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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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Can be the divergence Mach be greater than 1?

I am wondering if this is possible. I know that by decreasing t/c and increasing the sweep angle it is possible to increase the divergence Mach. Where is the limit? I am calculating the Mach for a ...
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1answer
135 views

Is there a difference in stability between a tail downforce (cg ahead of ac) and a tail upforce (cg behind)?

So from what I understand, having a - 1.cg ahead of the neutral point(ac) with a tail downforce and 2.cg behind ac with a tail upforce are both stable configurations.(Please correct me if I'm ...
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850 views

What is the 'end plate' effect?

When talking about T-tail configuration, I don't understand the statement that, "The vertical tail can be shorter due to the end plate effect of the horizontal tail." What exactly is the endplate ...
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411 views

Do airliner spoilers really “spoil” lift?

The two illustrations below show the typical spoiler location and the lift distribution of a wing. For comparison a third picture shows the location of spoilers on a glider. It appears the airliner ...
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1answer
585 views

What are the consequences of attaching an unused extra engine under Boeing 747 wing?

It turns out Boeing 747 can carry an extra engine under its left wing in case there's need to transport an engine somewhere far away. The engine is attached between the body and the left inner engine ...
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1answer
135 views

Is using flaps the same as increasing the AOA? [duplicate]

The purpose of trailing edge flaps is to give the aircraft more lift at lower speeds. But do simple flaps beneficent more than increasing the angle of attack? The image looks like part of the wing ...
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2answers
220 views

What aerodynamic phenomenae can decrease the pressure gradient in Boundary Layer Ingestion?

I'm exploring a question concerning whether or not boundary layer airflow presents physical limitations that are too great for current technologies to overcome (I'm holding the position that it is in ...
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1answer
90 views

Do the elevators generate vortices? [duplicate]

I want to know whether the elevators generate vortices like the wings do? If yes, then where do the vortices form?
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2answers
179 views

How does an aircraft's weight affect the V-n diagram?

I have a reasonable understanding of what a V-n diagram shows and what the envelope and the boundaries mean. However, the question I have is how does the weight of the aircraft specifically affect the ...
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105 views

How can I find or calculate typical flutter velocities for different wings?

I need to validate a code I wrote for calculation of dynamic aeroelastic response of a wing for my aeronautical engineering Master thesis. I'd like to ask if anyone may provide me a list with typical ...
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3answers
367 views

Can airplane performance be increased by cruising “on step”?

Old timers swear aircraft performance can be increased by getting an aircraft "on step" similar to how boats are operated. They claimed a couple extra miles per hour (airspeed was in MPH then) were ...
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4answers
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Is this paragraph about the dihedral effect in the FAA's Glider Flying Handbook correct?

I've been reading the FAA's Glider Flying Handbook, 2013 (FAA-H-8083-13A). In chapter 3 ("Aerodynamics of Flight"), the book is discussing stability. On page 3-12, it states: Dihedral is the upward ...
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1answer
356 views

How does a Hawk jet avoid pitching down when its air brake is applied

Some aircraft have air brakes in an aerodynamically neutral position with respect to rotational forces on the airframe (e.g. F-15)... source ... more often, others have brakes that are ...
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1answer
359 views

Why does aircraft stability increase when it transitions from subsonic to supersonic flight?

I am puzzled why would the aircraft be more stable at high speed flight at high altitudes. Given that the Centre or Pressure moves gradually towards the 50% MAC region, once past Mcrit. Has this got ...
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Why do most biplanes have their top wing slightly forward of the lower wing?

In most of the biplanes, the top wing is located a little forward of the lower wing. What is the use of this? Also, how does this affect stability of the aircraft.
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How do I find experimental Cp, Cd and Cl values for a NACA0012 airfoil? [duplicate]

How can I get experimental Cp, Cd and Cl values for a NACA0012 airfoil where Chord length=240mm and Re=4.6e5? I'm looking for both 2D and 3D airfoil/wing (infinite span). I understand that plenty of ...
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293 views

In a jet, are Vy and Vx achieved at a constant AOA at all altitudes?

It is known that in terms of IAS, Vx (best climb angle speed) rises with altitude, and Vy (best climb rate speed) decreases with altitude, until they converge at the plane's absolute ceiling. http://...
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1answer
120 views

Why changes the lift during turning with sidewinds? Why is there relative wind in the wind-frame?

I started doing some simulations with XPlane and could observe a very interesting effect when doing turns in the presence of constant wind: All simulations are done with the XPlane Cessna 172 (?) ...
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1answer
187 views

Why is the Aerodynamic Centre not affected by changes in Angle of Attack? [duplicate]

I understand that the Aerodynamic Centre (AC) is the point in the aircraft where the pitching moment never changes with a change in Angle of Attack (AoA). My understanding of the Centre of Pressure (...
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63 views

How does a mixer reduce noise in a turbofan engine?

I want to know how does a mixer reduce noise in a turbofan engine? How does its shape influence the flow and the acoustics of the output air generally?
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2answers
1k views

Why does the stagnation point on airfoil move with the angle of attack?

What is the physical explanation for the reason the stagnation point is where it is? And, why does it move further down the lower side of the airfoil with an increase in angle of attack?
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1answer
138 views

Are there multiple reasons for the decrease in pressure over a wing?

I'm aware that the decrease in pressure over the wing is due to the curvature of the airfoil which causes a pressure loss due to the spreading of the air as it is redirected. But is it also due to ...
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1answer
167 views

How does the position of the center of pressure change with the use of different high lift devices?

How is the position of the center of pressure affected by different high lift device deployments? My guesses are: When I use a high lift device that just increases the chord length, it moves ...
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1answer
397 views

“Fundamental of Aerodynamics” 5th editon, example about oblique shock. Is the author's solution wrong?

I am reading "Fundamentals of Aerodynamics" 5th edition, J.D.Anderson. If you have the book, go to chapter 9: Oblique shock and expansion waves. Please look at example 9.2, page 618: Consider a ...
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2answers
252 views

Why does a 3D wing's CL keep increasing even after 50° AOA in XFLR5?

Can you please tell why my 3D wing in XFLR5 keeps increasing it's lift even after 50 degree AOA, while it's 2D profile stalls after about 10 degrees ? More details on simulation setup: Airspeed is ...
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2answers
216 views

How can larger wingspan decrease the strength of wingtip vortices?

In the last paragraph from the link below, it states that Vortex Strength is inversely proportional to Wingspan. Why is this? http://avstop.com/ac/flighttrainghandbook/wingtipvortices.html EDIT: ...
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94 views

How can I calculate the lift force on an aircraft pulling out of a dive?

Any ideas on how this question is answered? Consider an aircraft dived [sic] along a path inclined to horizontal, perhaps even a vertical path. The manoeuvre whereby the aircraft recovers from ...
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2answers
538 views

How can I calculate CLmax for a wing with multiple airfoils?

How should I do the math to find the CLmax of a wing that has more than one airfoil, each with a different CLmax? I am trying to make a model with a portion of the wing tip with a airfoil that has a ...
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2answers
114 views

Is the lift produced by a wing with a 10° flap equal to the lift created by a wing with 10° AOA but with no flap?

After reading this article I would like to know if the lift produced by a wing with a 10° flap is equal to the lift created by a wing with 10° AOA but with no flap?
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72 views

What does “lower flatness” mean in airfoil terminology?

What does lower flatness mean in these parameters of a Glenn Martin airfoil?
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338 views

What aircraft has the highest critical Mach number?

What aircraft has the highest critical Mach number? The highest I heard of was BAC/English Electric Lightning at Mach 0.95. Are there planes with higher Mcrit. and is it plausible to go higher than ...
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3answers
530 views

Aerodynamics of double winglets

I've read here on Aviation SE that the aerodynamics of winglets on an aircraft are easily described as "extending the airfoil". Thus, as I understand it, a winglet is like stretching the airfoil a ...
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475 views

Can an aileron stall in-flight?

Horizontal stabilizers stall, so I was wondering, is it possible for an aileron to stall? If yes, at what angle of attack?
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2answers
99 views

Does Karman line depend on the wing area, and if not, why?

The Karman line is the altitude at that the airspeed required to generate the sufficient lift to support itself exceeds the orbital speed. Looks like the Karman line is defined as some fixed value, ...
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1answer
90 views

Where can I find this transonic prop airfoil?

I am interested in identifying this prop airfoil due to its uncommon high .92% efficiency (the best metal props are closer to 83-87%). I have done an exhaustive search for it. It is labeled "NACA RML ...
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1answer
339 views

When are winglets most effective?

If winglets reduce induced drag, induced drag is greatest at slow speeds. When are winglets most effictive?
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1answer
170 views

How come diverterless supersonic inlets haven't been discovered much earlier?

DSI's seem like such an absolutely elegant solution to a problem that has, so far, been solved in a truly overly complicated way. So, if I'm not missing out on some important small speck of knowledge ...
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5answers
422 views

Is wing sweep needed on supersonic aircraft?

Area rule states that bodies with the same crossectional area distribution have the same drag. Does that mean I could use a straight wing on mach 1.2 aircraft with performance as high as sweep winged ...
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1answer
110 views

Twist optimization for a low speed aircraft

I'm currently designing an aircraft with the following specifications- s=1.8m^2, AR=7-8, trapezoidal planform with a taper ratio of about 0.45, a load of 25KGs and a cruising speed of 13-15m/s. I'm ...
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2answers
455 views

Why is the critical AoA of most flaps 40° when most airfoils stall at 15°?

A plain flap deflected 40 degrees is largely stalled (...) Flaps stall at 40° according to an answer on Quora, why is this so when typical airfoils stall at 15°?
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2answers
406 views

Why do compressors constrict flow if this decreases pressure?

An axial compressor (and a ramjet intake, for that matter) is commonly depicted as decreasing the volume of air travelling through as we move closer to the combustion chamber. In axial compressors, ...
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3answers
283 views

How does the wraparound wing design reduce drag?

How does the wraparound wing in this AOPA article reduce drag? One would think all that extra leading edge and surface area would make it worse. One more link also. The Parsifal Project has ...
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1answer
394 views

Could Mach 1.4 be a better design point for SST?

There's been a number of recent proposals for design work on low-supersonic bizjets that would cruise at Mach 1.1-1.6, the common theme being avoiding a sonic boom. I'm wondering if this range of ...
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If elliptical lift distribution is considered in every case, does the induced velocity change based on the shape of the wing?

Shapes like rectangular, curved, trapezoidal etc. Here I mean rectangular or curved when viewed from the top. The sectional airfoil shape is the same in each case.
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3answers
595 views

How does the nozzle diameter affect the thrust of a ducted propeller?

I currently do some experiments with ducted propellers in which I try to figure out which effect a nozzle has on the thrust produced. My theory goes like this: If I reduce the exit diameter of the ...
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1answer
285 views

Why are some Tomahawk missiles' nose duck-nose shaped?

Why there is a duck-like shape in this Tomahawk missile's nose? I see this shape in most Tomahawk images; however, not every Tomahawk's nose is shaped like this. If it is an aerodynamic feature, ...
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2answers
500 views

Is there a downwash equation?

I need to find an equation for the following problem: Suppose a full-size glider passes 10 feet over my head at high speed. No doubt I will feel the downward air pressure (downwash) caused by the ...
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117 views

Hovering propeller: how to calculate Chord length and Advance ratio? [duplicate]

friends ! I would like to design a propeller for my drone with specific weight and power requirements. The drone will either hover or fly slowly. It is kind of clear how to select an angle of attack ...
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0answers
107 views

Why double delta wing is used over delta wing? [duplicate]

I was thinking about delta wing then I saw the picture of double delta wing and thinking about its significance over delta wing.
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5answers
477 views

Why wing ribs have diagonal struts

Why do ribs have diagonal struts,why not vertical as seen in airfoils of Citabria airplane?