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# Simulate Gas under pressure inside tube of structural simulation

Experimenter

Hello,

I am performing Structural analysis of a bracket which holds a tube and the tube carries a gas which is under pressure.

In my current setup, i have a hollow tube which must be carrying gas at certain pressure.

Could anyone please help how I can simulate the gas flowing in the tube for my structural analysis?

Thanks & Regards,

Krishna

3 REPLIES

# Re: Simulate Gas under pressure inside tube of structural simulation

Solution Partner Phenom

Hello!,

Well, the simplest FE analysis is to apply a pressure load to the tube and perform a linear static analysis of the full structure considering the gas pressure constant. Next you can study dynamic analysis to compute the transient response of the structure, in case you know the dynamic nature of the gas excitation (ie, perform a Dynamic Time History Analysis).

The Dynamic analysis could be linear or nonlinear, depending of the level of the excitation, if causing large displacements effect (geometric nonlinearity) or material nonlinearities. If the structural behaviour is linear, from the point of view of the dynamic analysis is preferible to work in the frequency domain instead time domain due to performance issues.

Here you are a tube excited dynamically in the time domain under an internal variable pressure:

And here you are the dynamic response performing a modal frequency dynamic response analysis using NX NASTRAN (SOL112):

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/

# Re: Simulate Gas under pressure inside tube of structural simulation

Experimenter
Hello Blas_Molero,

Thanks a bunch for your reply. I am in fact trying to find out frequencies of the fuel lines in various modes. Here the fuel is a CNG which is passing through the lines at a pressure of around 25MPa.

Like you had suggested for linear dynamic response, I selected SOL 112 and constrained the brackets which essentially holds the tube in its place, provided the necessary contacts and applied the appropriate pressure on the inner side of the tube. But how do I add time domain under an internal pressure?

Best regards,
Krishna

# Re: Simulate Gas under pressure inside tube of structural simulation

Solution Partner Phenom

Hello!,

You have to know the transient nature of the load, once you know this value (in geneal your contractor will give you this data) simply enter in NX AdvSim and assoacit the time curve to the pressure load.

Here you are a few different types of transient dynamic (vs. time) excitations:

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director
IBERISA • 48004 BILBAO (SPAIN)
WEB: http://www.iberisa.com
Blog Femap-NX Nastran: http://iberisa.wordpress.com/