Krill profile for high swidths. What is the best profile for the aircraft model

Por_vnyalny analysis of krill profiles for shvidk_snyh maneuverable models

Yuri Arzumanyan

(yuri_la)

Tsya stattya є zagalnennyam discussed at the rc-aviation forum. I talked about the model of repeated combat, i, zokrema, of this type, like in Fig. 1 below.

Mal. 1. Fighting SB-7AS to the club Alisa Air

I didn’t guess at all in the heading of the article, the shards of stagnation below the pidkhid zastosovuetsya not only to the models of the repeated battle. More than that, tsey pidhid buvfirst of all proponing at the dawn of aviation by one of the fathers-founders of modern aerodynamics, our great scientist Mikola Yegorovich Zhukovsky. From these times, the method of proponing it is called the method of N.I. Zhukovsky.

In order not to repeat what was discussed at the forum, I will respect that the information about victorious deputy of a prominent thin symmetrical profile is thin and especially asymmetric profile for soldiers of wine with singing periodicity. Nevipadkovo it seems that the price is new - well forgotten old. Adja to the symmetrical shdo tovstoy profile of the provіdnі bіytsі came not without reason. Behind this are the fates of trials, pardons, the need for compromises and the accumulation of proof.

I don’t dabble in the topic of the lost battle, having left the last time cherubing the cord batt in the pioneer childhood, and I don’t respect myself as an expert in my right. For whom it is more important to study the different forums, the stars there are right athletes, and not just amateurs. I’ll just say that the main arguments for the melancholy of the transition to a more thin asymmetrical, otherwise you’ve already noticed a flat-bulging profile, sound like this:

1) The lower frontal opir of the model, the stars of the higher temple are available for the flight.

2) An hour of direct flight under an hour of battle in a fire is more than an hour of flight in invert, for which a direct flight is important.

3) The most important thing is that the quality of the preparation of the model.

Є Є іnshі peredbachuvanі perevagi, ale stink spіrnі, and I won't tell them. And the main shortfall in this case is the increase in the quality of the pilotage (in the field).

Otzhe, let's get down to matching profiles. It would be better if the result of the analysis is obvious. True, a thinner profile may have a smaller frontal opir. It means that the speed will be greater, and you won’t be able to compete with us! Ale... let's take care of the roses and marvel at how fair it is. For otrimannya numeric results it is required to look at specific characteristics. Therefore, we accept the coming weather data of the model from the photo.

Characteristics of the fighting glider in Fig. one:

Wing span – 1000 mm

Creel area - 20.8 sq. dm.

Golden weight model - 475 grams

Rozrakhunkov's speed of coverage - 32 m/s

Outward profile - symmetrical 15% (NACA 0015 - close to outward)

Motor - Eurgle RC Plane 1580kv D2810 Brushless Outrunner Back Mounting Motor (300W)

Battery - 2200mA 3S 25C

40A regulator

Stand statics:

Gwent - MA 8x5

Strum - 26A

Pressure - 270W

Thrust - 980 gr.

For matching, we take two TsAGI profiles. The first one is a purely flat-swelling profile of TsAGI-719, a visible torso is approximately 10%. Other profile tezh TsAGI, only vins with rounded front edge. Tse TsAGI-831.

Our analysis is seriously relieved by the fact that we can see the wing, which is flying, without the fuselage being turned. Therefore, in the extreme value of the aerodynamic support, it is possible to fix it with a small correction factor, but on the correct results, it is not very much in line.

Schob zdіysniti vіdpovіdnі rozrahunki treba know the aerodynamic characteristics of the skin profile. Pochnemo s flat-pumped.

Table 1. Geometry of the TsAGI-719 profile.

The axis looks like this:

Mal. 2. Contour profile TsAGI-719

And yoga characteristics are in the tables below.

Table 2. Aerodynamic characteristics of the TsAGI-719 airfoil

At rozrakhunkas, you can speed up tabular tributes. Only in the right way to interpolate the interpolation, but inflicting cumbersome charges and vzagali is not easy. In order to get away, I am rooting for it, so that the area of ​​\u200b\u200battack is surrounded by us, it is easy to approximate the table data with an analytical formula. I have seen such approximating formulas for Cx and Su:

Here? - Cut attack in degrees.

We wonder how far away our approximation is.

Mal. 3. Approximation of the aerodynamic characteristics of the TsAGI-719 profile

It can be seen from the graphs that in the zone of small cuts of the attack, analytic formulas are approached by a whole lot of problems.

Table 3. Geometry of the TsAGI-831 profile

The axis looks like this:

Mal. 4. Contour profile TsAGI-831

Aerodynamic characteristics in the tables below.

Table 4. Aerodynamic characteristics of the TsAGI-831 airfoil

For this profile, the following approximating formulas for Cx and Su are given:

de

Mal. 5. Approximation of the aerodynamic characteristics of the TsAGI-831 profile

We have lost to bring the characteristics of a symmetrical profile. Stink Axis:

Table 5. Profile geometry NACA-0015

Such a look may be a symmetrical profile.

Mal. 6. Contour profile NACA-0015

Table 6. Aerodynamic characteristics of the profile NACA-0015

GEOMETRIC CHARACTERISTICS PROFILE

Figure 1. Geometric characteristics of the profile.

Profile chord (b)- A straight line, which connects the two most distant points of the profile.

Tovshchina profile (Сmax)- The value of the maximum profile increase.

Vіdnosna tovshchina profile (С)- Variation of the maximum tovshchina From max to chordi, less pronounced in vіdsotkakh:

Up to 13% is used with a thin or medium profile, over 13% - with a common profile.

Profile curvature (f) - the largest stand in the middle line to the chord, less pronounced in the top hundred.

GEOMETRIC CHARACTERISTICS OF KRILL

The geometrical characteristics of krill are reduced mainly to the characteristics of the shape of the krill in the planet to the characteristics of the profile of the krill. Creelas of modern letakі in the shape of the plan can be buti (Fig. 1): ellipsoid (a), straight (b), trapezoidal (c), arrow-shaped (d) and triangular (e)

The best in aerodynamic weather is an ellipso-like shape, but the wing is folded in the form of a wing, which rarely stagnates. The straight-cut wing is less visible from the look of aerodynamics, and it is also much simpler in preparation. A trapezoidal wing for aerodynamic characteristics is better than a straight-cut one, but it is more foldable when prepared.

Arrow-like and triangular in terms of wing in aerodynamic bearing on subsonic windings, there are trapezoid-like and straight-cut ones, but on subsonic and supersonic windings there are significant shifts. That's why the wings only stagnate on aircrafts that fly on subsonic and supersonic aircraft.

Mal. 1 Form krill at the plan

Mal. 2 Kut transverse V krill

Mal. 3 Geometric characteristics of krill

The shape of the wing in plan is characterized by a span, flattened area, ringing, arrow-like (Fig. 3) and transverse V(Mal. 2)

Krill Waving L are called between kryl kirls in a straight line.

Creel area in the plan S cr surrounded by the contours of the krill.

The area of ​​the trapezoidal and arrow-shaped wings is calculated as the area of ​​two trapezoids

(2.1)

de b 0 - root chord, m;

b to - end chord, m;

- Middle chord of krill, m

Lower wing l is called growing the wingspan of the krill to the middle chord

(2.2)

Like a deputy b equally substituting its value for equality (2.1)

(2.3)

For modern supersonic and subsonic aircraft, the wing height is selected at 2-5. For small aircraft, the value of the wing height can reach 12-15, and for gliders up to 25.

krill sound h called the shutter of the axial chord to the end of the chord

(2.4)

For subsonic aircraft, the sound of the wing does not change 3, but for subsonic and supersonic aircraft it can change in wide ranges.

Kutom sweep c it is called the cut between the line of the leading edge of the wing and the transverse weight of the tail. Arrow likeness can also be cut along the line of foci (to pass on the 1/4 chord line through the ribs of attack) or along the other line of the wing. For supersonic aircraft, it will be 45 °, and for supersonic aircraft - up to 60 °.

Cutom transverse V krill It is called the kut between the transverse veins of the tail and the lower surface of the wing (Fig. 2). In today's litaks, the cut of the transverse V kolivaetsya vіd +5 ° to -15 °.

Creel profile the form of the yogo cross section is called. Profiles can be (Fig. 4): symmetrical and asymmetrical. Non-symmetrical in their line can be biconvex, flat-convex, curved-convex and S-like. Sochevitsepodіbnіbnі and klinopоdіbnі can zastosovuvatisya for supersonic aircraft.

On the current planes, there are mainly symmetrical and biconvex asymmetrical profiles.

The main characteristics of the profile є: profile chord, visible joint, visible curvature (Fig. 5).

Chord profile b is called a straight line, which connects the two most distant points of the profile.

Mal. 4 Shapes of krill profiles

1 - symmetrical; 2 - not symmetrical; 3 - flat-bellied; 4 - biconvex; 5 - S-like; 6 laminations; 7 - coeval-like; 8 - rhomboid; 9 - D visible

Mal. 5 Geometric characteristics of the profile:

b - profile chord; Z max - the largest tovshchina; f max - curvature arrow; x s - coordinate of the largest company

Mal. 6 Kuti krill attacks

Mal. 7 What is the aerodynamic force and the point

R - total aerodynamic force; Y - pyomna force; Q is the force of the frontal support; a- cut attack; q - coolness

za/wikipedia.org

The French company Onera, together with the Italian company Leonardo, tested a smooth wing optimized for laminar flow. As Aviation Week writes, it was tested in a transonic S1MA wind tunnel by a French company. In Denmark, fakhіvtsі analyze data, otrimani pіd h probirovan, prote, zgіdno z previous results, smooth wing showed less frontal support in povіvnyannі zі svіchaynym krill lіtak.

Obsyagi air transport zbіlshuyutsya with skin rock. In order to be satisfied with a drink, having reduced the cost of air transportation and not inflating the income of airlines, retailers are constantly continuing to use new technologies for the supply of aircraft. Zocrema, active work is being carried out near the sphere of reducing the pain of the fire, so near the floor. Tse zavdannya can be done in a number of ways. For example, it is possible to reduce the cost of burning on a sprat of water by painting the design of the engines.

Another way to change the lowering of the fire is to lower the frontal support of the litak. What can be achieved by looking at the design of the aircraft, vicorist and new light materials and coverings. According to the plans of the retailers, the new laminar wing is due to a significantly smaller frontal support at the same time as the standard wing of the aircraft. Such a wing is due to a smooth surface and a low profile, to ensure a laminar flow on a large area.

Laminar wing in aerodynamic tube (levoruch) and thermal image of laminar flow on the upper plane

In the aerodynamic tube, testing was carried out on the left console of the laminar wing of the windmill windmill 5.2 meters. Blowdown testing was carried out at an average flow rate of 0.74 Mach number (913.7 kilometers per year). High-precision thermal imagers were used to wrap around the flowing wing against the flow, which measured the temperature on the wing in real time. As a result, it was found that on the upper plane of the wing of the area covered by laminar flow it became 70 vіdsotkіv, and on the lower 30 vіdsotkіv.

For a daily sizable flying wing of an area covered by a laminar flow, fallow in construction, it should be 30 to 50 vdsotkіv for the upper plane and up to 30 vіdsotkіv - for the lower one. On a part of the wing, there may be a presence of turbulent overflow, which promotes a lot of building. For this purpose, on the modern gliders on the upper plane of the wing, small platings are installed - swirling the flow, which ripples the laminar flow.

Tim is not a mansch, you care what's in civil aviation, let them sound like they do not gain benefits on critical attack points, laminar lowering the wing can be successful in victory. With a stable field without sudden changes in the edge of the attack, a smooth wing can completely reduce the frontal support, which means a slower fire in the field. If the newest wing can appear on serial aircraft, it’s impossible to see.

Today, the Swedish company Saab and the British GKN have achieved smooth wings, optimized for laminar wrapping, by active robots in the gallery. The first part is a composite wing, in which the leading edge and the upper plane are cut into a single detail, with the stitching of other elements and mechanization with minimal gaps. In his line GKN has a great wing, the elements of which are stronger for a better match one to one. Viprobuvannya both kril rozpochnutsya tsoy rock.

In the meantime, at the fierce past fate, GKN was busy with work in the farb gallery, to allow the frontal support of the aircraft to be lowered. Zavdyaky new pokrittam rozrobnikovuyut change frontal opіr 25 vіdsotkіv cruising field. The new Farbi is responsible for saving its power for five years, such a term is the standard for the most important defenses of letaks.

When applied to the body of the aircraft, new farby is responsible for attaching defects and surfaces, protecting them by laminar flow around the aerodynamic surfaces, in the first line of the leading edges, which often muffle the uneven surface.

Vasil Sichov

The most understandable profile, I think, is clear to the skin. Remember, "the photo is in profile and full face" ...

profile of krill in sweat

Just seeming, that is the cross section of the wing (not the wing, but the wing itself, we were at home with you).

However, in a simple way, she doesn’t know, more krill profile- tse, speaking my official, one of the main warehouses that form a lethal apparatus and a light cream, so the wing is still an invisible part. The succulence of such a quantity of profiles makes the whole of the wing, and according to the whole range of the wing, the stench can be different. And in addition, if there will be a stench, there will be a deposit of recognition of a litak and those, like a wine in a litatime. For example, Swedish and high-rise lettuce may be thin krill profile with a gostroy leading edge. Vіdomi representatives of this class are the MIG-25 and MIG-31 aircraft. At the same time, the majority of passenger liners make a profile with a great portability and a rounded front edge.

Types of profiles should be done richly, but the shape of theirs is always crimson. Such a sobi is a strongly twisted horizontal mottle. However, the speckling sounds far away from perfection, because the curvature of the upper and lower surfaces of different types rіzna, like and comradeship of the profile itself. Classic - as long as the bottom is close to the flat, and the top is bulging beyond the singing law. Tse so-called non-symmetrical profile, but also symmetrical, if the top and bottom have the same curvature.

The skin is mathematically protected from the laws of the queen of the aviation sciences of aerodynamics. And then we blow through the aerodynamic tube on different modes for іm_tatsії polotnyh minds and the selection of the necessary characteristics.

Evolution of krill profile. Historical background NASA.

All sorts of tributes can then be collected from retailers of various aviation equipment (including aircraft models to modern aircraft) for the selection of the most suitable option. It is necessary to name the tables of profiles in this way. And the profile of the krill, which we are talking about, is more precisely called aerodynamic krill profile That is why it is one of the main terms used in aerodynamics.

The development of aerodynamic profiles was carried out practically from the beginning of the history of aviation, it is carried out again and again.

Rob tse at special installations. The best representative of such installations in Russia and TsAGI is the Central Aerohydrodynamic Institute named after Professor N.E. Zhukovsky. And in the USA, such functions are being performed by the Doslidnytsky Center near Langley (NASA).

Photos are clickable.

Meta roboti

Follow the profile of the krill without wrapping it around the wingspan, tobto. a wing of inexhaustible scope. Z'yasuvati, how the picture around the profile changes when the attack cut is changed. The follow-up was carried out for three modes - subsonic landing, subsonic cruising and supersonic flights. Appreciate the strength that strength is the support that is on the wing. Wake up the polar krill.

Short theory

Krill profile- Wing slats with a plane parallel to the plane of the flight symmetry (A-A slats). In addition to the profile, it is possible to understand the cut, perpendicular to the front or rear edge of the wing (B-B cut).

Chord profile b - Vіdrіzok, scho z'єdnuє nayvіddalenіshi points of the profile.

wingspan l - Stand between the planes, parallel to the planes of symmetry and tips, where wings are hovering.

Central (root) chordb 0 - a chord near the plane of symmetry.

Kintseva chordb K - a chord in the end section.

Sweep cut along the front edgeχ PC - Kut mizh dotichny to the line of the leading edge and a plane perpendicular to the central chord.

As it was assigned to the front robot, the same aerodynamic force R rozladetsya on pіdёmnu force Y that strength of support X:

Pyomna force and support force are determined by similar formulas:

de C Yі W X- coefіtsієnti pіdёmnoї sily i svoční pіdpovidno;

ρ - Shchіlnіst povіtrya;

V- shvidkіst tіla shkodo poіtrya;

S- Effective body area.

At the end of the day, ring out to the right not self-tightening Yі X, and with їх coefficients C Yі C X .

Let's look at the flow of a thin plate:

If you install a plate to allow the flow (the cut of the attack is equal to zero), the wrapping will be symmetrical. In this way, the potik again, the plate does not breathe and the strength rises Y equals zero. Opir X minimal, but not zero. It will be created by the forces of rubbing the molecules along the surface of the plate. Povna aerodynamic force R minimal and zbіgaєtsya with the force of support X.

Pochnemo giblets vіdhilyati plate. Through the beveling of the stream, the power is rising Y. Opir X Trochs increase through the expansion of the transverse section of the plate along the extension to the flow.

In the world of incremental increase in the kuta of attack, the increase in the bevel of the flow increases the strength. It is obvious that the opera is also growing. Here, indicate what on the small corners of the attack, the power grows significantly faster, lower opir.

In the world of increased kuta attacks, it becomes more and more important for the broken stream to roll around the plate. The power is rising even though it continues to improve, but more, lower earlier. And the axis of the opir grows more and more and more and more, step by step, the growth of the growing power. As a result, the aerodynamic force R start moving back.

And here the picture sharply changes sharply. The winding strings do not seem to be able to smoothly wrap around the upper surface of the plate. Behind the plate is a tight tuft. The rising force is sharply reduced, and the opir is increased. This phenomenon in aerodynamics is called the sight of the flow. "Zirvane" krylo ceases to be krylo. Vono ceases to fly and begins to fall

It is shown that the coefficients of pjomnoe force W Y that strength support W X type of attack α on charts.

Combine two charts into one. On the abscissa axis, we show the value of the coefficient of support W X, and along the y-axis - coefficient of power W Y .

The curve, which has appeared, is called POLAR KRILA - the main graph, which characterizes the power of the krill. Adding on the coordinate axes the value of the coefficients of the pjomnoe force C Y that support C X, this graph shows the value of that directly di ї povnoї aerodynamic force R.

How to take into account that, once again, the flow of water is collapsing C X levoruch, and the center of the grip (the point of reporting of the new aerodynamic force) is located in the center of coordinates, then for the skin s selected earlier cuts of the attack, the vector of the new aerodynamic force will go from the cob of coordinates to the point of the polar, which corresponds to the given cut of the attack. On the polar, you can easily identify three characteristic points of that type of attack: critical, economical, and most vigilant.

Critical hit cut- Tse cut of the attack, when you move it, you see the stream. With whom W Y as much as possible and LA can be minimized at the same time at the minimum possible speed. This is the correct time for landing approach. Look at the point (3) on the little ones.

Economic attack cut- the reason for the attack, for which the aerodynamic support of the krill is minimal. If you put the wing on the economic cut of the attack, it can collapse with maximum speed.

The most powerful attack cut- the reason for the attack, on which the coefficients of the podium force are supported C Y /C X maximum. In this direction, the aerodynamic force is increased to the maximum in the direction of the windward flow. When the wing is installed on the most important point of the attack, it will fly far away.

Aerodynamic quality of krill– price of coefficients C Y /C X when setting the krill to the most important point of attack.

The order of vikonannya roboti

Reference to krill profile:

A great library of aviation profiles can be found on the website of the Illinois University: http://aerospace.illinois.edu/m-selig/ads/coord_database.html

Here, a database of approximately 1600 different krill profiles has been selected. For the skin profile of 12 babies (in *.gif format) there is a table of coordinates of the upper and lower parts of the profile (in *.dat format). The base is in free access, constantly updated. In addition, on this site there is a link to other libraries of profiles.

Choose any profile and capture *.dat file to your computer.

Editing *.dat file with profile coordinates:

Before that, how to import a file with profile coordinates to SW, it is necessary to correct it in Microsoft Excel. And if you open the file in Excel, then all the coordinates will appear in one column.

And we need to coordinate Xі Y profile boules at different stovptsyah.

So we start Excel first, and then open our *.dat file from the new one. The list should indicate "All files". For master texts, the data format is optional - with the symbol-dividing “Probіl”.

Now Xі Y skin coordinates at your stovptsi:

Now we can see row 1 with the text, row 2 from third-party data and empty row 3. We can look at all the coordinates and we can also see empty rows, like stench.

We also add the third step for coordinating Z. For each column, all the middles are filled with zeros.

I change the entire table to the left.

The edited *.dat file is responsible for looking something like this:

Save this file text file(With separate tabulations).

Creation of a profile at SW:

SW is creating a new part.

Run the "Curve through XYZ points" command on the "Elements" tab.

Vіdkryєtsya vіkno:

Press OK and insert the curved profile of the krill into the document.

If it seems to be ahead, that the curve is self-perfecting (it is possible for some profiles), then I will need to manually Excel edit the file in order to use self-permuting.

Now it is necessary to transform this curve into a sketch. For whom we create sketches on the front surface:

We launch the command "Rework objects" on the tab "Eskiz" and as an element for the transformation we specify our curved profile.

If the oscillating curve is narrower than a small diameter (the chord of the profile is only 1 mm!), then with the help of the “Scale objects” command, the profile is increased a thousand times, so that the values ​​of the aerodynamic forces of greater or lesser magnitude become real.

We close the sketch for the help of the team "Vityagna bobishka / base" we see the sketch for a solid model of the headstock 1000 mm. You can really see it for a long time, all one thing mi virishuvatememo zavdannya two-world obtikannya.

Airflow profile in the Flow Simulation module:

It is necessary to blow air on the selected airfoil in three swedish modes: subsonic landing (50 m/s), subsonic cruising (250 m/s) and supersonic (500 m/s) with different cuts of attack: -5°, 0°, 10°, 20°, 30°, 40°.

In case of need, it is necessary to induce pictures at the resection for skin depression and to indicate the strength and strength of the support that is to be applied to the profile.

In this order, it is necessary to complete the following table 18 times in Flow Simulation:

The turn of the wings at the SW is to be followed by the help of the command “Move / copy the body”.

Global parameters to the project: type of plant (filling without fixing closed empty holes), type of fluid medium (replacement, laminar flow and turbulent flow, great numbers Mach for supersonic mode), the speed of the straight axis X V X= 50, 250 and 500 m/s. Other parameters are left for locking.

In the authorities of the rozrakhunk region, it is possible to indicate the type of task - 2D model.

It is possible meta rosrahunka- Poverhneva, put marks for medium swidden Xі Y, as well as for the forces Xі Y.

At the end, there will be 6 graphs - fallows of pidomnoy force Y that strength support X type of attack α , as well as 3 krill polars.

Control nutrition

What is the krill profile?

What is a cut attack?

What is the wingspan?

How does the wrapping of a krill of a terminal rosemah wind up in a vіdkannya of a krill with an inexhaustible rosemary?

What is a krill chord?

Yakі buvayut chordi near the krill?

How to designate the strength of that force of support (formulas)?

How do the graphs of deposition look like C Yі C X type of attack α ?

What is polar krill?

What are the characteristic points on the polar?

What is the aerodynamic quality of the krill?