outlet conditions

h-banana · August 27, 2012, 05:34

hey im new to CFX and am just starting a project at a new company where i am looking at two phase flow, water particles in air through a vane/vent type enclosure.
i am having problems with my outlet conditions, is it possible to not have to input and conditions here, I have tried just setting the static pressure but this puts up a wall which restricts flow, setting a velocity changes the flow through the vent.. I also tried using an opening as opposed to an outlet but it crashed every time. Not sure If theres probably a very simple solution to this problem.??

bratzinger · August 27, 2012, 07:39

Hi

i would enlarge the outflow region and evaluate the plane where your former outlet region was or evaluate a bit downstream

otherwise the results could be compromised because the outlet condition forces the eddy to end upstream(noticed that in an OpenFOAM-case with outlet-condition) or you could have problems with convergence(my experience with a heatflow analysis in an Ansys-case where i tried to set the inflow-temperature of the opening-condition with an massFlowAve(T)@outlet-expression) and maybe the missing convergence causes the solver to crash in your case

ghorrocks · August 27, 2012, 07:55

Can you post an image of what you are modelling and the flow applied to it?

h-banana · August 27, 2012, 21:03

this is the mesh, I need to model the water particles track where they become trapped in the grooves of the vent.

ghorrocks · August 28, 2012, 07:23

If the flow is high Re then your exit boundary is too close. You need to move it downstream - bratzinger's comment is correct.

August 27, 2012, 05:34	outlet conditions	#1
h-banana New Member henry Join Date: Aug 2012 Posts: 2 Rep Power: 0	hey im new to CFX and am just starting a project at a new company where i am looking at two phase flow, water particles in air through a vane/vent type enclosure. i am having problems with my outlet conditions, is it possible to not have to input and conditions here, I have tried just setting the static pressure but this puts up a wall which restricts flow, setting a velocity changes the flow through the vent.. I also tried using an opening as opposed to an outlet but it crashed every time. Not sure If theres probably a very simple solution to this problem.??

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August 27, 2012, 07:39		#2
bratzinger New Member Join Date: Jul 2012 Location: Germany Posts: 23 Rep Power: 13	Hi i would enlarge the outflow region and evaluate the plane where your former outlet region was or evaluate a bit downstream otherwise the results could be compromised because the outlet condition forces the eddy to end upstream(noticed that in an OpenFOAM-case with outlet-condition) or you could have problems with convergence(my experience with a heatflow analysis in an Ansys-case where i tried to set the inflow-temperature of the opening-condition with an massFlowAve(T)@outlet-expression) and maybe the missing convergence causes the solver to crash in your case

August 27, 2012, 07:55		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Can you post an image of what you are modelling and the flow applied to it?

August 28, 2012, 07:23		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	If the flow is high Re then your exit boundary is too close. You need to move it downstream - bratzinger's comment is correct.