Fluid flow through a pipe - Conservation of mass and/or momentum?

In summary, the conversation discusses the use of conservation of momentum and conservation of mass in calculating the density of air in a nozzle. The speaker notes that while conservation of mass yields a value of 1060, conservation of momentum results in a different value of 1004. The discrepancy is attributed to the acceleration of the fluid in the nozzle, which causes a decrease in density despite a constant mass flow rate.
  • #1
theBEAST
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0

Homework Statement


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The Attempt at a Solution


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So first I found the density of the air coming in and going out. Next I used conservation of momentum with two forces caused by the pressures at the entrance and the exit of the nozzle.

I end up getting 1004 which is not the same as 1060. If I just use conservation of mass so ρVAout=ρVAin I get exactly 1060. So why is it that conservation of momentum does not work in this scenario?
 
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  • #2
The nozzle is accelerating the flow of the fluid through the restriction. The mass flow into the nozzle is the same as the mass flow out, but the velocity has increased while the density decreases.
 

Related to Fluid flow through a pipe - Conservation of mass and/or momentum?

1. What is fluid flow through a pipe?

Fluid flow through a pipe refers to the movement of a fluid, such as water or oil, through a closed system of pipes. This can occur in a variety of scenarios, such as in plumbing systems, industrial processes, or transportation of liquids.

2. What is conservation of mass in fluid flow through a pipe?

Conservation of mass in fluid flow through a pipe is a fundamental principle that states that the mass of fluid entering a pipe must equal the mass of fluid exiting the pipe. This means that the total amount of fluid in the system remains constant, even as it flows through different sections of the pipe.

3. How is conservation of mass related to fluid flow pressure?

In fluid flow through a pipe, conservation of mass is related to fluid flow pressure through the continuity equation. This equation states that the product of fluid density, cross-sectional area, and flow velocity must remain constant at any point in the pipe. This means that as the cross-sectional area decreases, the velocity of the fluid must increase, resulting in a decrease in pressure.

4. What is conservation of momentum in fluid flow through a pipe?

Conservation of momentum in fluid flow through a pipe states that the total momentum of the fluid entering the pipe must equal the total momentum of the fluid exiting the pipe. This means that the force exerted by the fluid on the walls of the pipe must be equal at all points along the pipe, resulting in a steady flow.

5. How does the shape and size of a pipe affect fluid flow?

The shape and size of a pipe can significantly affect fluid flow. A smaller cross-sectional area will result in a higher flow velocity and therefore a decrease in pressure, while a larger cross-sectional area will result in a slower flow velocity and an increase in pressure. The shape of the pipe can also impact the flow pattern and the amount of friction between the fluid and the pipe walls, which can affect the overall flow rate.

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