Questions tagged [airfoil]
The 2D shape of a section of aircraft wing.
245
questions
2
votes
1answer
47 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). ...
3
votes
1answer
81 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 ...
2
votes
0answers
31 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. ...
9
votes
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 ...
1
vote
1answer
72 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 ...
1
vote
1answer
113 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. ...
1
vote
2answers
88 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 ...
0
votes
1answer
48 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 ...
2
votes
1answer
123 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
votes
1answer
238 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 ...
0
votes
1answer
134 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 ...
3
votes
1answer
99 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 ...
1
vote
1answer
99 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 ...
1
vote
1answer
77 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/$...
0
votes
1answer
185 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 ...
1
vote
4answers
255 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 ...
1
vote
1answer
130 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 ...
13
votes
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 ...
0
votes
1answer
51 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 ...
3
votes
2answers
212 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 ...
18
votes
1answer
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) ...
-4
votes
3answers
196 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 ...
2
votes
3answers
438 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
votes
1answer
78 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 ...
1
vote
1answer
66 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: $0.25c$, $...
1
vote
1answer
55 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?
0
votes
1answer
85 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 ...
4
votes
2answers
437 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 ...
-2
votes
2answers
182 views
In the context of aircraft design, what are the differences between a flat plate shaped airfoil and a droplet shaped airfoil? [closed]
I am relatively new to aerodynamics and am curious to know what difference it makes on an aircraft - lift, drag, weight etc - which of the two airfoils is used on the wing.
1
vote
1answer
127 views
How does vorticity change the lift coefficient of an airfoil?
For airfoils in unsteady motion, the lift coefficient oscillates and the wake is characterized by vortex shedding.
How does vortex shedding affect the lift coefficient for an airfoil?
2
votes
1answer
69 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 ...
0
votes
0answers
50 views
How can we find maximum lift coefficient of Airfoil?
I am trying to find the maximum Lift coefficient for airfoil NACA 64A-404. I chose this airfoil for wing. I am stuck at finding the Clmax. I tried to use javafoil but javafoil is showing Cl less than ...
0
votes
1answer
191 views
Does thin airfoil theory work at very high angles of attack?
Thin airfoil theory says that lift coefficient is directly proportional to the angle of attack in radians. I haven't been able to find any limit, short of stall, for applying this theory. It would ...
1
vote
1answer
445 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 ...
3
votes
2answers
181 views
Are larger airplanes more likely to stall?
Stalls happen when the boundary layer on top of a wing slows so much that it essentially becomes part of the airfoil.
My question is, as the wings on larger aircraft present a longer flow path for ...
0
votes
1answer
43 views
Is the ratio of HP to weight constant for identical air frames of different sizes? (See Scenario)
In my head it seems logical that there would be a proportion between engine HP and empty weight. For example, the Wright Flyer weighed around 600 LBS empty and had a 12 HP engine. If I were to make an ...
1
vote
0answers
28 views
What happens to the dynamic temperature in the boundary layer at supersonic speed?
In the boundary layer for a supersonic flow, does the dynamic temp decrease?
Thank you
1
vote
1answer
76 views
How to calculate pressure distribution over an airfoil from its coordinates?
I need to compute the pressure distribution over an airfoil (I have the coordinates, but any will do) with the streamline curvature method. Unfortunately, I cannot find much on the web.
Can someone ...
5
votes
1answer
94 views
Why the gradient of $C_L$-$\alpha$ graph increases with the Mach number?
From the JAA ATPL Book 13 (Principles of flight) the gradient $\frac{dC_L}{d\alpha}$ of the $C_L$-$\alpha$ graph increases for higher Mach numbers. Can someone explain why this is the case?
1
vote
1answer
114 views
How to reproduce NASA/Langley airfoils for general aviation with long chord lengths?
I have scaled a NASA/Langley LS(1)-0413 airfoil to a 90 inch chord length, and now the trailing edge is 0.5in. Any longer chord length would have a larger trailing edge thickness.
(90in*(0.0071-0....
2
votes
2answers
97 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'...
6
votes
1answer
476 views
Why is the pitching moment of this symmetric aerofoil non-zero?
As I understand it, the pitching moment coefficient of a symmetric aerofoil should be zero, under potential flow assumptions. Obviously, approaching stall and post-stall, these assumptions are invalid ...
0
votes
0answers
91 views
How to calculate the mass moment of inertia of a symmetric wing like NACA-0012?
I am working on the pitching mechanism of a NACA-0012 wing. I have the mass and found out the centre of mass of the wing but the software (OpenFOAM) needs more parameters such as the mass moment of ...
2
votes
1answer
426 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.
4
votes
2answers
2k views
Why are highly cambered airfoils rarely used in propellers or wings?
Highly cambered airfoils like the Seligs and Epplers are hardly ever used in propeller or wing sections. Why?
Does their performance reduce at high Re? Are they only adequate at low Mach, low Re?
...
0
votes
2answers
376 views
How to increase payload capacity of plane?
Keeping thrust, wing span, weight (of plane) constant, can we increase the payload capacity (nearly 50% more)? Adding payload to plane, it decreases thrust/weight ratio, how does it affect the control ...
0
votes
5answers
214 views
Can lift be increased by increasing the angle of incidence of the wing? [closed]
Can the lift of a plane be increased by increasing the Angle of Incidence (angle between the chord line of the main wing and the axis of the fuselage)? Meaning, can more lift be generated while the ...
3
votes
2answers
889 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 ?
0
votes
1answer
165 views
Why do intermeshing helicopters use asymmetric airfoils?
I am referring to the Kaman K-max and the Kaman Huskie here. They both use NACA 23012, which is an asymmetric airfoil. Any reason as to why this is? Is there a different mechanic in play when ...
0
votes
0answers
53 views
How to choose airfoil for High Subsonic small UAV?
I am trying to make a concept for a small UAV. The UAV shall be flying at Mach=0.75 , shortly 0.9
For this, I am looking for an adequate airfoil, which allows me, to avoid Mach=1 on the airfoil. From ...
