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-   -   Who understand Bump Tutorial? (http://www.cfd-online.com/Forums/cfx/101982-who-understand-bump-tutorial.html)

 mariam.sara May 18, 2012 12:36

Who understand Bump Tutorial?

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?

 Danial Q May 19, 2012 01:11

Hi

Yes, that is what tutorial states. UpH is for inlet and DownH is for outlet.

 mariam.sara May 20, 2012 10:44

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

 Danial Q May 20, 2012 17:34

HI

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.

 mariam.sara May 21, 2012 01:49

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 (Post 362074) 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.

 Danial Q May 21, 2012 23:59

HI

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])

 mariam.sara May 22, 2012 10:31

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?

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