Suction modeling

hamid1 · January 2, 2011, 15:55

Hi

I am modeling a suction inside a pipe, suction happens via a narrower pipe which is located inside a wider pipe,

Could anybody let me know if suction could be modeled through Fluent and if so, then which kind of B.C. should be used, is pressure outlet is ok, and should I put a negative amount for that (the pressure outlet)?

what is the maximum amount for Reynolds that I can use laminar flow inside the pipe, and if I am more than that threshold but less than 2300 (critical amount for turbulant regime inside a pipe), which model should I use, laminar or Turbulant?

thanks alot i advance

hamid1 · January 3, 2011, 18:58

please, could anybody reply me, it is very important for me, thanks all

ComputerGuy · January 3, 2011, 22:21

Suction is simply a lower local pressure condition (there's nothing special about outward flow or inward flow).

As such, using a pressure outlet boundary condition is fine. The "inlet" condition can be pressure as well; setting it to 0 Pa and the outlet to -100 Pa (for example) will cause an outflow (suction).

If you have a Re < 2100, you can be reasonably certain that the flow is laminar.

ComputerGuy

hamid1 · January 5, 2011, 02:52

Thanks ComputerGuy, it helped me to be more sure about my work, thanks again...

January 2, 2011, 15:55	Suction modeling	#1
hamid1 Senior Member hamid Join Date: Nov 2010 Posts: 185 Rep Power: 16	Hi I am modeling a suction inside a pipe, suction happens via a narrower pipe which is located inside a wider pipe, Could anybody let me know if suction could be modeled through Fluent and if so, then which kind of B.C. should be used, is pressure outlet is ok, and should I put a negative amount for that (the pressure outlet)? what is the maximum amount for Reynolds that I can use laminar flow inside the pipe, and if I am more than that threshold but less than 2300 (critical amount for turbulant regime inside a pipe), which model should I use, laminar or Turbulant? thanks alot i advance

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January 3, 2011, 18:58		#2
hamid1 Senior Member hamid Join Date: Nov 2010 Posts: 185 Rep Power: 16	please, could anybody reply me, it is very important for me, thanks all

January 3, 2011, 22:21		#3
ComputerGuy Senior Member Real Name :) Join Date: Jan 2010 Location: United States Posts: 192 Rep Power: 16	Suction is simply a lower local pressure condition (there's nothing special about outward flow or inward flow). As such, using a pressure outlet boundary condition is fine. The "inlet" condition can be pressure as well; setting it to 0 Pa and the outlet to -100 Pa (for example) will cause an outflow (suction). If you have a Re < 2100, you can be reasonably certain that the flow is laminar. ComputerGuy

January 5, 2011, 02:52		#4
hamid1 Senior Member hamid Join Date: Nov 2010 Posts: 185 Rep Power: 16	Thanks ComputerGuy, it helped me to be more sure about my work, thanks again...