# Calculating Pressure Distribution in a Nozzle for Abaqus

Hey all,

So I have a small convergent nozzle that I'm modelling in Abaqus and I'm wondering how I could work out the pressure distribution so I can apply the correct load. The problem is I only know the pressure being fed to it by air compressor. Is there a way to use Bernoulli s or some other method ? Can I make assumptions for the velocities or maybe even find general info on compressor and assume same?

Also considering the size of the nozzle is only about 30mm would I be as well to set the load as a uniform pressure?

Thanks!

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Gold Member
You could get a decent estimate using conservation of mass and Bernoulli's equation.

You could get a decent estimate using conservation of mass and Bernoulli's equation.
Thanks for the reply. How would I go about doing this as I only know the pressure is 15 bar?

Gold Member
Do you know how fast it is moving at 15 bar?

Do you know how fast it is moving at 15 bar?
No I don't although I could probably take a value from a compressor data sheet and assume the same?

Gold Member
The first think you need to do is figure out whether the flow can be assumed incompressible or not. If it is incompressible, you can just use conservation of mass and Bernoulli's equation. If it is compressible, you will have to make a few assumptions.

If it is compressible, it's probably easiest if the incoming speed is slow enough that you can treat it as zero. If it is incompressible, the mass is easier but you will need to figure out what flow rate you have moving through the system so you can convert that to a velocity and then a pressure using the Bernoulli equation. Even then, it's just an estimate since you are going to be ignoring the effects of viscosity.

The first think you need to do is figure out whether the flow can be assumed incompressible or not. If it is incompressible, you can just use conservation of mass and Bernoulli's equation. If it is compressible, you will have to make a few assumptions.

If it is compressible, it's probably easiest if the incoming speed is slow enough that you can treat it as zero. If it is incompressible, the mass is easier but you will need to figure out what flow rate you have moving through the system so you can convert that to a velocity and then a pressure using the Bernoulli equation. Even then, it's just an estimate since you are going to be ignoring the effects of viscosity.
Hey, thanks for the help. I got a CFM value from the compressor data sheet of 5.8. I converted it to 0.002454 m3/sec and then that to 195 m/s by dividing by the csa. Are my maths right here? That would give a mach of 0.57 and so it must be compressible right?

Thanks again.

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