[frafole]

Hi,
I'm simulating a convegent divergent nozzle in fluent with air. I've noticed that the AreaAvarage pressure in inlet changes when I change the dimensions of the nozzle, even if I set as BC ambient pressure inlet; why does that happen? Otherwise I'm searching for the minor pressure drops from inlet to outlet, and I don't undestand why pressure drops seems that have more than one minimum value if I modify the length of the nozzle without changing the angles, but in theory pressure drops should be linear. Does anyone know what I'm probably missing?
thank you very much.

[ssixr]

Originally Posted by frafole

Hi,
I'm simulating a convegent divergent nozzle in fluent with air. I've noticed that the AreaAvarage pressure in inlet changes when I change the dimensions of the nozzle, even if I set as BC ambient pressure inlet; why does that happen? Otherwise I'm searching for the minor pressure drops from inlet to outlet, and I don't undestand why pressure drops seems that have more than one minimum value if I modify the length of the nozzle without changing the angles, but in theory pressure drops should be linear. Does anyone know what I'm probably missing?
thank you very much.

Hi frafole,
Area Average concept is based on surface area...please check fluent documentation.

[frafole]

Originally Posted by ssixr

Hi frafole,
Area Average concept is based on surface area...please check fluent documentation.

Yes, it makes a surface integral of the pressure, so the results doesen't depend on the size of the surface but its a mean pressure.

[ssixr]

Originally Posted by frafole

Yes, it makes a surface integral of the pressure, so the results doesen't depend on the size of the surface but its a mean pressure.

Hi,
The area-weighted average of a quantity is computed by dividing the summation of the product of the selected field variable and facet area by the total area of the surface..
check this link http://aerojet.engr.ucdavis.edu/flue...g/node1199.htm


sudhir

[frafole]

Originally Posted by ssixr

Hi,
The area-weighted average of a quantity is computed by dividing the summation of the product of the selected field variable and facet area by the total area of the surface..
check this link http://aerojet.engr.ucdavis.edu/flue...g/node1199.htm


sudhir

Ok, so in your opinion how can I do to calcolate the mean absolute pressure on a surface that is independent from its size?
Thank you for your help.

[ssixr]

Node or mass weighted average would be a better choice in my opinion. Hope it helps..

[frafole]

Originally Posted by ssixr

Node or mass weighted average would be a better choice in my opinion. Hope it helps..

I just tired with both methods but there is a difference of 7Pa from the results of area avarege method so my problem persists...

[ssixr]

Originally Posted by frafole

I just tired with both methods but there is a difference of 7Pa from the results of area avarege method so my problem persists...

are you changing geometry of inlet?

sudhir