Developing Fractal Algorithm for Fluid Dynamics

[kram1032]

mass, however, DOES hinder accellerations of any kinds and thus could potentially slow down any wing movement.
F=m a or a=F/m - the higher the mass, the stronger Force you need to give the same accelleration.

It at the very least requires a test. Try making the same two designs but with at least almost equal mass in each case.

[freshNfunky]

mass, however, DOES hinder accellerations of any kinds and thus could potentially slow down any wing movement.
F=m a or a=F/m - the higher the mass, the stronger Force you need to give the same accelleration.

It at the very least requires a test. Try making the same two designs but with at least almost equal mass in each case.

your concerns in Honour. But please explain how stating a physical formula about forces and their corelation between mass
and acceleration, adds a certain agrument into this question of self-regulation of a profile? where do you see 2 gramms acting
to lead into this kind of reasonable difference, rather than adding a 'little' inertia of factor 1.1?
how can 2 gramms be able to damp turbulence this way?

While the conventional profile quickly gets in to an uncontrollable behaviour you state adding two gramms would fix this?
ok maybe i will have time to make an additional wind tunnel test adding the missing two gramms to proove,
that it is not just weight who causes this self-regulating behaivour...

[Madman]

It's not only the absolute mass, but also where you put it. You put all mass before the lift point, moving the center of gravity to the front, thus stabilizing the design.

Your explanation why your unmodified glider stalls is untrue. I can make your unmodified model perform perfectly without active steering by modifying the center of gravity and maybe a wee bit of tweaking on the stabilizer...

BTW, when are you ready for the real life test I proposed? I'm waiting for a date/time and a place! (In case you forgot, see reply #17 in this thread).

[cKleinhuis]

My five cents

regarding additional weight that is obviously not placed to stabilize the plane, i mean by placing additional weight on the planes would you expect such behaviour?

Making those flares thinner and weigh more would certainly flow into a final design, nevertheless it proves somehow the concept

i personally am not an expert at this but i have folded many paper planes in my life and when folding the back of a wing up it is performing a loop, this effect is in my eyes what we observe here due to the flexibility of the upward fold it does not perform a loop but just stabilizes the horizontal direction. . .

[freshNfunky]

It's not only the absolute mass, but also where you put it. You put all mass before the lift point, moving the center of gravity to the front, thus stabilizing the design.

that is so far correct to keep the plane stable at a certain cruising speed. but the nose will rise if you increase speed and thus lift.
it's thus just a matter of speed if this effect takes place or not and the outbalancing of the center of gravity makes it just better to steer and stable at its
general cruising speed.

The test performed in the wind tunnel is also independent where you put the center of gravity. you can attach the threads at the nose or further to the
trailing edge. the result will be always simmilar.

BTW, when are you ready for the real life test I proposed? I'm waiting for a date/time and a place! (In case you forgot, see reply #17 in this thread).

location: nearby munich germany, time: unknown in the future. Due i am currently very buisy with developing, creating presentations articles asf.
this is not an excuse but rather trying to sort important things from unimportant in my dense scedule.

[jehovajah]

Madman, because you do fly i think you have some intuitive data that will be very useful.

Turbulence is the big issue in fluid mechanics, and key to better understanding how aerofoils actually behave under stress in flight.
Have you actually flown through turbulence? What is it like, and what corrective behaviours do you have to follow?

Do you have any intuitive solutions to aerofoil design that would make control through these surfaces easier?

In Aerohydrodynamics we are still at that stage where intuition computes better and faster than CFD!

[Madman]

that is so far correct to keep the plane stable at a certain cruising speed. but the nose will rise if you increase speed and thus lift.

How would you increase speed on a glider if you have stable flight and no active steering?

The test performed in the wind tunnel is also independent where you put the center of gravity. you can attach the threads at the nose or further to the
trailing edge. the result will be always simmilar.

Not true. If you move the threads further to the nose, both designs will be more stable. The lighter design will look more instable though, because it follows the turbulent flow better (less inertial effects).

location: nearby munich germany, time: unknown in the future. Due i am currently very buisy with developing, creating presentations articles asf.
this is not an excuse but rather trying to sort important things from unimportant in my dense scedule.

Okay, that's fair. Although you may want to reevaluate the importance of a real world test 

Turbulence is the big issue in fluid mechanics, and key to better understanding how aerofoils actually behave under stress in flight.
Have you actually flown through turbulence? What is it like, and what corrective behaviours do you have to follow?

Yup, I've been on the wrong side of Pic de Bure in the Alps during Mistral... I think that qualifies as flying through turbulence  I lost 4 meters of Mylar sealing there... No big issue, but the sound of ripping tape freaked me out for a second  . There's only one thing you can do if you fall out of the sky and that is to push the stick forward ( I know, it sounds a little counter-intuitive).

Do you have any intuitive solutions to aerofoil design that would make control through these surfaces easier?

Nope, I think we've passed the point in time where intuitive solutions work for better controls. The thing that counts is to keep the boundary layer on the aerofoil, especially at your control surfaces, at all times, preferably at low speed. FnF's tests show the boundary layer letting go. The big question is if it is just an indicator (like taping yarn on your wing that show the moment/place and time when the boundary layer disappears) or if it actually reduces the effect of losing the boundary layer. If the latter is the case, the added drag by adding the "post-it memo's" will have to be eliminated at normal or high speeds to create any benefits in aerofoil design.

[freshNfunky]

How would you increase speed on a glider if you have stable flight and no active steering?

downhill, motor, you have many options we'll leave the motor out for now. what remains is the downhill speed.

Not true. If you move the threads further to the nose, both designs will be more stable. The lighter design will look more instable though, because it follows the turbulent flow better (less inertial effects).

sorry all tests independant of the thread positions were almost equal in showing the same fluttering effect.

The thing that counts is to keep the boundary layer on the aerofoil, especially at your control surfaces, at all times, preferably at low speed. FnF's tests show the boundary layer letting go. The big question is if it is just an indicator (like taping yarn on your wing that show the moment/place and time when the boundary layer disappears) or if it actually reduces the effect of losing the boundary layer. If the latter is the case, the added drag by adding the "post-it memo's" will have to be eliminated at normal or high speeds to create any benefits in aerofoil design.

a almost fully developed laminar and unseparated boundary layer is only guaranteed if your wing is free of any dead flies and you keep the designated speed limit. laminar profiles are only suited for their designated speed. outside the designed cruising speed the ideal aerodynamic body is variing, also when cruising curves or flying through turbulence. your rigid profile no longer develops an attached boundary layer but starts to detach. the more smooth and rigit, the more sensitive your airfoil reacts. finally a rigit airfoil will always be worse, because it cannot adapt its ideal aerodynamic body according to the current situation. It also fails in turbulent environments like usual in konvection flights during soaring.

Further in this stage of attack angle shown in the video you will have boundary layer separation on the adaptive and classic airfoil. but with the classical profile it's much more sensitive which then creates the fluttering effect because the normal airfoil can't hold the air and stalls. it's also called dynamic Stall. Different to the adaptive airfoil which still can create lift at these angles. The idea behind the postits lifting up in critical situations is to increase Ca_max and further to control turbulence, which is well demonstrated. drag only counts in normal flight which so far shows no negative results.

the final L/D diagrams will come soon.

[jehovajah]

Now we're Talking sense! Thanks, both of you! It gives me insights and connections.

[Madman]

OK, let me try to understand you FnF...

downhill, motor, you have many options we'll leave the motor out for now. what remains is the downhill speed.

When I'm flying, I am not linked to the ground, so how am I going to increase downhill speed? If I'm in a stable flight, nothing will change unless I disturb my flight. If the design of my glider is good and stable, disturbances caused by air turbulence will cause a change in flight pattern, but the glider will in the end return to a state of equilibrium. In fact, when I'm flying with beginning pupils, I often tell them to let go of the stick since the glider will fly more stable when they don't mess around with the controls 

sorry all tests independant of the thread positions were almost equal in showing the same fluttering effect.

If that is true, then that substantiates the theory that the effect is caused by inertia and not by aerodynamic effects. Although I would expect some increase in stability if you moved the axis more to the front...

OK, now for the somewhat more difficult part...

a almost fully developed laminar and unseparated boundary layer is only guaranteed if your wing is free of any dead flies and you keep the designated speed limit. laminar profiles are only suited for their designated speed. outside the designed cruising speed the ideal aerodynamic body is varying, also when cruising curves or flying through turbulence. your rigid profile no longer develops an attached boundary layer but starts to detach. the more smooth and rigit, the more sensitive your airfoil reacts. finally a rigit airfoil will always be worse, because it cannot adapt its ideal aerodynamic body according to the current situation. It also fails in turbulent environments like usual in konvection flights during soaring.

Further in this stage of attack angle shown in the video you will have boundary layer separation on the adaptive and classic airfoil. but with the classical profile it's much more sensitive which then creates the fluttering effect because the normal airfoil can't hold the air and stalls. it's also called dynamic Stall. Different to the adaptive airfoil which still can create lift at these angles. The idea behind the postits lifting up in critical situations is to increase Ca_max and further to control turbulence, which is well demonstrated. drag only counts in normal flight which so far shows no negative results.

There's a lot of truth in what you say here. Dead flies and raindrops can create havoc to the airflow around wings, especially around older profile designs. The problem is that that's an issue at all speeds, but gets worse at higher speeds. And that's the reason why I don't believe that your theory will work. I admit, I have no idea what your post-its do at low speed. They may or may not improve stalling behavior. The C_L/C_D curves in some of your links show some improvement there. The bad thing is that they will increase drag at higher speeds as much as dead flies will. And in the end, performance at high (cruising) speeds is just more important then at low (landing) speeds.

[jehovajah]

It is incredible that the flap of a butterfly wing could cause a tornado somewhere in the atmosphere, but dead flies can make a glider drop out of the skies!

The confidence you have in a good aerofoil design belies the fact that the stability is very much dependent on a limited set of atmospheric circumstances, and your ability to know what to do if those change detrimentally. I guess that assessment applies to most things we humans love to do!

You identify 2 goals :speed and stability. Can a single surface meet both optimally, or can a variable surface do that better?

[Madman]

dead flies can make a glider drop out of the skies!

That's putting it a bit strongly, but it doesn't improve the glide slope... 

The confidence you have in a good aerofoil design belies the fact that the stability is very much dependent on a limited set of atmospheric circumstances, and your ability to know what to do if those change detrimentally. I guess that assessment applies to most things we humans love to do!

You identify 2 goals :speed and stability. Can a single surface meet both optimally, or can a variable surface do that better?

I did not say that a variable aerofoil profile wouldn't be better. In fact, I can adjust my profile to the speed I'm flying by selecting different flap settings. If you look at airliners, they have even more tricks to be able to use the same wing over a (much) larger speed range, like fowler flaps and slats. I have my doubts however about having turbulence decide what my profile should be. That's also why the comparison to landing birds goes astray; the reason that a bird has his wings almost perpendicular to the airflow during landing is to reduce energy and speed fast, so it is able to land without breaking its legs... The fact that turbulence causes some feathers to stand out in all directions is not a goal, but an effect, contrary to what FnF wants us to believe.

[jehovajah]

Fresh and Funky, please try a flight of your glider with one wing normal and the other modified, of course the wings should be weigh balanced.

Madman how do you predict the flight path?
FreshnFunky how do you predict the flight path?
Then lets see the video evidence.

[freshNfunky]

Die polar diagrams are now evaluated.
Evaluation and publication here:
http://www.felixschaller.com/index.php/blog/blog-news/30-general-news/83-measurements-01