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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76 views

Do horizontal stabilizers on airliners have varying angle of incidence in the span-wise direction (washout or negative twist)?

Reading this question and answers, I was wondering if modern airliners with cruciform tail have some noticalbe washout or negative twist along the horizontal stabilizer's span. During cruise, if wing'...
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Is it possible to create Interference Drag without physical surfaces conjoining?

Interference Drag is when boundary layers mix/combine, usually it's caused by pieces of metal conjoining (wing struts/gear retracting). Is it possible for interference drag to be created without ...
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Why are crop dusting spray booms not integrated into the wing?

All crop dusting aircraft seem to have an externally mounted spray boom for distributing their pesticides, I imagine this significantly increases drag & therefor performance. What gives? why not ...
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How do you calculate Profile Drag?

second year aeronautical engineering student here. I'm doing some aerodynamics coursework but have run into a problem. I've read through the answers to the question "what is profile drag?" but ...
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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 ...
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How close is the air resistance or drag force to being proportional to the airspeed squared?

How is the total air resistance force exerted upon a body (aircraft or car) related to its speed relative to air at far away? A simple Newton's force momentum analysis suggests that the force $F \...
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Why does adverse yaw exist?

Why does the aileron deflected upwards, thereby reducing lift, not also reduce drag on that side?
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Why is wave drag non-zero for a flow without shockwaves?

Wave drag is often defined as the component of drag that arises due to the presence of shockwaves. Shocks result in an entropy rise and a corresponding increase in drag. However, when using Supersonic ...
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What are the contributors of lift-dependent drag?

If someone wants to plot the drag polar of an aircraft, we have $$ C_D = C_{D,o} + C_{D,i} $$ form/skin drag plus the induced. However, as I feel, form drag and probably skin friction drag (...
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Why don't smaller powered airplanes have better lift-to-drag ratios?

Many airliners have LDRs near 20, and it sounds like the electric Eviation Alice may have an LDR of 24 at 240 kts, but many small planes typically have LDRs of only 8-10. It seems like they could ...
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What is the power curve [closed]

Someone help me understand this thing in a simple way. I understand it helps determine Vx.
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How do you calculate coefficient of drag at an angle?

I am trying to make a simple 2d drag simulator for an object in freefall with an x and y component of wind. If I knew the coefficient of drag on the bottom and side of the object could I use theta to ...
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How much of an airplane's forward energy is lost to lift?

An airplane needs to move forward to generate lift, and because energy isn't created from nothing, all the kinetic energy of lift comes in the form of drag, where air (air resistance) turns forward ...
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Why is a blunt trailing edge a better stabilizer at hypersonic speeds?

Here is what I read about the X-15 spaceplane: The X-15 had a thick wedge tail to enable it to fly in a steady manner at hypersonic speeds.[14] This produced a significant amount of drag at lower ...
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Do the drag force (D) and the drag coefficient (Cd) vary with altitude? [duplicate]

And also how is it related to Reynolds number? Image source Edit: Consider two airplanes, one flying at sea level and the other at altitude and both are at the same angle of attack and true airspeed....
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Why do wings prefer laminar flow if cd is lower for turbulent flows?

Can anyone please explain to me why we prefer to maintain laminar flow over wings, despite the fact that the overall coefficient of drag appears to reduce as the Reynolds Number increases? I have read ...
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In the Cl vs Cd graph, Why the drag coefficient decreases initially with the small increment in lift coefficient?

Cd = Cdo + KCl2 Total drag = Parasite drag + Induced drag When Cl = 0 , Cd = Cdo Increasing in Cl introduces another component of drag (Induced Drag) and therefore the total drag Cd should be ...
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what is the physical explanation for additive drag?

from what i understand, additive drag is not really drag. it is a way to account for the variation of inlet condition due to conservation of mass. but i still don't get why it create drag(negative ...
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How is the total drag variation with velocity related to altitude?

Here in the question given I am confused how to relate the altitude with the given plot of total drag and velocity.
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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 ...
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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 ...
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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 ...
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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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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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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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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 ...
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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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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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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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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 ...
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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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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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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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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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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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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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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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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 ...
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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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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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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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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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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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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 ...
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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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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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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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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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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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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?