Questions tagged [aerodynamics]

Aerodynamics is the study of how air moves and interacts with solid objects. It is an essential part of aircraft design.

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Carpet Plots for Aircraft Sizing

Generally, Carpet Plots are constructed to find out an optimal design which will satisfy all the performance needs and is least in weight & cost. I want to know how to construct a carpet plot? I ...
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At which angle tiltrotor's rotors generates more lift?

[Tiltrotor 1] [Tiltrotor 2] I can't name these tiltrotors. I just want to know which of the tiltrotors generate more lift considering aerodynamics and based upon the rotors ...
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How did the pilots of Alaska Airlines Flight 261 stall when they were in a lot dive? [duplicate]

At 16:09:31 one of the pilots said “you’re stalled” This photo says the initial dive started at 16:09:20, 11 seconds before the pilot said “you’re stalled” This brings me to my question: How do ...
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Can transition on an airfoil occur without prior separation?

i.e. can transition occur without the presence of a laminar separation bubble? If yes, what would this look like in a pressure distribution? Here, a clear laminar separation bubble can be seen. The ...
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When is lift greater than weight? [duplicate]

I am wondering in which phases of flight or manouevres lift is greater than weight. I know that this happens during turns and when affected by gusts but when else? During steady level flight lift ...
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Elliptical wing planform and elliptical lift distribution

I know that there are similar topics already here, but after reading them I still do not understand everything. From what I know elliptical lift distribution gives the least amount of induced drag. ...
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Matlab code for Multhopp/Lifting Line methods

I'm part of a new SAE Aerodesign Team and i'm searching for a way to obtain the CL and CD coefficients of a finite wing in subsonic speed. I've tried some codes of Multhopp and Lifting Line Theory, ...
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Cruise Mach Number less or more than Critical Mach Number

Do commercial airplanes cruise at Mach number higher than the critical Mach number? And what is the critical Mach number of airplanes like B777 or A330?
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During which phase of the mission profile, the airplane fastest?

In a mission profile, there are various phases such as Climb, Cruise, and Descent (excluding other phases). My question is during which of these phases, the Mach number of the airplane is highest? Is ...
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Is there any bibliography for triplane aircraft design?

I've been tasked with designing an RC aircraft that has the greatest lift force for a specified wingspan, total length and takeoff velocity, and thus have been studying the different wing ...
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How does Propeller windmilling work?

I’ve got a problem with understanding propeller windmilling. What I know is that when rpm are low and tas is high the blade aoa goes „over” the blade and is some kind of negative now, producing thrust ...
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Does downwash increase or reduce lift generation?

I’m wondering about the impact of downwash on lift generation. I've read that, because downwash creates lift according to Newton's third law of motion, increases in downwash due to greater AoA (...
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Where can I find wind tunnel pressure data for various airfoils?

I'm working on a simple panel method solver based on thin airfoil theory and I would like to validate my code using wind tunnel data. Is there any place where I can find pressure distribution data ...
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What is the effect of wing flex on wing's airfoil shape and its performance effect on wing?

There are good amount of discussion on wing flex in this forum. I am more interested in understanding the effect of flex on aerofoil shape of the wing and its impact on flight performance. Do ...
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Could an airliner be as efficient lower and slower?

Could an airliner ever be as efficient at 15 or so meters using ground effect as it is at 50,000 km even if it has to go slower and be shaped differently?
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Why do modern aircraft tend to have angular tails?

In the WWII-era and earlier, many (most?) planes had rounded tails, even high-speed and high-performance fighters such as the Bf 109 K, Ta 152 (though it is more square-ish), P-38, Hawker Typhoon, and ...
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For an aircraft, what are the differences between nonlinear and linear equations of motion?

So, as far as I understand, linearized equations of motion are just nonlinear equations of motion converted to linear EoM's using approximations and assumptions to simplify/remove elements from the ...
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What's the benefit of cranked wing for commercial airplanes [duplicate]

Many commercial airplanes have a kink in the wing geometry. A discontinuous change in the wing trailing edge sweep is present in the wing of the A320. What's the benefit of this? Is there any ...
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Formula/ Rule of Thumb to determine gap and overlap of a slotted flap?

How to determine gap and overlap of a slotted junkers flap? Zenith boasts a Clmax of 3.4 with slotted flaps and leading edge slats, about 2.8 without the slats. Ballparking the drawing from Zenith ...
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Visualising downwash over a finite wing

The downwash is caused due to higher pressure below the wing than above it (for a positive lift generating wing that is). What I am not able to understand is how would the flow be in a gross sense? ...
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Double deck vs wide body airliner, why would anyone build a double deck one?

I don't understand why double deck aircraft (or multiple decks in general) are a good idea. They must be, because there is a significant amount of them. But given a cross area, which should roughly ...
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Airfoil and Wing Analysis for Transonic Speed (M = 0.85 and Re = 42 million)

I am working on a project where I have to design a plane which has to cruise at 0.85 Mach at 35,000 ft. While working on the wing design, I quickly discovered that 6 series airfoils, with a good ...
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Cascading Wings: Do they really increase lift by 300%?

Cascading Wings for Ultralights: Do they really increase lift by 333%?!?!? The classic NACA 650-18 airfoil has a Clmax of 1.5 according to airfoiltools.com ( a modified 650-18 is used on the Zenith ...
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Air masses, Air flow and changes in direction and intensity

I have a question regarding the airflow an aircraft experiences during 3 distinct scenarios: An aircraft during landing, experiencing a sudden gust of 40 knots from the tail. What would be the ...
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Can aerodynamic forces move the stabilizer by itself? [duplicate]

So if a plane is accelerating with nose down trim, and the electric trim motors are turned off by the crew, can the aerodynamic forces move the stabilizer and make the situation worse?
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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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Does an instrument exist to measure the different types of drag?

Does a 'drag meter' exist that separately shows total, induced and parasite drag? If it doesn't, and in theory, would it be possible to build one?
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Finding Angle of Attack/Angle of Sideslip using East/North/Up Coordinates

I've got a set of data that includes: x rate, y rate, z rate (all ENU) which I'll call xd, yd, zd. roll, pitch, yaw (which I'll call ϕ, θ, ψ) roll rates, pitch rates, yaw rates I'm looking at some ...
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Turbulent flows over 6 series airfoils

6 Series Airfoils were developed to enhance the laminar flow region over the airfoil. But, the Reynolds number at which planes fly are high for the flow to be Laminar. Then what's point of introducing ...
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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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If the Concorde had an engine fail at cruise altitude, would they enter the coffin corner?

I know the coffin corner is only meant for subsonic aircraft, but if the Concorde is just cruising at Mach 1 and had an engine failure and also lost that afterburner, would it enter a coffin corner ...
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The F 18 Hornet and Mig29 ailerons from the external parts of the wings go up some degrees in flight .Why?

In some parts of the flying envelope of the F 18 Hornet and Mig29 the ailerons from the external parts of the wings go up in sync . They're made to go one up one down in order to get rolls,not ...
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When calculating the lift coefficient, what area is used?

Lets say I had this rectangular double curve wing. Orange represents the chord length, red represents the airfoil outline length below the chord line, green represents the airfoil outline length above ...
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How can best glide speed be lower than best rate of climb speed?

I was looking up V-speeds for C172. I don't have easy access to an official copy of the POH, but online I found: $V_y$, best rate of climb speed (at sea level): 76 KIAS (p22) $V_{glide}$, maximum ...
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New Research: VGs increase lift to drag ratio up to 880%. Does it work for flaps too?

Aerodynamic Free Lunch: VGs increase L/D ratio up to 880%. Does it work for flaps too? I understand this research was for a wing without flaps. I understand this reduction in drag with VGs works ...
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If the modern airliner was redesigned from scratch, would it look functionally different? [duplicate]

If the modern airliner (Boeing/Airbus) was redesigned from scratch today without any need for "backward compatibility", would it look functionally different from the current design? And if so, what ...
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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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Position of Engines [duplicate]

Some aircraft ms have their engines located with wings (airbus 320) while some behind wings( embraer erj) . What factors decide this positioning and how does engine position effect flying ...
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How does a delta wing deal with supersonic boundary separation?

The question Why most of the supersonic or fighter aircraft use all-moving control surfaces? emphasis the importance of all moving stabilator for supersonic aircraft. Many supersonic aircrafts ...
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The principle in 'Trompe' is applied to airplanes?

'Trompe' (see Wikipedia) is a water-powered air compressor, commonly used before the advent of the electric-powered compressor. A trompe is somewhat like an airlift pump working in reverse, used to ...
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What is the physical-based/theoretical reason why supersonic area ruling works?

Supersonic area ruling is used to reduce the drag rise that occurs as aircraft pass through the transonic regime. While it has been validated experimentally, what is the theoretical/physics-based ...
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What are the limits of ground effect over water on an airliner plane at cruising speeds? [duplicate]

What height over a fixed plain (such as water) can a plane begin to take advantage of the ground effect or when air is compressed between the wing and ground near cruizing speed? Could an airliner ...
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Does airspeed come into play with vertical speed, in terms of who will reach the ground first?

So let’s say there’s two aircraft, which are the same, and both are cruising at 28,000FT, the only difference is one plane is doing 260 knots and the other is doing 280 knots. If they both pitched ...
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Aerodynamics of Flight Control Surfaces

From what it appears to me, flight control surfaces seem to be taken for granted. In terms of how they actually work and what kind of physical outputs they give in terms of forces and such. Take for ...
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Why does Lift and Drag calculation over an airfoil ignore shear stress?

why in Lift and Drag calculation over an airfoil we ignore shear stress effect and focus on pressure distribution?
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If props throw air outwards, why do some prop diagrams show a reduction in airstream diameter behind the prop disc?

If props throw air outwards, why do some prop diagrams show a reduction in airstream diameter behind the prop disc, or are these velocity vectors? Diagram showing airflow outwards as shown on nap.edu ...
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Zenith-Add horsepower, NASA-add drag: to create lift. How is this possible?

Available horsepower and adding drag to an airplane both create extra lift? How is that possible? Available Horsepower According to the Zenith, available horsepower not used to overcome form drag ...
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How does distributed propulsion work in a pusher configuration?

How does distributed propulsion work in a pusher configuration? In a tractor configuration, the wing benefits from a portion of the prop wash flowing over the wing and producing extra lift ( I stand ...
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Would a 2nd row of distributed props on a 2nd staggered wing of a biplane increase its efficiency?

Would a 2nd row of distributed props on the rearward wing of a biplane with 25% gap and 150% negative stagger increase the efficiency of a biplane ULTRALIGHT, 25MPH, Re 500K? ( rear wing is 25% lower ...
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How do dummy bombs simulate real bombs in training when they're so much smaller?

This picture shows a couple of Mk-76 25lb (11kg) Inert Training Bombs on a McDonnell Douglas AV-8B Harrier II; it's clear that the physical characteristics of the dummy bomb are quite different to ...

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