[novic]

Dear fellow members,

I have some questions regarding the static pressure calculation in Fluent. in general (theoretically), the Static pressure decreases by increasing the flow rate. But in my simulation using FLUENT, the static pressure values are increasing with the increase of flow rate. Is FLUENT uses a different method to calculate these values or is there something wrong with my simulation??
My simulation case is a "U" shaped pipe section, which has elbow pipe extensions on the top of the "U".

I appreciate your valuable inputs, thanks in advance.

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Novic

[LuckyTran]

I think you are confusing static pressure with static pressure drop. Pressure drop increases with increasing flow rate.

But if you have fixed pressure at the outlet, then the local static pressure would have to increase with increasing flowrate to satisfy the increasing pressure drop. criterion.

On the other hand, if you have a fixed pressure at the inlet, then the local static pressure would have to decrease at each cell with increasing flow rate.

[novic]

Originally Posted by LuckyTran

I think you are confusing static pressure with static pressure drop. Pressure drop increases with increasing flow rate.

But if you have fixed pressure at the outlet, then the local static pressure would have to increase with increasing flowrate to satisfy the increasing pressure drop. criterion.

On the other hand, if you have a fixed pressure at the inlet, then the local static pressure would have to decrease at each cell with increasing flow rate.

Thanks LuckyTran for your response.
My simulation settings are: velocity inlet with a constant velocity, and a gauge pressure '0' Pa. Outlet as Pressure outlet with gauge pressure '0' Pa. The operating pressure is 101325 Pa.
If I understood you correctly, to get the values of static pressure at a particular point, I have to subtract the values given by FLUENT from the Operating pressure. Please correct me if I am wrong.

Regards,

Novic

[LuckyTran]

If you have a velocity inlet with outlet pressure then yes static pressure inside the domain would have to increase with increasing flow rate.

Originally Posted by novic

If I understood you correctly, to get the values of static pressure at a particular point, I have to subtract the values given by FLUENT from the Operating pressure. Please correct me if I am wrong.

Regards,

Novic

I did not mention the operating pressure at all. But the values given by Fluent are the gauge pressures and you need to ADD the values given by Fluent with the operating pressure to see the absolute pressure.

[novic]

Originally Posted by LuckyTran

If you have a velocity inlet with outlet pressure then yes static pressure inside the domain would have to increase with increasing flow rate.



I did not mention the operating pressure at all. But the values given by Fluent are the gauge pressures and you need to ADD the values given by Fluent with the operating pressure to see the absolute pressure.

Thanks again for a quick response.
For calculating the total pressure, do I need to do the same as for the static pressure calculation.

Thanks in advance.

[LuckyTran]

Yes you must add the same for total pressure.