# 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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### What resistance is offered by an appendage on an aircraft flying at 30,000ft at 200 mph?

What formula can I use for calculating the resistance offered by an appendage above an aircraft wing? The appendage has a surface area of 10 square meters, positioned at an angle of 45 degrees. The ...
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### 2D vs 3D Pressure Drag

What is the difference between the parallel component of the drag that depends on alpha for a 2D airfoil and the parallel component of the drag that's on a finite wing? I understand that for a wing ...
148 views

### Does dynamic stability decrease with airspeed

Context: I am writing my thesis on the topic of satellite drag reduction by the means of near-specular surface scattering. The theme touches aerodynamics in some sense, but the physics are honestly ...
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### What is the supersonic L/D of subsonic jetliner

Suppose you somehow managed to accelerate a typical jetliner oastbthe sound barrier and to whatever speed you wanted, climbing to keep lift constant. Is there any data on his the L/D evolves with Mach ...
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### How does a thickening boundary layer create form drag?

Imagine a normal wing with flow over it, and to simplify things it's at 0 AoA. Drag is being made mainly because of form drag and skin friction drag. I'm not sure on this, but I don't think there ...
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### wave drag: Lift coefficient in Korn's Equation

I have been using the Korn equation: $$M_c = \frac{0.95}{cos(\lambda)}-\frac{t/c}{cos(\lambda)^2}-\frac{C_L}{10cos(\lambda)^3}-\sqrt[3]{\frac{0.1}{80}}$$ to estimate the critical mach number of a ...
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### In a straight and level flight if thrust is equal to drag how is aircraft moving forward?

If two forces are equal and acting in opposite direction should not the object remain stationary. Is there an excess thrust which actually pushes the aircraft forward ?
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### Can there be interference drag in inviscid flow?

I understand that interference drag is the difference between the terms: the total drag of a configuration, and the sum of the individual drags of the components in the configuration. (It exists due ...
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### How does the lift-to-drag ratio depend on absolute sizes?

A dependency is provided here $$(L/D)_{\max} = \frac{1}{2} \sqrt{\frac{\pi \varepsilon ~ \mathrm{AR}}{C_{D,0}}}$$ AR significantly affects the outcome in this dependency. AR varies significantly among ...
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### Range, Endurance and Fuel Cost Savings of an Aircraft

I have recently carried out CFD simulations on the A320 fuselage and modified its fuselage. I did this by matching the Reynold's number of the cruising altitude. The reference values were taken at ...
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### Determining Sectional Drag Coefficient Using Propeller Geometry

Im trying to teach myself blade element theory for helicopters and propellers, but im getting quite confused. Most of the papers and textbooks I read will reach an equation for differential thrust ...
1 vote
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### Is induced drag only created by wingtip vortices induced downwash?

In PHAK, I saw that There is two types of downwash formed by airfoil shape that necessary(help?) to produce lift formed by wingtip vortices in phak 5-7 It said 'This induced downwash has nothing in ...
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### In which position does Starship wings produce the most drag?

I was watching the video from a few years ago where SN15 did the flip manoeuvre and landing. The actuated fins (lower flaps) can help Starship to pitch while during its descent. However, I am ...
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### Why does turbulence over a wing make drag?

Drag is the result of air ‘pushing’ the opposite direction of flight, if you want to think of it that way. The skin friction drag is made from the air trying to pull the wing opposite of the flight ...
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### Why is a half-streamlined body less aerodynamic?

As seen here, a streamlined half body is less aerodynamic than a fully streamlined body. The half streamlined one has less surface area (kind of) and less frontal area. Why is its drag more?
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### Minimum sink speed and maximum endurance speed

For a given airplane, are the minimum sink speed and maximum endurance speed the same? Thankyou
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### What are the differences between an oblique wing and a swing wing? [duplicate]

How they differ from each other. How do they work. What is the structural differences. How do they help in reaching mach speeds and get better fuel efficiency. How does they both perform with max ...
1 vote
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### How much of the Virgin GlobalFlyer's L/D is due to laminar flow?

Despite travelling much faster than the Voyager, it has a significantly higher L/D. The latter seems to have two features that disrupt laminate flow, that are absent in the former. Namely the canards ...
1 vote
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### Drag breakdown of a typical civil airplane wing

How much of the drag produced by a typical GA/airliner/cargo plane's wing at cruise is induced, frictional, and pressure drag?
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### Thrust needed to overcome parasite drag that increases with speed

Can anyone explain this passage from page 11-5 of the PHAK: “ For example, if an aircraft in a steady flight condition at 100 knots is then accelerated to 200 knots, the parasite drag becomes four ...
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### What type of probe can measure induced drag in the wake?

Induced drag can be measured from velocity preturbation in Treffz plane. In Treffz plane what velocity direction is important for induced drag, vertically down, lateral(horizontal, "spanwise&...
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### Does this comment thread incorrectly conflate glide ratio with lift-to-drag? [duplicate]

In the comments on niels nielsen's answer to "Why are no recent small aircraft designed to be 'characteristically incapable of spinning' as the Ercoupe was?," John K commented, "[The ...
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1 vote
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### Can I reduce drag with channeling freestream air at the backward facing surface?

Idea is to increase static pressure at backward facing surface to reduce drag. Can I reduce drag with channeling freestream air at the backward facing surface, like picture suggest?
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### Why induced drag shows up as reduced pressure downstream of the wing?

Quote from book (Understanding Aerodynamics: Arguing from the Real Physics, Doug Mclean): "When we look at the force/momentum balance, the induced drag shows up in the flowfield primarily as ...
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### Are there studies to find surface treatments to reduce the drag of an airfoil?

I know that by designing an airplane or a car close to a teardrop, we can reduce the drag. My question has to do with the surface friction treatment. Some torpedoes glide in water more efficiently ...
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### What are the effects of wing washout and anhedral on induced drag?

I am studying for my ATPL and was curious if and how induced drag varies based on wing anhedral and geometric washout. I have a basic understanding that spanwise flow affects induced drag since there'...
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### How does drag change efficient cruise conditions?

If I have an aircraft, and I reduce the induced drag produced by it, does this mean I should operate it at a higher altitude and faster speed to take advantage of the drop in total drag, or slower at ...
1 vote
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### How to calculate lift and drag coefficients of an airfoil with slotted flaps?

I am doing a project attempting to determine the increase in lift and drag coefficients of an airfoil as the angle of its flap increases. In my research, I have found the thin airfoil with flap ...
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### Cause of Drag From Windmilling

I know that when a propeller is windmilling it creates drag, I assume this is from the propeller being flat against the air causes drag, but propellers are designed to essentially pull an airplane ...
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### Forces acting on ram air parachute (for pulling ships)

I recently stumpled across this question about the ram-air parachutes for use in pulling ships. In this answer it is stated that the parachute needs to travel perpendicularly to the ship's motion in ...
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### Does the cross-sectional shape of a fuselage affect drag?

Comparing two bodies with the same streamlined longitudinal shape, and the same cross-sectional area, one with a circular cross-sectional shape, the other with a quadratic cross-sectional shape, ...
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### Does CG change airspeed in a descent or glide?

If the CG of an airplane moves forward, would it fly a faster or slower airspeed in a descent? Usually during a descent or landing, you'd use pitch to change airspeed and power to control descent rate....
1 vote
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### Reference Area of Airfoils

Airfoiltools.com shows a higher Lift/Drag coefficient for thick symmetrical foils than for thin symmetrical airfoils. Is this because the higher drag coefficient of those airfoils is hidden in the ...
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### Determining optimum area of parafoil, and then drag

I am designing a parafoil recovery system for a small payload of 300x100x500mm (2.4kg). I have chosen an Aspect Ratio of 3, and from a NASA wind tunnel test report, the coefficient of lift and drag is ...
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### What is viscous induced drag?

In this video he talk at 17:04 about viscous inudced drag, induced drag comes exclusively from inviscid theory,by the definition this drag exist only in inviscid world, so what is viscous induced ...
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### Has resultant pressure vector backward component at 2D airfoil in viscid flow?

When we integrate static pressure around 2D airfoil that produce lift(viscid flow), has resultant pressure vector backward component? I think pressure vector will point slighlty back, so it has some ...
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### Why total drag formula include drag at zero lift?

Total drag = Do + DL Why total drag include drag at zero lift if we are interested at drag when wing produce lift? We cant assume that friciton and particularly pressure drag at zero lift AoA dont ...
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### Does induced drag drop when wing is stalled?

From formula, induced drag is function of lift. When wing stalls, lift is reduced so induced drag must also be reduced? Stall decrease static pressure at suction side of wing, so I know pressure drag ...
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### What technical features account for the P-51B/D's low drag relative to other fighters of the day (e.g, Spitfire Mk IX)?

I am really sorry to dredge a popular topic up again. Unfortunately, after reading through some papers on the P-51 as well as all the past forum threads I could find on this topic, I have found myself ...
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### How to approximate the drag for rectangular vertical flat panel placed along the wind and inclined?

So on the top is the view from the top, below it is the side view. If the angle is zero it is similar to simple flat airfoil. So I calculated the Cl and Cd in xfoil and got the Cl = 0 and Cd = 0.02398 ...
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### Induced drag vs parasite drag understanding

I am having the following graphic from one of the question for the EASA PPL(A) exam. While I know that: (1) represents "induced drag", as its decreasing with higher speed (2) represents &...
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### Does the 787 vertical stabilizer have a connection fairing?

In general, a vertical stabilizer connected with the fuselage will form junctions. The junctions trigger a mix of airstreams, and causes interference drag. A fairing is used the ease the sharp ...
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### Why is icing more critical on smaller airplanes?

My professor mentioned that the contour of smaller airplanes changes more drastically than that of larger airplanes. In this context, he mentions the surface-to-volume ratio. But how does that relate ...
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### What is the most efficient way to reduce interference drag when surface imperfections are unavoidable?

Interference drag can start to appear when there’s imperfections or excrescences on an aircraft outer surface. For example the following image shows some of these typical imperfections: Source of ...
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### Landing gear drag and weight calculations

I have read numerous books and researches, but I couldn’t find any formulae that actually work for how to calculate the following (for commercial aircrafts): 1- Drag coefficient for a retractable ...
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### Is there a formula for calculating drag coefficient based on the 4 digit NACA airfoil?

Are there any existing formulas that can be used, or maybe some methods to derive an equation that can calculate the drag coefficient based on the NACA airfoil?
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### How is blended winglet better?

*Make sure to read the following as I cannot explain my question in one sentence Winglets are a kind of wingtip device that is installed on an aircraft to reduce drag and improve fuel efficiency. ...
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### Explaing lift tilt back in induce drag pictures?

This is usual induced drag diagram. What is black vector in diagram below? If it is lift you cant decompose lift in lift(L in diagram) and induced drag (Di), this you can do only if this is resultant ...
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### Does induced drag of wing change with speed for fixed AoA?

In wind tunnel we put 3D wing at fixed AoA, then tested at two different subsonic airspeed. At higher speed, wing will produce more lift and more overall drag. Will induced drag also rise at higher ...
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