Questions tagged [drag]

Aerodynamic drag is the fluid drag force that acts on any moving solid body in the direction of the fluid freestream flow. Part of the drag is the direct consequence of the wing generating lift.

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7
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2answers
192 views

What is the “compression ratio” of air hitting the nose?

Sorry but I don't know how to accurately phrase this question. I want to know how much compression results from air hitting the nose of an aircraft. I'm interested in the traditional airliners (Mach ...
2
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1answer
54 views

What is the drag optimized wing form for given lift and bending moment?

I am trying to build a passive hydrofoil board. Something like this: I want to use wood and i am coming to the conclusion that i want to optimize drag for a given ...
2
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2answers
90 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 ...
2
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1answer
61 views

How much extra drag does an external HF antenna incur?

As seen in the picture, some older planes have external HF antennas that run from the fuselage to the tail. Have any studies found the wire to be a significant source of drag or is the difference ...
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0answers
38 views

Do open propellers experience pre-entry drag (additive drag) like an engine in nacelle?

Engines in a nacelle experience pre-entry (also called additive) drag. Do unducted propellers experience it too?
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6answers
177 views

Why is a reduction in lift called 'drag'?

Induced drag is high pressure air 'leaking' to the upper part of the wing (low pressure zone) creating a vortex which means the area of the wing tip with the vortex can't create lift. Drag on the ...
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5answers
323 views

Is (L/D)max achieved at a specific speed or AOA?

I'm little bit confused about the (L/D)max. So I've read this blog: https://joeclarksblog.com/?p=4155 and the author shows this graph: So if I understand it ...
2
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1answer
32 views

Which part of the boundary layer(chordwise) contributes most to friction drag? fore? aft? Why?

along the chord of a wing/airfoil section, which portion of it creates the most friction drag through the boundary layer? Is it in the fore section, close to the stagnation point? or the aft section
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1answer
115 views

How does landing gear affect thrust on a light twin-engine airplane?

I'm working on my commercial multiengine rating. And I got this question from my examiner, and I answered: landing gear produces penalty drag, so it decreases thrust. But the examiner says this isn'...
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5answers
201 views

Why does instability in pitch lower trim drag for an aircraft with a tail?

I have a hard time figuring out why a longitudinally unstable aircraft has a lower trim drag. This seems to be a thing especially in fighter aircraft, so does it have to do anything with supersonic ...
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2answers
687 views

Acceleration of a supersonic aircraft after breaking the sound barrier

People on the physics stackexchange recommended I ask here, so I am pasting my question regarding supersonic aircraft. I stumbled upon an interesting plot; in particular, the dependence of wave drag ...
6
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1answer
325 views

Why is a rectangular wing with winglets not better than an elliptical wing?

Why is a simple rectangular wing with winglets not better than an elliptical wing in terms of induced drag and produced lift?
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1answer
86 views

does a semi sphere have more drag in comparison to a flat plane with equal surface area?

What the title says, some things to know is that these aren't solid shapes, think of a bowl and a sheet of wood.
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0answers
78 views

What operational aspects of Alphabet's Wing drone delivery service will be the same as that of an airline?

The NPR News article and podcast FAA Certifies Google's Wing Drone Delivery Company To Operate As An Airline begins with: The Federal Aviation Administration has certified Alphabet's Wing Aviation ...
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2answers
248 views

Why isn't the bell distribution used?

Why has the bell distribution not become widely used? Is the bell distribution only ideal in inviscid flow scenarios or is there another reason for the lack of use?
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1answer
719 views

Is drag coefficient lowest at zero angle of attack?

The drag coefficient of a symmetric airfoil is lowest when its angle of attack is zero. I'm not sure if this is true in general.
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1answer
187 views

Why does a subsonic nacelle inlet have a throat before the diverging section?

Aircraft propulsion 2nd edition by SAEED FAROKHI" p.340 Aircraft propulsion 2nd edition by SAEED FAROKHI" p.123 As we can see from the image, the nacelle slightly converges towards a throat, before ...
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1answer
155 views

What is scrub drag?

I've come across the term "scrub drag" in several papers recently, but can't find a detailed definition of this phenomenon. This is specifically in reference to aircraft and seems to apply to engine ...
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1answer
213 views

What effect does the angle of attack have on lift and drag?

In general, what effect does the angle of attack have on lift and drag? I understand the the B-25 take-off run was normally in excess of 1500 ft, the exact value dependent upon load, density altitude,...
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1answer
232 views

Why does transonic drag happen?

I have heard of transonic speed and it is between supersonic and not supersonic. What is it and why does it happen to aircraft and how does it produce a lot of drag. How do you prevent it from ...
4
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1answer
113 views

How does a weak shock-wave boundary-layer interaction create wave drag (other than through direct shock losses)?

I'm trying to understand the physical cause of wave drag, beyond the simple statement "the presence of shockwaves increases the drag". As far as I understand, in the case of a weak BLSWI (so without ...
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5answers
732 views

Why are the leading edges of wings not always made as 'sharp' as possible?

Why is an airplane's wing (the leading edge) not made as sharp as possible to break the air, in the same way that a ship's hull is made sharp to easily break the water? This is unlike Concorde's nose ...
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2answers
370 views

How does wing aspect ratio influence lift and drag?

I know simmilar questions are all over the internet (and this website too), but there's one thing that i just cannot comprehend and none of the articles i read could explain it properly. According to ...
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0answers
34 views

Determine “basic lift distribution” over a wing that has a circulation distribution

I don't understand what they mean with basic lift distribution. I have calculated C_L which is 5a (a is alpha in radians). I added the relevant equations here.
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2answers
140 views

How do endplates reduce induced drag?

I have heard the explanation which states that the endplates reduce the tip vortex formation thereby reducing induced drag. From what I understand induced drag is the backwards component of the total ...
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2answers
181 views

What is the relationship between drag and sink rate?

I was just brushing up on basic aerodynamics and I have something I want to clarify about flying in the region of reverse command. I went up in my 172 the other day and noticed the following while ...
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0answers
26 views

What is a typical Cd0 value for single-slotted flaps?

I've been having trouble finding any source for what a typical value would be for single-slotted flaps. I haven't been able to find any information within Anderson's Aircraft Performance and Design or ...
2
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1answer
120 views

Does speed or angle of attack generally have the greatest impact on total induced drag?

I know induced drag varies with speed and angle of attack in straight and level flight. Which factor primarily determines the amount of induced drag? The speed of the airfoil through the air, or the ...
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5answers
426 views

How to recognize the horizontal winglet in the Horten design, or the experimental glider in this video?

Comments below the NASA Armstrong Flight Research Center video Proving Prandtl- With A Twist! incclude: This video is entirely a hidden jewel in youtube, it deserves much more attention than ...
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2answers
450 views

What prevents BFS from becoming unstable when pitching from horizontal to vertical?

In this video from (SpaceX's BFS landing) there is a point where the ship tilts from horizontal « belly first » terminal velocity freefall, to vertical « engine first » landing position. The graph ...
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4answers
302 views

How can drag induced by the landing gear be reduced?

What are some of the methods used to reduce the drag caused by the landing gear for aircraft with non-retractable landing gear?
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0answers
186 views

Calculating induced drag approximation using XFoil generated parasitic drag

I am trying to do rough predictions of induced drag using the XFoil results for parasitic drag. To do so, I am using the lifting line equation for induced drag and the Oswald efficiency number: $C_D=...
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1answer
297 views

How to calculate the induced drag coefficient?

In an exercice of Flight mechanic, I have to compute the drag coefficient at zero lift: $C_{D0}$.We saw in class two ways to find it : $$ C_{D0} = \frac{\pi AR e}{4E_{max}^2} $$ With $AR$ the aspect ...
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3answers
510 views

What is compressibility drag?

I don't mean wave drag here. What is compressibility drag, which is understood to be a form of miscellaneous drag?
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3answers
362 views

How can pilots minimize parasite drag?

What can pilots do to minimize parasite drag? As far as I know the effect of parasite drag really depends on the manufacturer of the airplane, but can pilots do anything about it?
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0answers
57 views

Is winglet height equivalent to duct height?

Winglets increase effective wingspan by causing vorticies to be generated further away from the wing root in proportion to the height of the winglet (if vertical), likewise with winglets on propellers....
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1answer
258 views

What is the drag (or $C_D$ vs $C_L$) of the Airbus A320 in cruise flight?

Is there any website or data-sheet that I can find drag of airplane for cruise conditions. $C_D$ vs $C_L$ graph is also acceptable. To be more specific I am searching drag values of A320 in cruise ...
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1answer
125 views

Why do I see moisture coming from the middle of the wing as well as wingtip vortices? [duplicate]

A lot of times I see small tube like streams of visible moisture training from the middle of an airliners wing. I assume this is induced drag created by wingtip vortices, when the aircraft is heavy, ...
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3answers
545 views

Why does a turbulent boundary layer cause more friction drag than a laminar boundary layer?

From what I understand, friction is caused by viscosity and a bigger Reynolds number signifies lower viscosity. Thus, a higher Reynolds number(i.e. turbulent flow) results in lower friction. But, ...
39
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3answers
8k views

How is it possible for supersonic aircraft to push air out of the way?

If the force (pressure) can be transferred/propagated only at the speed of sound, how are supersonic aircraft able to move air out of their way/do work on the air? It seems that they must transfer the ...
2
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1answer
285 views

How can one approximately guesstimate wave drag?

Wave drag is an especially high drag that affects supersonic vehicles above mach 1, but I've found it hard to find source materials to estimate wave drag. I'm looking at the transonic region till Mach ...
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2answers
245 views

What are the two turning tendencies that occur during a steep turn?

A question has come up in preparation for a Block exam. what are the two turning tendencies that occur during steep turn? If you know this may you please explain to me, why these tendencies occur. ...
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1answer
168 views

Lift and Drag Coefficients using load cell data

I have a MAV and I need to find out the lift and drag coefficients for the wing and tail. I am not available with a wind tunnel so I will be using a load cell along with a separate wind source. Now I ...
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0answers
451 views

Why don't more airplanes incorporate spiroid winglets? [duplicate]

In typical airplanes, lift induced drag can account for the majority of the overall drag. Why don't more aircraft employ methods to reduce this and specifically why not spiroid winglets? From every ...
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1answer
428 views

How does drag change with Reynolds number?

If you want to scale down an airframe, i.e., for wind tunnel testing, you have to adjust for the Reynolds number. I want to ask if in case I forgot to adjust the Reynolds number, would the drag on the ...
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6answers
3k views

Is lift in fact a kind of drag?

Given the similarities between Lift and drag and their very similar relationships to the density, surface area, and airflow velocity, could one, in theory, describe aerodynamic lift as a kind of drag ...
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1answer
85 views

Is aspect ratio efficiency related to the momentum added to the air?

Many years ago I was taught that for generating lift or propulsion, lower losses were associated with imparting less momentum change to a larger volume of air, and higher losses were seen when ...
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3answers
267 views

Is it possible to eliminate induced drag completely?

According to Wikipedia an airfoil of infinite length would create zero induced drag. Therefore, would it be possible to make a wing that creates no drag if you ignore viscous effects (skin friction) ...
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5answers
8k views

Why, until recently, were smooth nose sections not popular?

Why, until recently, were smooth nose sections not popular? By smooth I mean without a break between the nose and windshield. (The question focuses on airliners.) Seeing the Starliner (left) and DC-7 ...
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2answers
275 views

How significant is the lift induced drag contribution to total drag of aircraft at cruise speed?

How significant is the lift induced drag contribution to total drag of aircraft at cruise speed? From what I've learned so far it seems to be around 10 to 15 percent of total drag. I suspect the ratio ...