Questions tagged [airfoil]
The 2D shape of a section of aircraft wing.
270
questions
0
votes
1answer
112 views
How to calculate the takeoff speed for a hypothetical aircraft?
Given some basic information such as:
aircraft weight
wing load (including wingspan, and basically the whole wing configuration)
airfoil profile
coefficient of lift
angle of attack
Is it possible to ...
4
votes
1answer
85 views
Is it possible to have a separated boundary layer without having reversal flow?
To fix the ideas, let's consider an airfoil instead of a generic shape.
As far as I understand, the separation of the boundary layer takes place after there is a region of reversal flow on the suction ...
4
votes
2answers
122 views
Can I assume that aoa on horizontal stabilizers correspond to aoa of the main wing?
I am in the process of designing a small wing (Re ~ 50-100k) and am wondering if given (a) the Cm on the main wing is relatively small at low aoas, (b) the horizontal stabilizer will produce lift as ...
5
votes
1answer
148 views
Does wash-out reduce drag?
I am in the process of designing a small wing (Re ~ 50-100k) and was planning to "un-twist" the tip of the foil by -5°. This corresponds to the 5° aoa where the center part of the wing has ...
1
vote
1answer
121 views
How to turn inviscid data to viscous?
I have used Panel method to calculate Cp vs x/c graph and CL. But as panel method assumes attached flow it does not give an flow separation and thus in CL vs alpha graph I could not find any stall. My ...
0
votes
1answer
123 views
Why aren't HLFC panels mounted on wing?
I watched The Insane Engineering of the 787 by Real Engineering. He just gave short detail about the HLFC(Hybrid Laminar Flow Control) panel and mentioned their purpose isn't available online. I found ...
0
votes
0answers
47 views
What airfoil profile generates the greatest lift force for 0° angle of attack? [duplicate]
The profile is intended to be used as a flap - not as an aircraft wing, so consistent profile shape over the entire span. Is there any particular profile recommended for such use and at low speed air-...
2
votes
2answers
137 views
How do thick and thin airfoils compare in lift generation?
I find myself confused when comparing the lift generation amongst Thick and Thin Airfoils.
A paper to which I have added reference below claims that thin airfoils are better in generating lift because ...
9
votes
1answer
536 views
Why are there two local maximums on some CL vs AOA curves?
I know what a stall is but I don't understand why there are in some cases two local maximums on the $C_L$ vs AOA curve of some airfoils. What is the reason for the mini stall that occurs before the ...
6
votes
1answer
324 views
What is a laminar airfoil and what are their pros and cons?
I am wondering what is a laminar airfoil and what are their advantages and disadvantages if compared to other designs.
0
votes
0answers
58 views
Circulation around an airfoil at negative α
I was recently reading this very helpful string What is the physical meaning of circulation found in Kutta condition? and it explained very nicely potential flow around an airfoil. My question then is ...
0
votes
0answers
64 views
Does the A220-300 use supercritical airfoils in its wing?
I'm curious about whether or not this modern airliner uses supercritical aifoils in its wing, or just conventional NACA-style airfoils.
1
vote
0answers
90 views
What do these terms related to airfoils mean?
I keep coming across some terms related to airfoils and I'm not able to find clear definitions for these terms.
Bubble ramps
pressure recovery
suction side
3
votes
0answers
71 views
Are empennage airfoils always symmetric in conventional airliners?
I'm specifically interested in these models: A319, B737-700, A220, E195-E2. You could call these conventional airliners, so I suppose the question is if these "conventional" planes have only ...
1
vote
0answers
34 views
Wing and horizontal/vertical tailplane airfoil type and relative thickness?
I've been searching for data on the airfoil type (namely if they are supercritical, aft-loading etc.) and relative thickness (average or in different positions) of the empennage (both horizontal and ...
1
vote
1answer
139 views
Servo-actuated aerofoil
I intend on calculating the the servo torque required to actuate a 75mmx38mm NACA0012 airfoil. The example at the end of the page in the link https://github.com/build-week/hover-jet/blob/feature/start-...
1
vote
1answer
66 views
How do i find a supercritical airfoil for my preliminary design?
The following information is available but i don't exactly know where to get the information about SC Airfoils from. Do Airbus , Boeing use secret airfoil that they don't disclose?
Cruise Speed = 240 ...
0
votes
1answer
83 views
What is the relationship between the design lift coefficient and the section lift coefficient of a NACA5 airfoil?
I would like to know the relationship between the design lift coefficient Cli, of a 5-digit NACA airfoil, with the expression Cli = 0.15*L according to Wikipedia. And the section lift coefficient of ...
-2
votes
1answer
313 views
Why doesn't Boeing use supercritical airfoils?
It's my first question & I really want to know the answer from professionals to decide if my new design of airfoil is worth it because the initial test by CFD software (Fluent-ANSYS) indicate that ...
0
votes
0answers
27 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 ...
1
vote
1answer
324 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)....
7
votes
3answers
316 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 ...
0
votes
1answer
143 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 ...
2
votes
1answer
78 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 ...
2
votes
2answers
188 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
votes
1answer
190 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 ...
1
vote
0answers
75 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 ...
0
votes
0answers
69 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 ...
2
votes
1answer
92 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
135 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
1answer
109 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
155 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
495 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
121 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
72 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
271 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
294 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
325 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
116 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
165 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
158 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
204 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
391 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
147 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
64 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 ...
4
votes
2answers
377 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 ...
19
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
203 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 ...