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 to create a simple forces diagram using only lift and drag forces?

I would like to create a simple forces diagram (like a sketch). The lift produced by the wing depends upon to the distance from the the longitudinal axis, but, in order to make it easier, I’m taking ...
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What does induced flow exactly means on helicopters flight? How is it different from downward deflection of air?

I believe all airfoils deflect air downwards at an angle at a velocity V. What is the difference between the downward-vertical component of the deflected wind and the induced velocity in Helicopter ...
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How is the wingspan of a wing measured if it has a dihedral? [duplicate]

I am having some confusion regarding how the wingspan is measured, I just wanted some clarity because this was bugging me while I was reading about aircraft wings. According to NASA's "Wing Geometry ...
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How can we physically define reynold number variation in terms of characteristic length? [closed]

How can you define it physically that greater the characteristic length in $Re=\frac{\rho v L_c}{\mu}$ greater the Reynolds number. Like on wing surface $Re$ is higher than the horizontal tail surface ...
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What causes lift in aerofoil: Bernouli's principle or Newton's third law? [duplicate]

Reading materials online, I observe some explanation based on Bernoulli's principle, quoting the difference of air pressure above/below and difference of speed of airflow. While some say's Bernoulli's ...
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Helicopter flight: Does the rotor disc plane and hub plane rotate along axis perpendicular to rotational axis?

In many pieces of literature, diagrams as below are shown to explain the directional flight of Helicopter. I have the understanding that the cyclic input will only change the pitch angle of the blades ...
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3answers
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Do adding high thrust in plane prevents it from stalling?

I am convinced that fighter jets(every flying object) do stall .So from quora, Why don't fighter jets stall? But most of the fighters have thrust:Weight ratio > 1 which means that they are not ...
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Would using a full span spoiler and a separate flap be a better design than a flaperon for a STOL ultralight?

Would using a full span spoiler and a separate flap be a better design than a flaperon for a STOL ultralight? I understand most airplanes use 50% flaps and 50% ailerons. The problem with this, is ...
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How does vertical stabilisation work?

I know that similar questions are available all over the internet, including this website. However, none of the answers make full sense to me. I'm looking for simple answer (explain-like-I-am-5 type ...
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Why are there some fixed surfaces on the tail cone of some planes? [closed]

I am not a plane specialist. Why are there some kind of fixed surfaces at the rear close to the tail cone pointing downward? Like on the pilatus pc12
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Why do some T-tail aircraft have a protrusion on the top front of the tail? [duplicate]

Aircraft like the Tu-154 and VC-10 have a "point" on the T-tail, while others like the 727 do not. Is this structure a shock body, or otherwise related to the tail's aerodynamics? And why is it only ...
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Formula needs another formula's answer to solve, which in turn needs the first formula's answer to solve [closed]

Why do some equations require each other to calculate? For example, the formula of drag coefficient requires the force of drag to calculate, while the drag force equation requires the coefficient of ...
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Can an automatic gearbox improve engine transmission for an ultralight? [duplicate]

I am working on my dream to build and fly an ultralight aircraft so I wouldn't like to know the following: Does adding a motorcycle automatic gear box to an engine improve on the strength for an ...
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Why are there so few carrier capable delta wing aircraft?

When looking through various carrier aircraft, I noticed that there seemed to be very few with delta wings. While initially chalking this up to higher stall speeds necessitating higher approach speeds ...
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Why don't ailerons affect pitch?

Why don't ailerons affect pitch, or do they? I'm told spoilers can affect pitch if not placed in the right spot. On a classic standard wing configuration, why don't ailerons affect pitch as they are ...
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When a paraglider pilot applies brake on one side and maintains the brake pressure, why does the roll rate eventually come to zero?

I recently started to study paragliding and I am confused about the rolling movement created when a brake is maintained. I was reading this answer How do paraglider controls work? and I am not clear ...
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What are aerodynamical reasons behind slight dihedral or no dihedral at all? [duplicate]

Regarding general aviation single engine high wing aircrafts in particular, what are the reasons for some of them to have no dihedral at all on their wing, or slight positive dihedral angle for other? ...
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Questions in choosing a Cm curve for an ultralight?

Questions in choosing a Cm curve for an ultralight? What slope should it be for a docile ultralight, 12 lbs per sq ft wing loading? About 20 deg downward to the right ( subject to final stability ...
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Are standardized tail volumes used for swept wing GA aircraft like in straight wing designs? If so, what are they?

Are standardized tail volumes used for swept wing GA aircraft like in straight wing designs? If so, what are they? I understand that after roughly 100 years of aircraft design, there are rules of ...
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How to find the static stall angle of attack for a given airfoil at given Re?

For vertical axis wind turbines applications I'm wondering how one would find the static stall angle of an airfoil at a given Reynold number? Is it just the critical angle of attach (AoA) where ...
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Is it possible to have an angle of incidence for a vertical stabilizer?

horizontal surfaces in airplane have small angle of incidence in general, Is it possible to have an angle of incidence for a vertical stabilizer? Please help me to find it. Thanks!!
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How does washout increase static pitch stability in subsonic swept wings?

How does washout increase static pitch stability in subsonic swept wings, more specifically in slow moving aircraft (eg. ultralights), 15mph to 60mph? I understand washout is used to delay full ...
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Why does disk loading mean anything when rotors/propellers are not disks?

"The helicopter rotor is modeled as an infinitely thin disc with an infinite number of blades that induce a constant pressure jump over the disk area and along the axis of rotation." This is ...
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Are larger airplanes more likely to stall?

Stalls happen when the boundary layer on top of a wing slows so much that it essentially becomes part of the airfoil. My question is, as the wings on larger aircraft present a longer flow path for ...
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What are typical values of the lift-to-drag ratio for normal small aircraft?

Hi I am trying to do a rough estimation of forces acting on an aircraft wing and would like to know what kind of lift to drag ratio is normal. The exact profile hasn't been chosen yet, but the ...
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Helicopter Flight: What is the reason for decrease in Induced drag with increase in speed?

As per the figure the induced drag will decrease only if the AoA of the blade is decreased — But in the forward flight, cyclic input increases and decreases the AoA throughout the blade rotation cycle....
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In which direction does air flow over a wing as observed from ground?

A wing flies to the left in the air (no wind). Particles A and B moves to the right in relation to wing. In which direction do particles A and B moves in relation to the ground? What is velocity of ...
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VLM at High Speeds and High Angle of Attack

I want to analyze a plane of the size and speed of a commercial jetliner. I have made the model of it on OpenVSP. I am using VSPAero's Vortice Lattice Method for the same. I want to analyze the plane ...
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Is drag the only aerodynamic force that acts upon an asymmetric body (a glider in particular) travelling through the air?

It is known that for a symmetric body, like a sphere falling through the air, the only aerodynamic force that acts upon it is the drag that points always in the opposite direction relative to its ...
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Blunt noses subsonic drag - why a complete ellipse?

At subsonic speeds, blunt noses - both fuselage and airfoil - are good for two reasons: the need to maintain attached flow at varying angles of attack. it has less surface area for the volume, ...
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Is it possible to have the laminar flow above $Re=10^7$?

For pipe flow I came across the information that the onset of turbulent flow occurs at approximately $Re=10^3$ to $Re=10^4$, while for boundary layers on the airfoil the onset occurs in between $Re=10^...
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Is there any go to formula in the designing of a winglet? [duplicate]

we have to design a commercial airplane as a part of a college assignment and i was wondering if there are any rule of thumb /formulas involved in the designing of winglets? Or does one have to assume ...
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Why is it harder to maintain laminar flow on larger aircraft?

I am told that on larger aircraft, suction will be needed to maintain laminar flow because of the larger leading edge radius. Why so? Is it because the air has to travel over a longer distance on the ...
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Is the ratio of HP to weight constant for identical air frames of different sizes? (See Scenario)

In my head it seems logical that there would be a proportion between engine HP and empty weight. For example, the Wright Flyer weighed around 600 LBS empty and had a 12 HP engine. If I were to make an ...
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How pressure fields change around wing?

In the 3D case,downward turning is immediately above and below the wing is stronger than in 2D case,for the same lift.This is because more rapid dying off the pressure above and below the airfoil ...
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In helicopter's forward motion, how is the forward pitching moment taken care off?

When the rotor disk is in the position shown by the dashed lines, the net Lift is at an angle. It should produce a forward pitching moment about CG (Center of gravity). That can cause the helicopter ...
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Why is a centrifugal compressor in aircraft engine less susceptible to stall and surge?

I have came across a similar question here. Although the answer doesn't explain much about why and is somewhat vague. I have read that centrifugal compressor can achieve a higher pressure rise per ...
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Why do supersonic and hypersonic planes have a pointed nose whereas commercial planes have a round nose [duplicate]

We see supersonic and hypersonic planes having a pointed nose whereas commercial planes have a round nose.is there aerodynamic reason for these different design?
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Why is Active Flow Controlnot used in Fan And Compressor of aero engines?

Why active flow control is not used in the compressor and fan of aero engines even though they provide several advantages in terms of performance? what are the challenges of using active flow control ...
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What methods are used for calculating maximum takeoff windspeed of a helicopter?

I would like to calculate the maximum windspeed in which a helicopter may safely take off and safely land, assuming a theoretical wind environment with constant wind direction and no gusts. I ...
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Is alpha induced angle real on 3D wing or just math concept?

Does alpha induced angle/"effective airflow" really exist in real life on 3D wing or this is just mathematical concept for calculate induced drag? (same as lifting line theory-circulation theory is ...
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Are we on the “wrong boat” with eliptical spanload all these years?

In this video AL Bowers (former NASA chief scientis) talk how bell spanload solution can reduce OVERALL DRAG by 60%(11% reduction in total aircraft drag due to spanload, elimination of the tail ...
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Can free flying twin drag rudders be mounted on a stabilator, aerodynamically speaking?

Can free flying twin drag rudders be mounted on a stabilator on an ultralight, aerodynamically speaking, or would it be disadvantageous? I understand free flying rudders need up to 40% less area than ...
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L/D -Bell vs Eliptical spanload?

look at this video from 18:00-21:00 ,Al Bowers talk about benefits of bell spanload compare to classic eliptical..Can someone explain what does it mean in practice examples when design aircrafts: 1)...
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Do motor glider pilots ever “cheat” and use their motors to thermal?

Do motor glider pilots ever "cheat" and use their motors to thermal? I understand there are 2 types of motor gliders: Self launching: with about 80 hp very similar to an ultralight except a lot more ...
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How much is alpha induced angle?

I know that alpha induced rise with increasing AoA but how much is alpha induced in reality ,are we talking about 1-2 degrees or more?
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Design lift coefficient of an airfoil

I have the design lift coefficient of the plane during the cruise condition. Now, I want to calculate the lift coefficient required by the airfoil which makes up the wing, taking into account the ...
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Will 3D wing has smaller drag than 2D at same AoA and airflow speed?

We meassure lift and drag for 2D and 3D wing case,we use same airfoil at same AoA and same airflow speed for both case. Wind tunnel can change test section walls width. 2D wing test: So first we put ...
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Is an increase in induced drag always caused by an increase in the angle of attack?

In this video at 2:57 they increase the AoA to maintain lift, which normally also increases the drag. Now, imagine that we don't increase the AoA: the drag will not increase but we will not have ...
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Can such an aircraft take off vertically?

The compressor ejects compressed air from the gap at high speed. The red arrow represents the path of compressed air. It is lift that adjusts the speed of the compressed air to adjust the aircraft.

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