Reverse flow

- October 8, 2018 at 4:42 am
  
  srnayak97
  Subscriber
  
  Hello everyone. I am doing a model study for reverse flow (sinusoidal velocity inlet) through a pipe. So my inlet and outlet changes constantly. Is it the right way to specify inlet boundary with a udf and outlet as a constant pressure boundary?
  
  Thank you
  
  regards
  
  Soumya Ranjan Nayak
- October 8, 2018 at 5:31 am
  
  seeta gunti
  Ansys Employee
  
  Hello Soumya,
  
  You mentioned that your inlet and outlet conditions are not constant so you need to provide the inlet as either profile or UDF. Providing an UDF for the inlet is an appropriate approach. Please note that by giving outlet as constant pressure boundary, you are fixing the pressure as constant which may not be right in your case.
  
  Regards,
  
  Seeta
- October 8, 2018 at 6:14 am
  
  srnayak97
  Subscriber
  
  Hello Seeta,
  
  I am also confused about outlet boundary condition. Flow reversal means my outlet and inlet changes position after each half cycle. I do not think Constant pressure outlet is a problem. There can be a necessary pressure oscillation at the inlet to take care of the flow direction. Anyway, what is your suggestion on outlet BC.
  
  Regards,
  
  Soumya
- October 8, 2018 at 6:18 am
  
  Keyur Kanade
  Ansys Employee
  
  Hi,
  
  You can use zero gauge pressure at the outlet. The flow is mainly driven by pressure gradient. When you use udf at inlet, the flow direction will depend on pressure at inlet.
  
  Hope this helps.
  
  Regards,
  
  Keyur
- October 8, 2018 at 6:19 am
  
  Keyur Kanade
  Ansys Employee
  
  You may want to look at this post
  
  https://forum.ansys.com/forums/topic/need-answer-of-very-basic-questions-what-is-back-flow-in-fluent-simulation/
  
  Regards,
  
  Keyur

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