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Reversed flow in XXX faces on pressure outlet |
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#1 |
New Member
asdasdasd
Join Date: Aug 2012
Posts: 15
Rep Power: 14 ![]() |
Hi,
I'm trying to model two static mixers in a serial configuration with helical elements. The length of the geometric model is around 72 inches from the inlet to the outlet with helicals running the first 34 inches with a 3 inch break then another 34 inches of helicals. I have my axis's set so that the Z is the direction of the fluid flow. I then put a magnitude of 0.00025 m/s in the direction normal to the boundary (i'm assuming this is going to give me flow along the Z axis and when I look at my contours it does). The inlet is set as a velocity boundary condition (where I inputted the magnitude of the flow) and the outlet as a pressure outlet condition that I left as default. I'm using a non-newtonian fluid in the flow domain as well. I also am initializing my solution via the standard method. When I run my simulation I get the error as in the title. Is this something that I need to be worried about or can I just leave it as it is? How do I get rid of this as well. |
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#2 |
Senior Member
Philipp
Join Date: Jun 2011
Location: Germany
Posts: 1,297
Rep Power: 27 ![]() |
Hi,
Reversed flow means, your flow comes from the pressure outlet into your domain instead of going out through it. Sometimes it happens, when your initial guess is bad... or if strong vorticies (with backflow) go out through the outlet. Does the message vanish after some iterations? Are you running a time dependent simulation? Did you try to use a different initialization? |
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#3 |
New Member
asdasdasd
Join Date: Aug 2012
Posts: 15
Rep Power: 14 ![]() |
The message does not go away so far however I'm going to run a lot more iterations and see if it does. The number decreases then increases again.
I'm also going to try initializing the solution with a different velocity and pressure to see if that changes anything. Besides this anything else that I should do? |
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#4 |
Senior Member
Philipp
Join Date: Jun 2011
Location: Germany
Posts: 1,297
Rep Power: 27 ![]() |
Again: Are you running a time dependent simulation?
If your steady state solution seems to "swing" it could be a hint, that your problem is actually time dependent and the solver has problems to "force it" to a steady solution. |
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#5 |
Super Moderator
Alex
Join Date: Jun 2012
Location: Germany
Posts: 3,426
Rep Power: 49 ![]() ![]() |
The FAQ for Ansys CFX covers the same situation in Fluent:
http://www.cfd-online.com/Wiki/Ansys...f_an_OUTLET.22 |
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#6 |
New Member
Nik
Join Date: Mar 2010
Location: Michigan
Posts: 25
Rep Power: 16 ![]() |
Try to extend the outlet and see if that helps to get rid of the reverse flow
The message does not mean something is wrong. It just gives you an indication of flow coming in and you may want to review your setup if that is something you are not expecting. |
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#7 |
New Member
Deldan Namgial
Join Date: Mar 2014
Posts: 5
Rep Power: 12 ![]() |
Sir
I working on earth air heat exchanger where air is pass through buried pipe underneath. while iteration i am also facing reverse flow at pressure outlet till end of iteration and solution does not converge. so what could causes of reverse flow since there is no reverse flow physically occurring in my study. |
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