reverse flow occur while activating open channel flow boundary?

mariam.sara · April 11, 2015, 16:34

Hello I have a real problem with open channel flow reverse flow still occur while using open channel flow boundary i tried transient and I patch the water region volume fraction with 1 but how i overcome reverse flow problem I really need help with it?

CeesH · April 15, 2015, 07:07

Hi, why is backflow an issue? can it not just be a physical phenomenon in this case?

mariam.sara · April 15, 2015, 07:23

Hi you mean backflow will not effect the results? currently the velocity results not acceptable with that obtained from literature?

CeesH · April 15, 2015, 07:35

backflow may or may not be a physical phenomenon. it certainly isn't an error. It could be physical, if for example the outlet is located in a re-circulation zone after some obstacle. Or it may not be, as it seems to be in your case if the velocity results are not in line with literature. But in that case, backflow is a symptom, not the cause I'd say. It could be mesh refinement helps, or maybe the turbulence model you are using (if any) is not applicable for the current simulation. Can you provide some images of the results maybe, so we can see where the problems occur?
Best,
Cees

mariam.sara · April 21, 2015, 15:15

Hello sorry if i late with respond because I am busy with exams. I have a simple geometry 2D channel and no turbulence model is used its laminar flow. My problem in brief I have stratified two phase Air-Water flow the air in top and water in bottom i used currently open channel flow boundary to find velocity distribution on both phases. I do not understand what kind of images you ask me to post?

CeesH · April 25, 2015, 11:27

mesh and velocity vectors would help I think

mariam.sara · April 25, 2015, 14:30

I do not think there is any problem with mesh I check skweness factor its nearly 0.013 and aspect ratio is good too nearly 1.4?

CeesH · April 26, 2015, 07:24

Nope, but I don't really care about the mesh quality. I want to see what the domain looks like to judge if the backflow is physical or artificial

April 11, 2015, 16:34	reverse flow occur while activating open channel flow boundary?	#1
mariam.sara Senior Member Join Date: Jan 2011 Posts: 339 Rep Power: 16	Hello I have a real problem with open channel flow reverse flow still occur while using open channel flow boundary i tried transient and I patch the water region volume fraction with 1 but how i overcome reverse flow problem I really need help with it?

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April 15, 2015, 07:07		#2
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	Hi, why is backflow an issue? can it not just be a physical phenomenon in this case?

April 15, 2015, 07:23		#3
mariam.sara Senior Member Join Date: Jan 2011 Posts: 339 Rep Power: 16	Hi you mean backflow will not effect the results? currently the velocity results not acceptable with that obtained from literature?

April 15, 2015, 07:35		#4
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	backflow may or may not be a physical phenomenon. it certainly isn't an error. It could be physical, if for example the outlet is located in a re-circulation zone after some obstacle. Or it may not be, as it seems to be in your case if the velocity results are not in line with literature. But in that case, backflow is a symptom, not the cause I'd say. It could be mesh refinement helps, or maybe the turbulence model you are using (if any) is not applicable for the current simulation. Can you provide some images of the results maybe, so we can see where the problems occur? Best, Cees

April 21, 2015, 15:15		#5
mariam.sara Senior Member Join Date: Jan 2011 Posts: 339 Rep Power: 16	Hello sorry if i late with respond because I am busy with exams. I have a simple geometry 2D channel and no turbulence model is used its laminar flow. My problem in brief I have stratified two phase Air-Water flow the air in top and water in bottom i used currently open channel flow boundary to find velocity distribution on both phases. I do not understand what kind of images you ask me to post?

April 25, 2015, 11:27		#6
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	mesh and velocity vectors would help I think

April 25, 2015, 14:30		#7
mariam.sara Senior Member Join Date: Jan 2011 Posts: 339 Rep Power: 16	I do not think there is any problem with mesh I check skweness factor its nearly 0.013 and aspect ratio is good too nearly 1.4?

April 26, 2015, 07:24		#8
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	Nope, but I don't really care about the mesh quality. I want to see what the domain looks like to judge if the backflow is physical or artificial