pressure drop in the pipe

mike.mm · February 5, 2011, 04:40

Hi Friends,

I am very new to fluent software and just now started learning fluent...

In that i have one doubt i have modeled incompressible flow through horizontal pipe.
1) i have given velocity inlet and pressure outlet as my boundary conditions.how to calculate pressure drop of fluid through pipe ?

2) In the above problem, if i know pressure and velocity of inlet fluid and i want to calculate pressure drop of the fluid. In this case how should i specify these specify my boundary conditions and how calculate pressure drop?
Please clear my doubt ..Thanks in advance...
with regards
mike.

Amir · February 5, 2011, 09:44

Hi mike,
1) after you solved for flow field , you can plot pressure for example in centerline or also save that data . (in fully developed flow it should be linear)
2) in this case you can set exit as outflow , and allow flow to reach it's realistic pressure value . pressure drop calculation is as above.

abdul moqeet · February 7, 2011, 00:26

Hi Amir,
I am also new to Fluent
i am to model the air flow through a diagonal rectangular pipe, only the velocity of the air at outlet is known, as there is a suction fan at the outlet. plz guide what exact boundary conditions should i use???

with regards

Abdul Moqeet

Amir · February 7, 2011, 03:40

Hi abdul,
some years ago I faced the same problem and I handled that with this tip:
you know velocity profile at the exit as a function of space , first you can use velocity inlet but with negative velocity magnitudes at the outlet !
after some iterations and convergence, you can find pressure change near outlet and change boundary condition to exhaust fan. by this you will have compatible boundary condition.

abdul moqeet · February 7, 2011, 05:16

Dear Amir,

Many thanks for your response
please elaborate it a bit more as i am a textile engr by profession. so naturally i am not used to the terms. i have perceived the sense you wanted to communicate, to a good extent, but elaborate more if you can.

regards

Amir · February 7, 2011, 08:58

Dear abdul,
as usual we can set velocity at inlet but we can't at outlet. by setting pressure there, velocity profile will be found. but in this cases you can use a trick. we can assume outlet boundary as an inlet one but with negative velocity magnitudes.
after using this method and solving for flow field, you can change your boundary conditions to realistic ones, there you need pressure drop for example, you can use the result of first stage here.

-abdul- · February 7, 2011, 11:31

Many thanks dear
i got your point.....

thanks again

Abdul Moqeet

February 5, 2011, 04:40	pressure drop in the pipe	#1
mike.mm New Member mike Join Date: Feb 2011 Posts: 4 Rep Power: 15	Hi Friends, I am very new to fluent software and just now started learning fluent... In that i have one doubt i have modeled incompressible flow through horizontal pipe. 1) i have given velocity inlet and pressure outlet as my boundary conditions.how to calculate pressure drop of fluid through pipe ? 2) In the above problem, if i know pressure and velocity of inlet fluid and i want to calculate pressure drop of the fluid. In this case how should i specify these specify my boundary conditions and how calculate pressure drop? Please clear my doubt ..Thanks in advance... with regards mike.

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February 5, 2011, 09:44		#2
Amir Senior Member Amir Join Date: May 2009 Location: Montreal, QC Posts: 735 Blog Entries: 1 Rep Power: 23	Hi mike, 1) after you solved for flow field , you can plot pressure for example in centerline or also save that data . (in fully developed flow it should be linear) 2) in this case you can set exit as outflow , and allow flow to reach it's realistic pressure value . pressure drop calculation is as above.

February 7, 2011, 00:26		#3
abdul moqeet New Member abdul moqeet hai Join Date: Dec 2010 Posts: 17 Rep Power: 16	Hi Amir, I am also new to Fluent i am to model the air flow through a diagonal rectangular pipe, only the velocity of the air at outlet is known, as there is a suction fan at the outlet. plz guide what exact boundary conditions should i use??? with regards Abdul Moqeet

February 7, 2011, 03:40		#4
Amir Senior Member Amir Join Date: May 2009 Location: Montreal, QC Posts: 735 Blog Entries: 1 Rep Power: 23	Hi abdul, some years ago I faced the same problem and I handled that with this tip: you know velocity profile at the exit as a function of space , first you can use velocity inlet but with negative velocity magnitudes at the outlet ! after some iterations and convergence, you can find pressure change near outlet and change boundary condition to exhaust fan. by this you will have compatible boundary condition.

February 7, 2011, 05:16		#5
abdul moqeet New Member abdul moqeet hai Join Date: Dec 2010 Posts: 17 Rep Power: 16	Dear Amir, Many thanks for your response please elaborate it a bit more as i am a textile engr by profession. so naturally i am not used to the terms. i have perceived the sense you wanted to communicate, to a good extent, but elaborate more if you can. regards

February 7, 2011, 08:58		#6
Amir Senior Member Amir Join Date: May 2009 Location: Montreal, QC Posts: 735 Blog Entries: 1 Rep Power: 23	Dear abdul, as usual we can set velocity at inlet but we can't at outlet. by setting pressure there, velocity profile will be found. but in this cases you can use a trick. we can assume outlet boundary as an inlet one but with negative velocity magnitudes. after using this method and solving for flow field, you can change your boundary conditions to realistic ones, there you need pressure drop for example, you can use the result of first stage here.

February 7, 2011, 11:31		#7
-abdul- New Member Join Date: Feb 2011 Posts: 1 Rep Power: 0	Many thanks dear i got your point..... thanks again Abdul Moqeet