Guide to Supersonic Drag Increase in Nose Cones

In summary, at supersonic speeds, the drag increases on objects due to the earlier separation of the boundary layer. The blunt shaped object increases the drag due to the earlier separation of the shock wave.
  • #1
Hi
Can anyone explain in detail about drag increase in supersonic speed


Why and how drag increases in Blunt shape nose cone to compare with Sharp nose cone at supersonic speed?


Ryan
 
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  • #2
Well...just to clarify, do the two cones have the same diameter? Because even for subsonic flows, a blunt shaped object would increase the drag due to the earlier separation of the boundary layer.
 
  • #3
I believe one factor is due to the shock wave disconnecting from the body for the case of the blunt body.
 
  • #4
Explain in detail? No, you will need a textbook for the that. What I will tell you is that at super sonic flows nothing becomes intuitive anymore. Nozzle become diffusers, diffusers become nozzle, and the aerodynamic of most geometry completely change. Supersonic flows are a petty neat subject but the concepts that follow them take some time and work to comprehend.
 
  • #5
Topher925 said:
Explain in detail? No, you will need a textbook for the that. What I will tell you is that at super sonic flows nothing becomes intuitive anymore. Nozzle become diffusers, diffusers become nozzle, and the aerodynamic of most geometry completely change. Supersonic flows are a petty neat subject but the concepts that follow them take some time and work to comprehend.

I still can't intuitively grasp how a supersonic flow works in a converging-diverging nozzle works.

After the choke point, the area is increasing AND the velocity is increasing. To top it all of, the density is decreasing in a flow that is going fast enough to be considered compressible...sigh..
 
  • #6
mfc5200 said:
I still can't intuitively grasp how a supersonic flow works in a converging-diverging nozzle works.

After the choke point, the area is increasing AND the velocity is increasing. To top it all of, the density is decreasing in a flow that is going fast enough to be considered compressible...sigh..



It can be explained through the manipulation of the mass conservation equation:

density*velocity*area = constant

Taking the derivative and manipulating it to get d density/density + d velocity/velocity + d area/area = 0, and using the definition of the speed of sound/Mach number...you end up with this equation:

d velocity/velocity * (mach number^2 - 1) = d area/area

This is known as the area-velocity relationship. So as you can see, for mach numbers less than 1, you get a negative sign for the value, thereby getting that relationship used in INcompressible flow where velocity slows down when area goes up, and vice versa.

When you start to go above Mach 1, the sign becomes positive, and both area and velocity essentially change in the same direction.
 
  • #7
mfc5200 said:
I still can't intuitively grasp how a supersonic flow works in a converging-diverging nozzle works.

After the choke point, the area is increasing AND the velocity is increasing. To top it all of, the density is decreasing in a flow that is going fast enough to be considered compressible...sigh..

Why should you intuitively grasp supersonic flow? It's not something in your everyday tactile experience!

Do you have an intuitive understanding of low reynolds flow? Nope. You are way too large to experience 'atoms' of air hitting you. You can only feel a continuum.

Your 'intuition' will come through understanding of the mathematics of the flow.
 

1. What is supersonic drag and why is it important?

Supersonic drag is the resistance force experienced by an object traveling at supersonic speeds. It is important because it can significantly affect the performance and efficiency of a supersonic vehicle, such as a missile or spacecraft.

2. How does the shape of a nose cone affect supersonic drag?

The shape of a nose cone plays a crucial role in determining the amount of supersonic drag experienced by a vehicle. A streamlined, pointed nose cone can significantly reduce drag compared to a blunt, flat nose cone.

3. What factors contribute to supersonic drag increase in nose cones?

There are several factors that can contribute to an increase in supersonic drag in nose cones, including the shape, angle of attack, and surface roughness of the cone. Other factors such as shock waves and boundary layer separation can also play a role.

4. How can the guide to supersonic drag increase in nose cones be used in practical applications?

The guide can be used to design more efficient nose cones for supersonic vehicles, such as missiles and spacecraft, by providing information on the factors that affect drag and how to minimize it. It can also be used for research purposes to better understand the physics of supersonic drag.

5. Are there any limitations to the guide's applicability?

Yes, the guide is primarily focused on nose cones for supersonic vehicles and may not be directly applicable to other objects or scenarios. Additionally, the guide is based on theoretical and experimental data, so variations in real-world conditions may affect its accuracy.

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