[andrew-c]

A simple clarification question -

In a 2D axisymmetric case, the x-axis is the axis of symmetry. Then, applying gravity in the +x or -x direction simulates a vertically-oriented tube (gravity acts axially).

Does y-directed gravity then simulate a horizontally-oriented tube? (This makes the most sense to me, but then the domain is not exactly symmetric).

Or, would it simulate a tube with gravity always directed radially/towards the center? (This would preserve symmetry, but I can't imagine why this would be useful).

If anyone can confirm that y-directed gravity in 2D axisymmetric case simulates a horizontally-oriented tube, I'd greatly appreciate it. Thanks!

[PacMan]

Fluent requires that the axis of symmetry is on the x-axis. In this case, no fluid can cross the symmetry axis, and no fluid is expected to move in the tangential direction. Therefore the gravity expressed in the y-direction would be the same as expressing it in the radial direction and is not the same as simulating a horizontally oriented tube.

If your problem contains just one phase, check if gravity can be neglected. If gravity is important, do a 3D simulation.

[A.Rahimi]

i have a quastion now
i simulating a vertical pipe that flow go in from top and go out from botton
in aximmetric i must draw it horizontal in this case flow go in from left and go out from right
so my quastion is i must put gravity +9.8 or -9.8?
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[PacMan]

If fluid flows from top to bottom (parallel to the gravity vector), when simulating, the fluid vector points in the positive direction of the x-axis; therefore, you should set the gravity vector pointing in the positive x-direction.