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Questions tagged [transonic]

Use for questions related to the transition between subsonic and supersonic flows, like flight at speeds close to Mach 1 or supercritical wing design.

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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 ...
Alastair Wyllie's user avatar
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1 answer
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Why would there be a drag discrepency when simulating transonic flow over scaled CRM geometry?

I have a discrepancy when simulating a wind tunnel experiment of a 2.7% scaled NASA CRM geometry as used in the wind tunnel. I am trying to replicate exactly the wind tunnel model and flow conditions ...
Sharan S Pant's user avatar
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1 answer
127 views

Why do the shocks on the upper and lower surfaces of a wing stop at the trailing edge? [duplicate]

Why do the shocks on the upper and lower surfaces of a wing stop at the trailing edge? When going Mach 0.82, the shocks on the upper (and lower) surface don't go the whole chord length of the wing. (...
Wyatt's user avatar
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Am I correct with my thoughts of supersonic vs. subsonic flow?

So I'll just list a few things that I thought were correct. If there's anything I'm wrong about, I'd appreciate if someone could explain where I went wrong. In supersonic (vs. subsonic) flow, the lift ...
Wyatt's user avatar
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150 views

How do transonic or supersonic speeds affect lift distribution of the entire wing?

I've written a few questions about this topic, but this part I never asked. How do supersonic or transonic speeds affect lift distribution over the whole wing? How does the root's changing pressure ...
Wyatt's user avatar
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2 votes
1 answer
83 views

If I know both Re number and Mach, how do I incorporate both into my simulation?

I’m trying to simulate an aerofoil based on experimental data with flow in the following conditions: Mach=0.84 Reynolds number (Re) = 3*10^6 I wanted to keep my chord length at 1unit but then what ...
SirTimothy's user avatar
2 votes
2 answers
183 views

Why would a lower trailing edge angle allow for more rear-loading?

In reading a paper on transonic aerodynamics by Jeff Jupp (Chief Wing Designer for the A310), he states, "the trailing edge angle in modern airfoils is reducing significantly, almost to zero in ...
interested22's user avatar
2 votes
1 answer
92 views

Can someone recommend a good book/paper on understanding shockwaves over aerofoil? [closed]

I’ve been trying to understand shockwaves around an aerofoil from some contour plots I saw here and on the internet, but I’m struggling to understand them Can someone please recommend a good book on ...
FlightWatcher's user avatar
3 votes
2 answers
264 views

Why do shockwaves move aft with camber/trailing edge deflection? [closed]

Why does a shockwave move further towards the trailing edge with increasing camber? Also, is the shockwave the thing above the aerofoil or behind it?
MartinB's user avatar
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What are the exit temperatures of bypass flow

Consider a typical high bypass turbofan designed for cruise at approximately mach 0.8, with a separate nozzle for the bypass air. Ideally, the bypass air would be compressed adiabatically by the ...
Ögmundur Eiriksson's user avatar
3 votes
1 answer
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Why does the condensation cone disappears when the airplane starts flying supersonic

In this answer How are condensation cones created by supersonic airplanes? it is said that the condensation cones appear only when the airplane flies at speeds below Mach 1. I am wandering why does it ...
Konrad's user avatar
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4 votes
1 answer
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Why does air density drop when speed nears the Mach 1?

In many questions and answers about high speed aerodynamics here it is said that as speed approaches the speed of sound, there is also a decrease in air density. Can someone explain why?.
Konrad's user avatar
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Why have supercritical airfoils not been used in designing the propeller blades?

In terms of specific fuel consumption, propellers are more economic than jet engines at low speeds (<0.5 Mach) but at high speeds, the propeller blade tip reaches locally to supersonic speeds which ...
Dhirendu Somani's user avatar
1 vote
0 answers
71 views

How have aerodynamicists improved transonic wing performance over time?

The following two graphs depict improvements in transonic wing technology that have occurred over the past 20-25 years. Both are sourced from Boeing Commercial Aircraft. In essence, both note that ...
interested22's user avatar
0 votes
1 answer
366 views

Are there planes designed for going supersonic in a dive only, not in leveled flight?

Are there any sub-/transsonic planes that are able to go supersonic in a dive without damage nor losing control but can't go above Mach 1 in horizontal flight? Some planes can go into leveled ...
Giovanni's user avatar
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3 votes
1 answer
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What does account for a high coffin corner of a plane?

The Coffin corner is the altitude at which a plane's stall speed is close to Mach 1, the speed of sound (but still below, at the critical Mach number). What accounts for a coffin corner at higher ...
Giovanni's user avatar
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2 votes
1 answer
679 views

Why would control-surface balance horns cause problems at transonic speeds?

On many aircraft, control surfaces such as elevators, ailerons, rudders, etc., have "horns" which extend forwards of the surface's hingeline, wrapping around the tip of the wing or ...
Vikki's user avatar
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6 votes
1 answer
887 views

How does the drag coefficient behave at transonic and supersonic speeds for swept wing aircraft?

I was reading about wave drag and Concorde recently and found some contradictory information relating to drag. For example Wikipedia says: Afterburner was added to Concorde for take-off to cope with ...
mikol's user avatar
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14 votes
2 answers
4k views

Why are the grid fins on Starship pointy and sharp?

The grid fins on Starship are serrated, why? Does it help in transonic maneuvers? Source: Starbase Factory Tour with Elon Musk [Part 1], YouTube, at 30:28
Pioneer's user avatar
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16 votes
8 answers
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Could an airliner exceed Mach 1 in a zero-G power dive and safely recover?

(I looked for duplicates. I really did.) Being as it is that "safety" and this are mutually exclusive: I am stupid. I take a cruising A320, apply TOGA power, and push zero Gs until I exceed ...
Abdullah is not an Amalekite's user avatar
41 votes
3 answers
10k views

Is it dangerous for a supersonic aircraft to fly at exactly Mach 1?

If a plane that is designed for supersonic flight, say the Concorde, kept flying at exactly the speed of sound, would there be any danger in that? If so, what could get dangerous at constant Mach 1 ...
Giovanni's user avatar
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-1 votes
1 answer
140 views

What are the difficulties in building transonic airliners?

If the sonic boom is an issue, why don't we build airliners that are capable of flying just below Mach 1? Big airliners fly at Mach 0.85 at most, and the record for current sub-/transonic civilian ...
Giovanni's user avatar
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2 votes
2 answers
201 views

Why do semitailless swept-winged aircraft, but not delta-winged aircraft, suffer from (primarily) pitch oscillations at high mach?

Semitailless1 swept-wing aircraft without active stability enhancement2 generally3 have extremely poor handling characteristics, most notably a tendency towards violent pitch oscillations at high ...
Vikki's user avatar
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12 votes
2 answers
2k views

Why does directional stability decrease at supersonic speeds?

As an aircraft accelerates through the transonic region from full subsonic to to full supersonic flow its directional or yaw stability decreases. What causes this reduction?
Guy Inchbald's user avatar
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5 votes
2 answers
1k views

Why do shockwaves progressively move aft as speed increses?

As an airfoil moves from subsonic to supersonic, the shocks that develop over the surface move progressively toward the trailing edge. What is the physical explanation for this behavior? As a side ...
Nick Hill's user avatar
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3 votes
2 answers
2k views

Why do swept wings decrease the drag increase that occurs in transonic flows?

Swept wings are used in aircraft that fly in the transonic regime because they 1) delay the critical Mach number 2) reduce the drag increase that occurs (smaller drag divergence). I am trying to ...
Nick Hill's user avatar
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0 votes
2 answers
503 views

How to reduce the noise of the supersonic passage(bang)?

as you know the transonic phase is often associate with the bang. The principal cons of the transonic phase is the noise,it's why there is not supersonic passenger aircraft( cause the end of the ...
L'aviateur's user avatar
4 votes
1 answer
284 views

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 ...
Nick Hill's user avatar
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1 answer
287 views

Is the highly optimized high subsonic cruise airfoil less safe for higher AOA flight? [duplicate]

An examination of the 737 airliner wing profile and that of a blue whale leads to the question of whether the high Reynolds number subsonic cruising airfoil and the low speed, high AOA airfoil are ...
Robert DiGiovanni's user avatar
6 votes
1 answer
1k views

Why do 20-series Learjets have such an extreme susceptibility to mach tuck?

Mach tuck is a change (usually nosedown) in an aircraft’s pitching tendency during transonic flight relative to its pitching tendency in below-transonic flight, caused by the appearance of areas of ...
Vikki's user avatar
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2 votes
2 answers
2k views

Why does transonic drag happen?

I have heard of transonic speed and it is between supersonic and not supersonic. What is it and why does it happen to aircraft and how does it produce a lot of drag. How do you prevent it from ...
Zac Callaghan's user avatar
5 votes
1 answer
581 views

How does a weak shock-wave boundary-layer interaction create wave drag (other than through direct shock losses)?

I'm trying to understand the physical cause of wave drag, beyond the simple statement "the presence of shockwaves increases the drag". As far as I understand, in the case of a weak BLSWI (so without ...
Daniel's user avatar
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8 votes
2 answers
941 views

Transonic buffet - reason for a rapid movements of the shockwave along the wing chord line?

I know that transonic aerodynamic buffet is caused by the separated turbulent boundary layer striking the airframe (horizontal stabilizer, wings, fuselage) with considerable force causing a high ...
Darjan's user avatar
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10 votes
1 answer
1k views

Why do some Mach trimmers move the elevator?

A pop-up rod on a the FO's control column on a DC-9 that shows the Mach trim position. (YouTube) Regarding the title, I'm not sure if it's just some or all jetliners (I tried to research it). On the ...
user avatar
3 votes
1 answer
751 views

Are there any airliner crashes that can be definitively attributed to Mach tuck?

Mach tuck (the tendency of aircraft to develop an increasingly nose-down pitching moment at speeds above its critical mach number) caused a number of crashes of high-speed fighter aircraft before the ...
Vikki's user avatar
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2 votes
0 answers
612 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 ...
Francis L.'s user avatar
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1 vote
1 answer
178 views

What is the ideal volume distribution for minimization of transonic drag?

I am aware what the area rule states - my question is what is defined as "as smooth as possible area distribution" - Is there a formula for the curve?
Krzysztof Broda's user avatar
3 votes
2 answers
4k views

What are the effects of shockwaves on normal and supersonic aircraft?

What are the effects on the speed of the plane, does it effects the body of the plane, and do shockwaves cause major damage to the plane. I know that flying at Mach 1 is really risky, but what's the ...
djk's user avatar
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5 votes
1 answer
2k views

What's the relationship between drag divergence Mach number and maximum operating limit Mach number?

The drag divergence Mach number, also known as the force divergence Mach number, is the Mach number where drag waves start to form. The drag divergence Mach number is typically between 5 to 10 ...
lemonincider's user avatar
  • 7,565
14 votes
1 answer
601 views

Can a transonic airfoil have two shock waves?

I am currently running CFD cases on a transonic airfoil at Mach 0.75 and performing an angle-of-attack sweep to evaluate its performance. When I reached the angle of attack of 4.5 degrees (which I ...
GSammons's user avatar
  • 307
8 votes
3 answers
2k views

Is it possible to hear a sonic boom when the aircraft is exactly at Mach one?

Will an observer on the ground hear a sonic boom if a plane passes overhead at exactly the speed of sound? That is, the plane does not cross the sound barrier. The plane just hits Mach one - and ...
vikram dhar's user avatar
2 votes
2 answers
2k views

Does the sound barrier apply to a silent aircraft? [duplicate]

For my summer duty, I was looking at the sound barrier effects with a glimmer of hope to understand them: "A supersonic aircraft is one that can travel faster that the speed of sound. As the plane ...
mins's user avatar
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6 votes
1 answer
446 views

What would the density profile of this shock wave look like, roughly?

The YouTube video titled Shock Wave Formation in Transonic Flight shows a hand-held video of a visible shock wave extending from the top of a jet engine near the front. The shock wave is visible by ...
uhoh's user avatar
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2 votes
1 answer
1k views

How does airfoil thickness affect the Mach number at which it experiences transonic flow?

Roskam (book: Airplane Aerodynamics and Performance, Subparagraph: 2.5.2 HIGH-SPEED AIRSPEED INDICATORS (COMPRESSIBLE FLOW)) affirms: [...] Airplane with no sweep and thick airfoils become ...
d.pensopositivo's user avatar