Questions tagged [airfoil]

The 2D shape of a section of aircraft wing.

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3
votes
2answers
320 views

What are the scale effects of GA wing tip airfoils?

[ update: I am adopting an improved description provided by Peter Kämpf: "...only looking at the airfoils in isolation..." ] The goal of this question is to determine if wing tip airfoil scale plays ...
3
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1answer
924 views

What is decalage and how it affects airplane performance?

What is decalage in airplanes and how important is it in respect to airplane performance?
3
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1answer
6k views

How to select the most efficient airfoil for low speed flight?

What airfoil (or family) has the highest $C_L/C_D$ ratio at speeds in the $50\:km/h$ range. The use case would be an ultralight with a max speed of $50\:km/h$
3
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2answers
758 views

Is flow turning different from the Magnus Effect? If so, how?

The production of lift is much more complex than a simple differential pressure between upper and lower airfoil surfaces. In fact, many lifting airfoils do not have an upper surface longer than ...
3
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1answer
104 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 ...
3
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1answer
490 views

When calculating the lift coefficient, what area is used?

Lets say I had this rectangular double curve wing. Orange represents the chord length, red represents the airfoil outline length below the chord line, green represents the airfoil outline length above ...
3
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2answers
166 views

How can I tell from the location of flow separation if an airfoil is stalled?

I am in the process of completing a carbon airfoil for my track car (sedan) and I am looking to determine stall angle visually. AKA, wool tufts and highway runs with my GoPro pointed upward from the ...
3
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1answer
909 views

What does leading edge radius mean?

What does leading edge radius mean amongst these parameters of a st cyr 24 airfoil?
3
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2answers
10k views

How does centre of pressure change with angle of attack?

I've been given the distance of centre of pressure from the leading edge with a certain angle of attack and was wondering if it's possible to calculate the new position when the angle of attack ...
3
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1answer
700 views

Why is the numerically determined location of the center of pressure inaccurate near Cl = 0?

I am working on an assignment and I need to calculate the center of pressure of an airfoil, through a numerical method (the panel method). I am getting a weird result because it gives its position on ...
3
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2answers
198 views

Shouldn't the upwash on an airfoil increase the effective angle of attack?

From what I understand, induced drag comes from a reduction of the effective angle seen by the airfoil. However, from wind tunnel smoke visualization, we can see that the streamlines at the leading ...
3
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1answer
1k views

How to calculate the lift coefficient of a multi element airfoil?

How to calculate the lift coefficient of an airfoil section with flaps and slats if we know the Cl for the individual elements, like Cl of wing, Cl of slat and Cl of flap?
3
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2answers
1k views

What are Uses of thin airfoil and thick airfoil?

I have heard that thin airfoils are used for fast fyling and thick airfoil a are used for more lift. Is it true? Can you explain specific uses of thick and thin airfoils ?
3
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1answer
900 views

Are there any reference values for Cl and Cd of a NACA 0012 airfoil to verify CFD simulations?

I am having trouble finding the established results of inviscid flow CL and Cd variation over NACA 0012 airfoil, for the transonic region. I need the data to verify the results I am getting through my ...
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2answers
2k views

Is airfoil thickness proportional to drag coefficient?

Does increase in the thickness of a camber airfoil mean more drag will be produced? Why do slow flying planes have thick airfoils when it will just slow them down even more?
2
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1answer
664 views

How to calculate airfoil geometry with the maximum lift to drag ratio for a given Reynolds number?

How does one determine the optimal cross sectional geometry to maximize Cl/Cd?
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1answer
263 views

What airfoil simulation software is suitable for a cut trailing edge?

I'm looking for a way to simulate airfoils used to reduce turbulence. airfoiltools.com already does this a long way. However I have width and length limits, and I'm interested in comparing full ...
2
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1answer
948 views

Why is this airfoil curved upwards on the bottom part of the airfoil?

Image source datawiki.net Is this to slow down airspeed. I know that the high pressure and low pressure above and below the wing both contribute to downwash, but how does this airfoil form downwash?
2
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1answer
257 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 ...
2
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1answer
296 views

How much lift do supercritical airfoils produce?

Compared to your regular asymmetric cambered airfoil, How much does lift do supercritical airfoils produce?
2
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1answer
175 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?
2
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3answers
2k views

What is the “Centre of Pressure”?

This question may sound naive but surprisingly it puzzles me. A wing has a centre of pressure, does it mean that lift acts on point and not on the whole chord of an airfoil?
2
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1answer
315 views

How are wingtips attached to the aerofoil while maintaining structural rigidity?

I've been trying to research various methods on the joints between the winglet and the wingtip out of interest. I'm aware that the airfoil is attached to the underbody of the fuselage by means of a ...
2
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3answers
649 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 ...
2
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1answer
73 views

How do viscous drag and form drag individually change as a function of angle of attack?

Typically, when dealing with airfoils, the drag coefficient $C_d$ is given as a function of angle of attack. If we limit the discussion to 2D subsonic incompressible flows, then the drag is the sum of ...
2
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2answers
156 views

Vertical autorotation with passive rotor

Let's say we have a simple hollow cube(chosen for simplicity) with outside side length=10cm, thickness=5mm (or another arbitrary shape with arbitrary dimensions). Clarification: I am NOT talking ...
2
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3answers
168 views

Fabric-covered Clark Y Max Coefficient of Lift

I'm looking at the Aeronca C-3 Collegian, which had a Clark Y airfoil, and I'm finding the following: Wing area: 142 ft² Empty weight: 466 lbs Payload: 470 lbs Stall speed: 38 mph When I do the math ...
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2answers
880 views

How does the thickness of a wing affect its aspect ratio?

As far as I understand, the aspect ratio equals the wingspan divided by the chord or the square of the wingspan divided by the wing area. Given this formula factoring in only the wingspan, the chord, ...
2
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1answer
477 views

How do KFm step airfoils work?

I was looking for airfoils, and I came across an interesting design. It's called a KFm1 step airfoil. Those of you in model aircraft design might have heard of it. However, I've never really seen one ...
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1answer
361 views

Where can I find the aerofoil geometry of a commercial aircraft so as to design it in CAD software?

As a part of my final year thesis, I need to design a commercial aerofoil for an existing aircraft (such as Boeing/Airbus) to conduct some FEA & CFD analysis. I've been trying to source aerofoil ...
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1answer
122 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 ...
2
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1answer
85 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 ...
2
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1answer
136 views

What causes the vortex on the tip of this vertical stabilizer (CFD Simulation)

This is a computational fluid dynamics simulation of an airfoil that is oriented to look like a vertical stabilizer. After watching the video, it becomes clear that the tip of the stabilizer causes a ...
2
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1answer
341 views

Would adding a slat and a slotted flap increase the max CL of a multi element airfoil to 6.5?

Would adding a slat and a slotted flap increase the of a multi element foil to 6.5? I understand, as a general rule, the max $C_L$ for a classic NACA airfoil is as follows: Base: 1.5 Slat: + 0.7 ...
2
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1answer
393 views

Why are hexa airfoils used on rockets despite having more drag that diamond airfoils? [closed]

I was doing a study on airfoils shape for a rocket. I tested the diamond and the hexagonal airfoil with Missile DatCom, RasAero and the Shock Expansion theory and from my results it seems like the ...
2
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1answer
219 views

How (or where) do I find an airfoil optimized for low reynolds numbers (100,000~150,000)?

Looking to build a RC plane. Because the span is going to be small and the speed relatively low, I estimate the R-number to be around 100,000. Is there an airfoil optimized for that range of Reynold's ...
2
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1answer
3k views

How to calculate variable pitch propeller parameters?

I'm carrying out a project on Variable Pitch Propellers for UAVs and especially self-adjusting or Passive Variable Pitch Propellers that change pitch due to aerodynamic forces and Pitching Moments. ...
2
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1answer
832 views

How does airfoil thickness affect the Mach number at which it experiences transonic flow?

Roskam (book: Airplane Aerodynamics and Performance, Subparagraph: 2.5.2 HIGH-SPEED AIRSPEED INDICATORS (COMPRESSIBLE FLOW)) affirms: [...] Airplane with no sweep and thick airfoils become ...
2
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2answers
174 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(...
2
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1answer
70 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). ...
2
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2answers
139 views

How is rotor airfoil analysis different than fixed wing airfoil analysis?

What the is difference between rotor airfoil analysis and fixed-wing airfoil analysis? Intuitively, it seems that the airspeed at the tip of a rotor blade would be more than that at its root. Wouldn'...
2
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1answer
144 views

Do commercial passenger airplanes have cambered airfoils?

It seems to me that they logically would, since they have no need to fly upside down like an aerobatic plane would (so they would not need a symmetric airfoil for any conceivable reason). That being ...
2
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1answer
216 views

Do Alaskan bush pilots generate a Clmax of 5 with 90° flaps?

I understand the Alaskan bush pilots use 90° flaps in the Valdez STOL competition. I think this would stall the flaps. And if so, it wouldn't increase lift and reduce stall speed, but Javafoil says ...
2
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1answer
254 views

Where is the midspan airfoil located on the 737?

The 737 has a root airfoil, two midspans, and one outboard. Is the midspan located under the fuselage or between root and tip?
2
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1answer
269 views

Shock wave on airfoil

I was wondering the other day, during the trans sonic regime, when the velocity over the airfoil becomes supersonic,why does the shock wave standing on the airfoil moves downstream when the free ...
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1answer
149 views

What is the function of a sweep cable?

This is Goat3 ultralight with sweep cables,what is the fuction of these sweep cables?
2
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2answers
4k views

Why does the stagnation point on airfoil move with the angle of attack?

What is the physical explanation for the reason the stagnation point is where it is? And, why does it move further down the lower side of the airfoil with an increase in angle of attack?
2
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2answers
2k views

What are the effects of camber location in an airfoil?

Am I correct to assume that for a low speed aircraft, the location of the camber in the MAC's airfoil will correspond with the aerodynamic center? Also, does that affect the moment coefficient? And ...
2
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1answer
1k views

What is the mathematical relation between CLmax and Reynolds number?

I know that Reynolds number influences CLmax, but I am not able to find any formula with which I could plot a graph!
2
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1answer
1k views

How does the airfoil pitching moment relate to center of pressure?

I've looked everywhere to find the answer and it's still unclear to me. How does pitching moment relate to center of pressure? Does it relate to coefficient of lift? I have made a carbon fiber wing ...