Questions tagged [airfoil]

The 2D shape of a section of aircraft wing.

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22 views

Reducing camber for DrelaGW19 for L/D ratio

Okay , Thankyou for letting me know But these airfoils (DrelaGW19 and GW27) have extreme camber on upper surface. Now why is that so? (The first reason could be good lift at high Reynolds number(~ 1.5 ...
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1answer
186 views

What airfoil is used on the MQ-1B Predator's wing?

There are lot of UAV's in todays world to be re worked on. The General Atomics series of UCAVs is quite remarkable. I have selected MQ-1B Predator UAV, for an geometric analysis project(undergraduate)....
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2answers
170 views

Swept back wing theory

I'm a beginner in airfoil design. I just came across swept-back wings. There is a point that I couldn't understand that theory. Why is the only perpendicular component of the airflow to the wing(...
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1answer
337 views

What is the airfoil used in the SB13 flying wing?

(Source) What airfoil is used for the wing of this aircraft?
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258 views

Why do X-wing configurations missile/guide bombs use symmetric airfoils?

From all the missiles/guide bombs I have come across, I've always observed that a symmetric airfoil is used for both the wing and tail. Why not have a cambered airfoil for the wing and a symmetric ...
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1answer
9k views

Does lift coefficient vary with the wind velocity for a given angle of attack?

I have this question in my mind. I have been trying to look for this in different books about aerodynamics and I couldn't find the answer. I know I could check the answer experimentally, if I had a ...
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1answer
122 views

Is it better to reduce drag or increase lift?

Essentially my question is, in general is it better to have a lower drag or a larger lift. I know lift to drag ratios are used as an indicator but I think these don't give the best picture. For ...
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1answer
54 views

How does airfoil affect the coefficient of lift vs. AOA slope?

I'm trying to understand whether the airfoil shape can affect the slope of Cl vs. AOA (coefficient of lift vs. angle of attack) in the "linear" portion, e.g., from a few degrees negative to ...
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1answer
89 views

Which airfoil to use for high subsonic flight?

I am desigining an aircraft, which shall fly up to Mach=0.9 in cruise flight in an altitude of 10 km. So when I think of which airfoil to choose, I have to consider aspects like max. lift coefficient ...
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72 views

Why am I getting a low L/D of 4.3 for this supercritical airfoil in Autodesk CFD?

I am a high school student learning to analyze aircraft models in Autodesk CFD for the first time. My current project is analyzing a supercritical airfoil on Autodesk CFD (that was designed in ...
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64 views

What characteristic my canard needs to have when the canard also carries a pair of engine?

I am in 3rd year Aerospace Engineering and trying to do a preliminary design of an airplane. My design has a front wing that also has an engine at its root on both side of the fuselage. There is ...
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1answer
69 views

Could leading-edge dynamic stall occur for a tripped airfoil?

As far as I know leading-edge dynamic stall is characterized by the formation of a Leading edge vortex. This leading edge vortex forms due to the 'bursting' of the LSB (Laminar separation bubble). ...
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1answer
110 views

Why am I seeing extremely high L/D ratio of (e.g. L/D = 90) in my 2D airfoil analysis?

Can anyone explain/justify why, using the 'Theory of Wing Sections' by ABBOTT the lift/drag ratios seem so high. For example, I'm doing an analysis of the NACA0012 airfoil and using their experimental ...
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49 views

How do I find the shear center of an unsymmetrical airfoil?

I'm quite a newbie of these systems and I am designing the wing box of a drone. I know where I want my shear centre. However, I have been trying to determine the shear centre of my idealized airfoil. ...
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1answer
529 views

What's the theoretical background of the critical angle of attack?

The critical angle of attack seems to be at all (most?) airfoils around 15-20°. Why is that? Why is it in this range and not lower or higher? Is it just the result of optimizing airfoils? Or is it ...
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4answers
2k views

Are airfoil profiles patented? If not, why?

For something that takes so much research and can effect performance drastically, there seems to be no patents on airfoils. Too simple in appearance to patent? They appear simple at first but the ...
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1answer
258 views

Calculating CL and CD from Cp vs. x/c graph data? [duplicate]

I need to calculate CL, CD, CM coefficients for NACA 0012 airfoil at angle of attack 6 degrees and Re=7.5e5, Mach=0.05. I used Xfoil for getting the CP distribution, Cp vs. x/c graph and Cp-x-y data. ...
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2answers
106 views

Lift Pressure Distribution [closed]

If the pressure goes always from high to low, we should have a compression, due the lower pressure of the air stream over the upper surface, and an expansion in the airstream in the lower surface. So ...
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2answers
254 views

Why is the aerodynamic center for most airfoils located at the quarter chord location?

I've been reading several sources on the location of the aerodynamic center https://web.mit.edu/16.unified/www/FALL/fluids/Lectures/f03.pdf https://en.wikipedia.org/wiki/Aerodynamic_center John ...
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1answer
191 views

Is co-flow jet wing technology workable?

Coflow Jet claims that their idea of sucking air from the trailing edge and blowing it out the leading edge improves efficiency. But this looks like nothing but flow control done wrong to me. And by ...
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1answer
103 views

How do you calculate the optimal cruising speed of an airfoil?

I am working on a school project (aircraft design). I would like to know how to calculate the cruising speed of a given airfoil. For example, if I have a NACA 5613-35 airfoil (that is the NACA 4 digit ...
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3answers
10k views

Should the pitching moment be up or down?

I had a question regarding the direction of the pitching moment. To make sure we are on the same page, here is what I know so far (please correct me if I am wrong). Lift acts through center of ...
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2answers
5k views

Why are birdlike airfoils not used?

Here are two airfoils (lets focus on Re 100,000): SD7043-il which is simple to build and has a glide ratio of about 60 e376-il a birdlike and much harder to build if using paper or similar due to the ...
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2answers
6k views

What are the differences between symmetrical and cambered airfoils?

I have seen images of cambered and symmetrical wings but apart from that what are the major differences between them? I have also read that symmetric wings don't produce any lift at 0° AOA whereas ...
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1answer
52 views

A question regarding airfoil parameters

If a hypothetical aircraft, which is a tailless straight flying-wing with no fuselage, has the following characteristics: moderate forward sweep an aspect ratio = 9 a dihedral angle of 3 degrees a ...
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1answer
158 views

Why doesn't the centre of pressure move in the case of a symmetric aerofoil?

Why doesn't the CP (centre of pressure) move in the case of a symmetric aerofoil? Also, why does the CP move backward in the case of a flat plate?
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1answer
252 views

How do I choose the vertical tail's airfoil?

I'm designing a fixed wing UAV and I'm having some doubts about how to determinate the vertical tail airfoil. It's important to say that we've already sized this surface. And till this moment we're ...
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4answers
5k views

Why the dynamic pressure is not mentioned in the explanation of lift by Bernoulli's principle?

Usual "explanation" of lift using Bernoulli principle This theory is: Air over the wing is accelerated, its dynamic pressure increases with velocity. The static pressure over the wing decreases (due ...
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1answer
214 views

Leading edge or trailing edge stall?

As I wrote last week, I'm doing a Benedek 10355 airfoil performance report. At this point of the work I am analyzing the stall of the profile at a fixed Reynolds number. The Benedek 10355 airfoil has ...
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2answers
1k views

Aerodynamics of double winglets

I've read here on Aviation SE that the aerodynamics of winglets on an aircraft are easily described as "extending the airfoil". Thus, as I understand it, a winglet is like stretching the airfoil a ...
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1answer
103 views

Is it possible that as the Reynolds number increases, a laminar bubble increases in extension?

I'm studying the Benedek 10355 airfoil (Plot), which should be a profile used in air-controlled models. While I was carrying out a boundary layer analysis, I realized the particularity that I have ...
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1answer
125 views

Pressure distribution on Aircraft wing

While conducting a structural analysis FEA for an aircraft wing, I had to import the CFD pressures acting on the wing, lets say at an A.o.A = 10 deg, at 80 m/s and at sea level, and say the ...
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4answers
310 views

Are there any situations where having high lift but low lift to drag ratio would be beneficial?

From my understanding, high lift to drag ratio could make an aircraft efficient during cruising conditions. This is when the aircraft is in equilibrium, lift is equal to weight, and thrust is equal to ...
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1answer
705 views

How to find the static stall angle of attack for a given airfoil at given Re?

For vertical axis wind turbines applications I'm wondering how one would find the static stall angle of an airfoil at a given Reynold number? Is it just the critical angle of attach (AoA) where ...
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1answer
122 views

Database for NACA airfoil polars [closed]

Is there anywhere where I can find a database of experimental or CFD-obtained NACA series four or series 6 airfoil data? I'd like to have access to a relatively large set of high-fidelity drag polars/$...
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1answer
134 views

What about an airfoil's shape makes air flow faster around it?

An airfoil's shape causes air above the wing to move faster than below the wing to allow for the difference in air pressure as dictated by Bernoulli's principle. This is what many sources say, but I ...
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1k views

Why does my wind tunnel experiment give two different stall angles of attack?

When I increase the angle of attack from 0 to 20 the stall begins at 18 deg. When I decrease the angle of attack from 20 to 0 the stall ends at 13 deg. Why the difference and what value (13 or 18 deg) ...
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1answer
53 views

Is lift/drag the same as coefficient of lift/coefficient of drag?

I see it being used interchangeably (for example by Airfoil Tools Fusion360 AddIn), so can I just pick an airfoil from the airfoiltools database with a certain CL/CD for my aircraft and assume L/D is ...
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3answers
199 views

Would this quadrilateral-shaped airfoil produce lift with a zero angle of attack?

I have been recently studying the shapes and characteristics of different high-lift airfoils that have been used for VTOL aircrafts. While studying these different designs today, a particular ...
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5answers
4k views

Why are the wings of some modern gliders tadpole shaped?

Why are the wings of some modern gliders tadpole shaped, rather than teardrop shaped? An example is the Schleicher ASG 29. Or did they just add a flat plate at the trailing edge for the flaps and ...
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1answer
536 views

How accurate is XFoil / XFLR5 at 'kinda high' Reynolds numbers?

How accurate is XFoil/XFLR5 at Reynolds numbers between 2 million and 10 million? From my understanding it's only accurate at lower Re values.
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3answers
594 views

What is the impact of camber on CLmax?

I was reading Aerodynamics for Engineering Students by Houghton and saw the following graph: A lot of other sources say that increasing camber increases CLmax, like the graph below. I am a little ...
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1answer
83 views

On an aerofoil or circular cylinder why does the airflow stay attached after passing the point of maximum thickness?

Why does it follow the curvature rather than separating? Its not due to the coanda effect as the accelerated flow near the surface of the aerofoil can't be considered a jet. It's not due to surface ...
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1answer
90 views

Comparison of pitching moment at different locations

I've conducted some numerical simulations of a pitching airfoil at three different locations of the pitching axis along the airfoil. The locations (from the leading edge of the airfoil) are: $0.25c$, $...
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1answer
57 views

Can an airfoil have multiple aerodynamic centers?

Aerodynamic center is a point where the moment is independent of angle of attack. Can we have 2 or more such points? Does it necessarily lie inside the airfoil?
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2k views

What are the correct names for the two faces of an airfoil?

When representing a wing airfoil, often the low pressure is on the top side and the lift is positive: In this case upper and lower sides are enough to understand the role of the surfaces, But this is ...
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1answer
100 views

Which among the two contributes most of the lift, the upper or lower surface of the airfoil? [duplicate]

I see some explanations that lift is due to the suction of low pressure on the top surface of the wing and deflecting down of airflow on the bottom which results to upward force lift. I wonder, which ...
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4answers
4k views

Why do airfoil's trailing edges point downward?

The trailing edge of and airfoil is mostly pointing downward. Is there any reason for that? Down wash increases drag and down wash is due to the direction of air pointing down. If the trailing edge is ...
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4answers
4k views

How do I choose the correct airfoil?

I am currently working on a personal single seat, piston aircraft that I would fly myself and I am currently in a bit of conundrum when it comes to my wing design. In this project, I assigned us in 2 ...
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2answers
586 views

What type of airfoil do low-supersonic aircraft use?

I understand that supersonic airfoils have better performance supersonically, but it seems at if they are not always used for any aircraft that goes supersonic and that supercritical airfoils are ...

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