Fluid analysis, potential energy

tkor · April 20, 2023, 20:43

No change in total pressure due to positional energy can be confirmed.

・Water flows through straight pipes from a height of 1 meter.
・The water is flowing in the direction of gravity.
・The diameter does not change.
・Boundary conditions are inlet total pressure and outlet mass flow
・Pipe is frictionless

At this time, I think that the total pressure at the outlet side will increase by the amount of the positional energy at the inlet according to Bernoulli's principle, but the total pressure does not increase as a result of the analysis.
Also, I've tried changing the gravitational acceleration in various ways, but there is no change in the total pressure at the outlet.

Is there a problem with the boundary conditions?
Please give me some advice.

NickFL · April 21, 2023, 04:03

In Fluent, gravity doesn't show up in the potential energy or pressure terms. It is treated on the source side. You can Post-Process some terms to visualize the potential energy and then you can see that everything follows.

This is the typical approach used in CFD. Look into the textbooks for a more detailed explanation.

April 20, 2023, 20:43	Fluid analysis, potential energy	#1
tkor New Member tkor Join Date: Apr 2023 Posts: 9 Rep Power: 3	No change in total pressure due to positional energy can be confirmed. ・Water flows through straight pipes from a height of 1 meter. ・The water is flowing in the direction of gravity. ・The diameter does not change. ・Boundary conditions are inlet total pressure and outlet mass flow ・Pipe is frictionless At this time, I think that the total pressure at the outlet side will increase by the amount of the positional energy at the inlet according to Bernoulli's principle, but the total pressure does not increase as a result of the analysis. Also, I've tried changing the gravitational acceleration in various ways, but there is no change in the total pressure at the outlet. Is there a problem with the boundary conditions? Please give me some advice.

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April 21, 2023, 04:03		#2
NickFL Senior Member Join Date: Jun 2009 Location: Technische Universität Chemnitz Posts: 107 Rep Power: 17	In Fluent, gravity doesn't show up in the potential energy or pressure terms. It is treated on the source side. You can Post-Process some terms to visualize the potential energy and then you can see that everything follows. This is the typical approach used in CFD. Look into the textbooks for a more detailed explanation.