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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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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129 views

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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108 views

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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158 views

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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What determines the direction of rotation for counter-rotating propellers?

As Wikipedia and other sources make clear, most twins with counter-rotating props are configured with the left (#1) prop turning clockwise (as viewed from behind the plane) and the right (#2) prop ...
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Is there any benefit to sweep back on an ultralight?

Is there any benefit to sweep back on an ultralight of: 15 deg 30 deg 45 deg. other?
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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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Is it true pilots in a smaller aircraft have the option of using the right or left door as rudder, to offset the actual rudder if failed? [duplicate]

So if the rudder fails or gets stuck in the “left” position a pilot could open the right door and it would essentially counter the effect?
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Do the F-16's leading edge flaps lock up at +2° when the aircraft as a whole is supersonic, or when the airflow over its wings is supersonic?

My question is: do the leading edge flaps lock upright when the aircraft as a whole is supersonic, or when airflow over wings of the aircraft is supersonic?
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How can Lift = Weight; if airliners fly with Thrust-to-Weight ratios = 0.3? [duplicate]

Question: I'd appreciate it a lot if anyone could explain how the wings can generate lift that is 3.3x more than engine thrust? Is there any experimental proof that this? Or is the assumption that ...
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Is lowering V1/VR (and runway length required) the only reason for flaps at take off?

I've read that some aircraft (examples include the Saab 340 and the Fokker 100) can perform flapless take offs, provided there is enough runway available. It's also my understanding that, in terms of ...
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What is the minimum speed a glider can thermal at?

What is the minimum speed a glider can thermal (climb)at, typically, in terms of Vs over a dark field on a warm summer day? Is it 1.1Vs, 1.2Vs, or 1.3Vs, etc,?
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Would a slotted flap still work if the prop is located mid wing between the wing and flap?

Would a slotted flap still work if the prop is located in a slot mid wing between the wing and flap? This would be for a distributed propulsion application for an multi prop ultralight triplane, ...
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What is the minimum glide ratio of a motorized glider?

What is the minimum glide ratio of a motorized glider, enough to climb in typical summer afternoon thermals over a dark field or similar? In other words, at what minimum glide ratio would a glider be ...
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From Aerodynamic view, what is the advantage/disadvantage of the Akagi Kaman K-Max Helicopter?

Here is a video showing the helicopter, the rotors are perfectly synchronized. As there are not many such design helicopter, then my question are, is any aerodynamic weakness? What is its advantage/...
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What is the best prop location for distributed propulsion - pusher, tractor or blown flap for an ultralight?

What is the best prop location for distributed propulsion - pusher, tractor or mid top wing ( blown flap) for an ultralight, max speed about 60mph, for MINIMUM takeoff distance ( 20-40') and about ...
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Can prop exit speed be used to estimate effects of distributed propulsion?

Can prop exit speed be used to estimate effects of distributed propulsion, if the props are in front of the wing? If distributed propulsion is "just extra air", it is similar to the wings just seeing ...
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168 views

Why are winglets swept back and not front?

A winglet is defined by its airfoil shape, profile, sweep angle and height. In case of the sweep angle, why does it always mean that the winglet is swept back. What is the disadvantage of having a ...
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196 views

Could a shrouded fan blade with long chord length be efficient?

I am wondering if it would work to have a fan with two or three blades which have short-ish span and very long chord length, like half a rotation for each blade. Would a shroud (that is molded on the ...
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1answer
140 views

Will an axial compressor work with an ideal fluid?

Will an axial compressor, like the one described starting on page 275 of this book, work if the flow was assumed to be ideal (i.e. incompressible and inviscid)? Specifically, what mechanism will slow ...
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What effect does wing loading (high and low) have on aircraft performance?

I've read that stalling speed is partly determined by wing loading. Correct me of I'm wrong - "Aircraft with high loading have more weight relative to their wing area hence the stall speed is ...
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Why does the use of reverse thrust on the DC-8 generate a pitch-up moment rather than a pitch-down moment?

Unlike most aircraft, the DC-8 is certified to use reverse thrust in flight (albeit only on its inboard engines). This serves as a very effective airbrake, although it also produces considerable ...
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Since shock waves have non-negligible viscosity, why do the normal shock relations ignore friction/viscosity?

The normal shock relations (seen below) are derived by using steady, 1D, neglect potential, no shaft work, adiabatic and zero viscosity assumption. However, since shock waves are "thin regions of high ...
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Difference between symmetrical and cambered airofoil?

I have seen images of cambered and symmetrical wings but apart from that what are the major differences between them? I have also read that symmetric wings don't produce any lift at 0° AOA whereas ...
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How do planes maintain constant speeds at cruise altitudes?

I'm a noob so pardon my ignorance. So my understanding is that as the plane gets lighter during the flight, its mass reduces therefore reducing the lift needed to maintain the altitude. At those ...
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How do I choose the correct params?

I am very new to airplane design. I am working on this project to design a flying wing glider (no propeller) that would glide in a circular pattern with a fixed radius of 250 m after being released at ...
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61 views

What parameters to focus on when constructing a wing for turning? [closed]

I want to construct a flying wing (glider) with the sole purpose of performing a helical turn (or a circular turn with no propulsion attached) with somewhat of a fixed radius. What should be the main ...
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Is it possible to stall a plane so badly that the nose refuses to go down due to lack of airspeed?

So basically, a stall from a high AoA to the point that the entire plane just falls with the rear end pointing straight down? Because if wind is no longer passing over the wings, then this includes ...
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How does the ground effect affects longitudinal stability?

I recently learned that the ground effect increases the effective AoA of the wing and thus increases lift, how does that translates in to the tail plane and it's stabilizing effects? does it reduce/...
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Does the F-16's neutral stability also extend to the negative-G flight regime?

If an F-16 pilot pushes the stick forward hard enough to send the aircraft into negative-G flight, does the jet tend to accentuate the new flightpath, requiring the pilot to counter that, or not?
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Is the Reynolds number the same for both the airfoil and wing? If not, why/how does it change?

This question might be stupid, but I don't understand this one thing: does the Reynolds number change when you go from the airfoil to the wing? Or is it the same for both?
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Is Turn and slip indicator a good back-up for the attitude indicator?

I was reading my Aircraft general knowledge book, and noticed something peculiar that was written. The book described that the turn and slip indicator works as a back-up in case of a malfunctioning ...
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Why is the circulation around a centrifugal impeller blade tip the opposite to a wing tip?

Why does the circulation around a centrifugal pump blade tip go from low pressure to high pressure as an effect of the slip caused by the non-uniform velocity distribution (the opposite of a wing tip)....
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Why does a turn and slip indicator matter?

I'm studying the principles of flight, and I'm having some unanswered questions in my mind regarding the turn and slip indicator. I'm reading that a turn and slip indicator displays the slip or skid ...
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Where can I find data comparing coefficient of lift (and drag) curves for any airfoil with and without flaps deployed

I'm doing my masters thesis on a FISHBAC wing so I'm hoping to find coefficient of lift and drag curves for any airfoil with and without (any type of) flaps deployed (and preferably leading edge ...
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Do afterburners use excessive amounts of fuel?

The purpose of an afterburner is to provide additional thrust, and it is obvious that more fuel is needed for that. But that is to be expected independent of an afterburner. That more thrust needs ...
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Is an afterburner louder than the same jet engine without it?

I would speculate that an afterburner increases the noise because it is nearer to the exhaust. But it certainly causes so many changes in the exhaust flow that it could be less loud as well. It may ...
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What area to use for the lift/drag forces [closed]

I'm trying to model the orbit of a satellite around the earth at 500km above the surface. I have the nose cone radius and the surface area of the wings so should I be using the cone radius for the ...
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What is the effect of moving a propeller closer to a wing?

Does it improve efficiency? What if the wing is just a plate? Certainly increasing plate thickness will decrease efficiency.
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Flying a twin engine aircraft with 2-axis control

I believe a twin engine aircraft, with 2-axis control (i.e. Rudder and Elevator), under normal circumstances is flyable. But is it safe at all? If one of the engine dies, will the rudder alone be ...
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Are there any lift or lift coefficient equations which factor in the flap deflection angle?

I'm asking this because I tested a NACA 2412 wing with an adjustable flap in a subsonic wind tunnel and I'm getting the lowest Cl values for the highest flap deflection angle.. which to my knowledge ...
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Calculating lift with lifting-line theory in MATLAB

I am attempting to calculate the lift generated by a model wing (~0.8$m^2$ wing area) using Prandtl's lifting-line theory in MATLAB. I am starting with the equation below from Anderson's 2005 book ...