# Where Does the Normal Shock Occur in a Supersonic CD-Nozzle?

• santasanjai
In summary, a Convergent-Divergent passage with supersonic flow upstream and downstream will have a normal shock in the diverging section between points 2 and 3. This is because the flow decelerates in this section, leading to an increase in pressure, density, and temperature."
santasanjai

## Homework Statement

Hi everybody! I have a question about this type of flow. I have a Convergent divergent passage, with supersonic flow upstream and downstream, the flow iside of it is unknowm. The question is that , knowing that one normal shock occurs within the canal, either in the convergent or the divergent part, which one is the right answer? I know it happens in the convergent part but why? I know that decelerating the supersonic flow entering the convergent part would cause a rise in pressure, density and temperature, but I´m not able to motivate more than that. Anybody can help me? The convergent part is between 1 and 2, the divergent between 2 and 3.

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Hello! Thank you for your question. First of all, it is important to understand the basics of supersonic flow and the role of shocks in it. In supersonic flow, the Mach number (ratio of flow velocity to the speed of sound) is greater than 1. This means that the flow is moving faster than the speed of sound and therefore, the flow field is characterized by high velocities and high temperatures.

In a Convergent-Divergent (CD) passage, the flow is initially supersonic at the inlet (point 1) and then it passes through a converging section (between 1 and 2) which further accelerates the flow, leading to an even higher Mach number. The flow then enters a diverging section (between 2 and 3) where it decelerates and the Mach number decreases. The flow then exits the passage at point 3.

Now, coming to your question about the occurrence of a normal shock in the CD passage. A normal shock is a type of shock wave that occurs when a supersonic flow is decelerated to a subsonic flow. In the CD passage, the flow decelerates in the diverging section (between 2 and 3) and this is where the normal shock will occur. This is because the flow is moving from a wider to a narrower section, which causes a decrease in flow velocity. This decrease in velocity leads to an increase in pressure, density and temperature, as you correctly mentioned.

In summary, the normal shock occurs in the diverging section of the CD passage because the flow is decelerated from supersonic to subsonic speeds. I hope this helps to clarify your question. If you have any further doubts, please let me know.

## 1. What is a Supersonic CD-nozzle?

A Supersonic CD-nozzle is a type of nozzle used in supersonic wind tunnels to accelerate the flow of gas to supersonic speeds. It is shaped like a cone with a curved profile and a sharp exit edge, designed to maximize the expansion of the gas and achieve supersonic velocities.

## 2. How does a Supersonic CD-nozzle work?

The Supersonic CD-nozzle works by taking in a high pressure gas and expanding it through a converging-diverging section. This causes the gas to accelerate and reach supersonic speeds. The curved profile of the nozzle helps to efficiently expand the gas and achieve smooth flow.

## 3. What is the purpose of a Supersonic CD-nozzle?

The main purpose of a Supersonic CD-nozzle is to accelerate the flow of gas to supersonic speeds in supersonic wind tunnels. This allows scientists and engineers to study the behavior of objects and materials at high speeds, which is important for designing and testing supersonic aircraft and other advanced technologies.

## 4. What are the advantages of using a Supersonic CD-nozzle?

The advantages of using a Supersonic CD-nozzle include its ability to efficiently accelerate gas to supersonic speeds, its simple and compact design, and its ability to produce a uniform and stable supersonic flow. It is also relatively easy to manufacture and can be used in a wide range of supersonic testing applications.

## 5. Are there any limitations or drawbacks of using a Supersonic CD-nozzle?

One limitation of using a Supersonic CD-nozzle is that it is only suitable for accelerating gas to supersonic speeds, and cannot be used for subsonic or hypersonic speeds. Additionally, the design and performance of the nozzle can be affected by factors such as temperature, pressure, and turbulence, which may require adjustments or modifications for different testing conditions.

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