Effect of gravity force in a pipe flow

novice · July 14, 2010, 02:23

Dear All,

It is a very basic question but very important one for me. Does the gravity force has any effect on a flow through a cyllindrical pipe??

Thanks in advance

Novice

MacWnc · July 14, 2010, 03:49

In my opinion it has effect on flow for vertical pipe or horizontal pipe with great diameter, also the gravity force depends on density of the fluid.

novice · July 14, 2010, 03:56

Hi MacWnc,

Thanks for the reply. If the fluid is water (incompressible) will there be any effect of the gravitational force on the flow.

Regards

MacWnc · July 14, 2010, 04:03

Water has great density , so it affect on flow. Your duct is vertical or horizontal? what is the diameter of it?

novice · July 14, 2010, 04:21

Hi MacWnc,

The pipe diameter different in different cases. It varies from 48" (1220 mm) to 10" (254 mm). The pipe has a 90° elbow. One case the flow coming from the downwars then enters into an elbow and go toward right side, that means the flow come from a vertical pipe enters into an elbow then enters in to a horizontal pipe (like 6:15 in a clock). and in one other case the pipe has an elbow but it is completely horizontal. In these two cases will the Gravitational force has any effect on the flow??

Thanks again.

MacWnc · July 14, 2010, 04:32

You should turn on the gravity for every case. It does not increase computational time, so dont bother yourself anymore. the effect of gravity will be greater in horizontal pipe.

novice · July 14, 2010, 05:28

Hi MacWnc,
I am activating the gravity in all my simulations. But, irrespective of the fluent simulation, in general i would like to know whether the gravitational force has an effect on the flow through a pipe. If you have any study material on this aspect, can you please forward to me.
Regards

rgd · September 13, 2014, 00:47

Dear all,

I am simulating the maldistribution through a distributor (with multiple outlets) & I am trying to find the effect of gravity on both orientations: horizontal & vertical. I turned on the gravity in y-direction for horizontal & in z-direction for vertical. But there seems to be no difference at all in my simulations, both are identical!
Nonetheless, the reference I am using states otherwise, also common sense dictates that the simulation in the vertical direction should have less maldistribution.
So what am I forgetting here? is there any other parameter I need to enter in Fluent?

P.S. As a trial I activated the 'Specified Operating Density' option in the 'Operating Conditions' window, under the 'Boundary Conditions', and I set it to the density of my working fluid: water (when I simulate one phase only) & water-vapor (when I am simulating 2 phases)

Thota · May 29, 2015, 11:02

I think body forces are critical in your case. Try changing the under-relaxation factors and then check the results.

July 14, 2010, 02:23	Effect of gravity force in a pipe flow	#1
novice Member novice Join Date: Nov 2009 Posts: 33 Rep Power: 16	Dear All, It is a very basic question but very important one for me. Does the gravity force has any effect on a flow through a cyllindrical pipe?? Thanks in advance Novice

July 14, 2010, 04:21		#5
novice Member novice Join Date: Nov 2009 Posts: 33 Rep Power: 16	Hi MacWnc, The pipe diameter different in different cases. It varies from 48" (1220 mm) to 10" (254 mm). The pipe has a 90° elbow. One case the flow coming from the downwars then enters into an elbow and go toward right side, that means the flow come from a vertical pipe enters into an elbow then enters in to a horizontal pipe (like 6:15 in a clock). and in one other case the pipe has an elbow but it is completely horizontal. In these two cases will the Gravitational force has any effect on the flow?? Thanks again. rgd likes this.

July 14, 2010, 05:28		#7
novice Member novice Join Date: Nov 2009 Posts: 33 Rep Power: 16	Hi MacWnc, I am activating the gravity in all my simulations. But, irrespective of the fluent simulation, in general i would like to know whether the gravitational force has an effect on the flow through a pipe. If you have any study material on this aspect, can you please forward to me. Regards rgd likes this.

September 13, 2014, 00:47	Effect of gravity missing!	#8
rgd New Member Join Date: Dec 2012 Posts: 24 Rep Power: 13	Dear all, I am simulating the maldistribution through a distributor (with multiple outlets) & I am trying to find the effect of gravity on both orientations: horizontal & vertical. I turned on the gravity in y-direction for horizontal & in z-direction for vertical. But there seems to be no difference at all in my simulations, both are identical! Nonetheless, the reference I am using states otherwise, also common sense dictates that the simulation in the vertical direction should have less maldistribution. So what am I forgetting here? is there any other parameter I need to enter in Fluent? P.S. As a trial I activated the 'Specified Operating Density' option in the 'Operating Conditions' window, under the 'Boundary Conditions', and I set it to the density of my working fluid: water (when I simulate one phase only) & water-vapor (when I am simulating 2 phases)

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July 14, 2010, 03:49		#2
MacWnc New Member Maciej Join Date: Dec 2009 Posts: 6 Rep Power: 16	In my opinion it has effect on flow for vertical pipe or horizontal pipe with great diameter, also the gravity force depends on density of the fluid.

July 14, 2010, 03:56		#3
novice Member novice Join Date: Nov 2009 Posts: 33 Rep Power: 16	Hi MacWnc, Thanks for the reply. If the fluid is water (incompressible) will there be any effect of the gravitational force on the flow. Regards

July 14, 2010, 04:03		#4
MacWnc New Member Maciej Join Date: Dec 2009 Posts: 6 Rep Power: 16	Water has great density , so it affect on flow. Your duct is vertical or horizontal? what is the diameter of it?

July 14, 2010, 04:32		#6
MacWnc New Member Maciej Join Date: Dec 2009 Posts: 6 Rep Power: 16	You should turn on the gravity for every case. It does not increase computational time, so dont bother yourself anymore. the effect of gravity will be greater in horizontal pipe.

May 29, 2015, 11:02		#9
Thota New Member Thota Join Date: Apr 2014 Posts: 6 Rep Power: 12	I think body forces are critical in your case. Try changing the under-relaxation factors and then check the results.