# Who understand Bump Tutorial?

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 May 18, 2012, 12:36 Who understand Bump Tutorial? #1 Senior Member   Join Date: Jan 2011 Posts: 235 Rep Power: 8 I need to know is UpH in bump tutorial represents the free surface height at inlet while DownH is the free surface level at outlet? I am really confused about it may somebody answer me please?

 May 19, 2012, 01:11 Hi #2 Senior Member   Danial Join Date: Nov 2011 Posts: 179 Rep Power: 6 Yes, that is what tutorial states. UpH is for inlet and DownH is for outlet.

 May 20, 2012, 10:44 #3 Senior Member   Join Date: Jan 2011 Posts: 235 Rep Power: 8 Thanks Danial for the answer. In my case the lower phase is flows with a velocity differ from the upper phase velocity. In bump tutorial they only use single velocity at inlet I want to set the two velocities at inlet together for both phases. As I know from the guys on the forum this is possible unless the two phases never mixed and I can still use homogeneous model . Someone said that If the free surface is at z=10 mm, then for z<10 mm I need to define velocity=0.5 [m/s], and where z>10 mm I need define velocity=1[m/s]? I aware that I need use a CEL expression for it but I am a beginner with CFX may you please type how the CEL expression for this case become? Knowing that I read the examples mentioned about CEL expression at the documentation but never find similar one to my case? Thanks a lot Mariam Last edited by mariam.sara; May 20, 2012 at 11:00.

 May 20, 2012, 17:34 HI #4 Senior Member   Danial Join Date: Nov 2011 Posts: 179 Rep Power: 6 it would be like this;if you have one for inlet and for both velocities : if(z>=10[m/s],if(z<=0.5[m/s],1[m/s],0.5[m/s],0[m/s]) it should work, i think so. try it and if it does not ,post it here and you can get suggestions from anyone.

May 21, 2012, 01:49
#5
Senior Member

Join Date: Jan 2011
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Rep Power: 8
HI Danial I not understood something in your last expression? From where you bring 0 [m/s] velocity? I never set like this velocity at my last post? furthermore I think there is error in your expression it must be as follows as I think:
if(z>=10 mm,if(z<=10 mm,1[m/s],0.5[m/s])

is it right?

another thing how can I define this expression in my simulations for the velocity at inlet? in Bump tutorial they give each expression a known symbol (like UpH,DownPre,.......etc) should I give symbol for this expression too?

Quote:
 Originally Posted by Danial Q it would be like this;if you have one for inlet and for both velocities : if(z>=10[m/s],if(z<=0.5[m/s],1[m/s],0.5[m/s],0[m/s]) it should work, i think so. try it and if it does not ,post it here and you can get suggestions from anyone.

 May 21, 2012, 23:59 HI #6 Senior Member   Danial Join Date: Nov 2011 Posts: 179 Rep Power: 6 yes , u will hv to give name like " V "for velocity while creating expressions, earlier expressions must have an error because, units will be written such as; [m s^-1] rather [m/s]. Zero velocity means if your fluids have velocities as u defined, they will take the value of your velocity proposed (1 or 0.5]. Otherwise, if they dont fall in those ranges, velocity will be considered zero. Insert > expressions > [name wteva u like] if(z>=10[mm],if(z<=0.5[mm],1[m s^-1],0.5[m s^-1]),0[m s^-1])

 May 22, 2012, 10:31 #7 Senior Member   Join Date: Jan 2011 Posts: 235 Rep Power: 8 Depending on the expression you mentioned I type the following statement: if(y>0.01 [m],if(y<=0.01 [m],12.5 [m s^-1],0.0066 [m s^-1]),0 [m s^-1]) where y vertical distance 0.01 m is the free surface level when I try test the expression before run in cfx-pre it gives zero velocity everywhere along y so what the problem? may somebody tell me? is the expression incorrect? Last edited by mariam.sara; May 22, 2012 at 11:13.

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