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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What is the relationship between AoA and shock wave position in the transonic regime?

I am sure this is a simple relationship whereby as the AoA increase the shock wave moves forward along the upper surface of the aerofoil however I am struggling to find any studies to validate this, ...
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40 views

Is the y+ value still meaningful for aerofoil in transonic flow? [closed]

I am trying to assess the validity of the results of an aerofoil in the transonic regime using CFD methods. I am wondering however, due to the presence of shock waves does this mean that the y+ ...
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214 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 ...
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1answer
202 views

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 ...
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1answer
223 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 ...
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1answer
158 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 ...
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2answers
3k 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
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8answers
6k views

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 ...
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3answers
8k 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 ...
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1answer
111 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 ...
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46 views

Can boundary layer blowing increase transonic efficiency?

One of the problems faced by transonic aircraft is flow separation by recompression shock. Can the pressure drag that arises due to this flow separation be reduced by re-emerging the boundary layer ...
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2answers
154 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 ...
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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?
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312 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 ...
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2answers
545 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 ...
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2answers
324 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 ...
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1answer
204 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 ...
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1answer
202 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 ...
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1answer
833 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 ...
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1answer
772 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 ...
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1answer
341 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 ...
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687 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 ...
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1answer
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 ...
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1answer
439 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 ...
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0answers
513 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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1answer
121 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?
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2answers
3k 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 ...
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1answer
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 ...
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1answer
467 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 ...
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2answers
1k 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 ...
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2answers
1k 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 ...
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1answer
317 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 ...
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1answer
902 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 ...