Ion Paraschivoiu'' I want to send you some pictures of my calculations, then I can explain better my problem. Works this in this forum?
fly

19. Feb 20, 2009

### cueca

you mean asymmetrical lift distribution without any ailerons or asymmetrical flaps deflected? (Still a symmetrical geometry but only a sideslip angle occurs)
Or you mean a deformation on lift distribution due to ailerons deflected.

This two models are different.
Have you visualised your lift distribution on asymmetrical case?
you can send pictures me by email
tuncer_tolga@hotmail.com
If you tell me what exactly your model, i can send some links for sample calculation .

20. Aug 26, 2009

### monkeyman_72

Hey, I'm currently doing my finial year in aerospace engineering and was just wondering if I could get any advise on some work I am doing. Currently I am trying to develop a matlab code for the lifting line theory that will be able to take into account wing twist.
I'm trying to test a morphing wing compared to a standard wing so I need it to be able to model differences in twist and aileron deflection but I'm little lost at the moment. I just need some preliminary data before I complete a model in CFD. If anyone has any ideas about how to model them in a why in which I can compare results or even just ideas about how to model the wing twist that would be a great help, thanks.
Also i'm happy for any to pm me or email me on monkeyman_72@hotmail.com