Questions tagged [shock-waves]

A shock wave is a type of propagating disturbance. When a wave moves faster than the speed of sound in a liquid, gas or plasma (a "fluid", in physics terminology) it is a shock wave. Like an ordinary wave, a shock wave carries energy, and can propagate through a medium. It is characterized by an abrupt, nearly discontinuous change in pressure, temperature and density of the medium. In supersonic flows, expansion is achieved through an expansion fan.

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Why does drag coefficient decrease with Mach number in the supersonic regime?

I'm trying to understand why the drag coefficient decreases in the supersonic regime with Mach number. While it is easy show this using supersonic, potential flow theory, I'm looking for a more ...
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Why doesn't a wing in supersonic flow produce a shock that results in flow parallel to the leading edge?

When we look at a wedge in supersonic flow, a shock emanates from the leading edge such that the flow after the shock is turned and is parallel to the airfoil surface. The shock angle is based on the ...
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How does wing shape impact shock structure?

I am trying to understand what the 3D shock structure would be for a wing in supersonic flow. Suppose we have a wing which is made of double-wedge airfoil cross-sections. If we view the shock ...
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How to avoid shock (particularly Oblique shock) inside Cd nozzle?

Using the Area ratio (A/A*) and for the desired exit Mach number I have designed a cd nozzle. The Inlet total pressure (Po) and the total temperature (To) is calculated using Isentropic relations for ...
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How to identify shock waves and expansion waves on a representation of the mach number?

This image is a representation of the Mach number for $M_{\infty}=2.0$ I am very new to CFD and high speed aerodynamics. I'm trying to analyse this image, specifically to understand why the velocity ...
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Why does the temperature rise in the boundary layer after a shock wave?

Is it because the BL thickens after the shock so the drag increases, causing a increased friction? Here M=0.82 far from the airfoil, the picture represents the static temperature in Kelvins around the ...
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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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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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Shock wave on airfoil

I was wondering the other day, during the trans sonic regime, when the velocity over the airfoil becomes supersonic,why does the shock wave standing on the airfoil moves downstream when the free ...
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How do a narrow airframe and canards keep supersonic shock waves from coalescing?

In a follow up to my previous question: How does the X-59 acheive quiet supersonic flight? Canards and a long narrow airframe were cited as design choices to prevent shock waves from coalescing. How ...
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How does the X-59 acheive quiet supersonic flight?

By what mechanism or combination of mechanisms does the X-59 reduce the noise produced by a sonic boom? What are the design choices that lead to quiet supersonic flight? I really want to understand ...
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How is the camera positioned for these plane-to-plane Schlieren images of shock waves?

These two popular press articles discuss the use of schlieren photography to image shock waves of jets during flight using a special schlieren camera on a third plane. Gizmodo: NASA Captures First-...
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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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Is high speed buffet possible at supersonic speed?

Since high speed buffet is caused by boundary layer separation due to shock wave and at supersonic flight there is no shock wave directly onto the airfoil (it is attached to the trailing edge), is ...
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Why does strong shock wave-boundary-layer interaction produce a bubble reattachment?

The picture represents a lambda type shock wave, separating the boundary layer at its foot. Separation causes a recirculation bubble to appear. I understand why separation has happened, but what is ...
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Do ramjets use variable geometry supersonic inlets?

Ramjets are very often portrayed as super simple, I've read on few occasions that the only moving parts in a ramjet are the fuel pumps. However, turbojets operating at similiar speeds (mach 2 - mach 3)...
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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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How is it possible for supersonic aircraft to push air out of the way?

If the force (pressure) can be transferred/propagated only at the speed of sound, how are supersonic aircraft able to move air out of their way/do work on the air? It seems that they must transfer the ...
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What is primary cause of shock induced separation (shock stall)?

In the video link above describing Prandtl Meyer Waves, lecturer stated (at 22:40) a very important fact on which he based his first half of the lecture. "Mach wave (mach lines) deflect the flow ...
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How can one approximately guesstimate wave drag?

Wave drag is an especially high drag that affects supersonic vehicles above mach 1, but I've found it hard to find source materials to estimate wave drag. I'm looking at the transonic region till Mach ...
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“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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How does the V22 Osprey manage such high rotor speeds without shock waves?

I read somewhere that the engineers presented an ingenious solution to the rotor tip shockwave problem, except the article didn't actually explicitly mention it. So, does anybody actually know if ...
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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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What is the difference between a shock wave and an expansion wave?

Studying high speed aerodynamics I have found a question asking for what happens to static temperature for an airflow passing through an expansion wave. The correct answer states that it decreases- ...
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What happens to the pressure and density of air passing through shock waves?

I understand that the pressure and density of air increase as the air gets closer to shock waves and the pressure and density of air that has escaped the shock waves increase as well. Then, what ...
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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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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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Can a supersonic plane use a subsonic wing if the nosecone shock produces subsonic airflow around the wing?

A supersonic plane will produce shock waves off the nose cone, as seen below: These oblique shocks reduce the speed of the air that the wing experiences. If the plane is at a low enough Mach number, ...
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Why is the flow ahead of a shock wave chaotic?

Here is the image of a shock wave on a cone in a small supersonic wind tunnel, the white lines are the condensations formed in the test chamber due to flow expansion. Why are the condensations so ...
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What do the components of a shockwave's visual artefacts represent?

On a recent flight, I was able to observe visual artefacts over the wing (Boeing 767-300 in cruise). You can see them in the image below; they look like creases in a surface. They moved forwards and ...
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Why does this shockwave not touch the body that creates it?

In the shock wave of the next image (in a blunt body) Why the wavefront is in front of the object? It does not assume that if the object travels faster than the speed of sound wave front should be ...
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Can a flow which is initially supersonic, become subsonic without a shock wave?

I am doing my college project in which air is first accelerated to supersonic conditions in a nozzle. Then it is added into slow moving subsonic air. I see that my flow becomes supersonic and then ...
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Reason behind formation of Mach rings [duplicate]

At night, some jet aircraft like Mirage 2000 leave a trail of discs behind in their jet, these are also known as Mach rings or Mach diamonds. How are they formed and what atmospheric conditions ...
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How does a wing mounted jet engine on a supersonic airplane prevent the interference in the flow due to Shock? [duplicate]

Wing mounted jet engines face the free stream at Mach number 1 or above, and they work perfectly for Mach numbers below 1 as well, even though the free stream characteristics change a lot after Mach 1....