# gas-liquid slug flow in horizontal pipe

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 March 30, 2012, 15:09 gas-liquid slug flow in horizontal pipe #1 New Member   zainab Join Date: Mar 2012 Posts: 17 Rep Power: 10 Hello every one, I am a new member. I working on Fluent for modeling a two-phase, gas-liquid (air-water) slug flow in a pipe and I need some help please. My case: pipe length (583cm), (1.27cm) diameter, drawing and meshing by Gambit, the total elements was (112896 cell(, the pipe inlet set to (velocity-inlet), outlet to (outflow), pipe surface to (wall), the pipe continuum to (fluid). In fluent the define sequence as: 1. Solver: pressure based, unsteady, implicit scheme. 2. Multiphase: VOF. 3. Viscous: k-epsilon, standard. 4. Phases: primary as water, secondary as air, interaction: wall adhesion, surface tension (0.07). 5. Operating condition: gravity at y (-9.81), specified operating density. 6. Boundary condition: a. mixture velocity (1.6), k(0.025), epsilon(0.0072). b. air – multiphase volume fraction (1). 7. Initialize: vf=0.18, patch: air vf =0.18. I have a problem I need to get the contour of the slug vf, volume fraction? And, do I need to use a UDF for the velocity?[/FONT] modheji likes this.

 April 2, 2012, 01:35 gas-liquid slug flow in horizontal pipe #2 Senior Member   Vaze Join Date: Jun 2009 Posts: 171 Rep Power: 13 Hi For the dimensions specified by you, track the flow regime map and then suitable specify the velocity of the gas and water at the inlet. Patching of the secondary phase will increase the speed of the solver towards the solution, otherwise without patching run it from scratch (water filled initially) and define the velocity as a function of time; will give you various flow patterns. Regards mvee

July 27, 2012, 14:55
#3
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zainab
Join Date: Mar 2012
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Quote:
 Originally Posted by mvee Hi For the dimensions specified by you, track the flow regime map and then suitable specify the velocity of the gas and water at the inlet. Patching of the secondary phase will increase the speed of the solver towards the solution, otherwise without patching run it from scratch (water filled initially) and define the velocity as a function of time; will give you various flow patterns. Regards mvee
Hi mvee do you mean that i must use a user defined function for the velocity profile.

 August 11, 2012, 17:31 #4 Senior Member     Khalid Baker Join Date: Mar 2009 Location: IRAQ Posts: 168 Rep Power: 13 Slug can obtained from stratified flow but the point of transporting stratified to slug depend on the phase velocities (especially higher gas velocity give slug flow) hence if you get stratified flow successfully just increase the gas velocity then with progress of the run with time you will get it? furthermore you need to check the range of your phase velocities that fulfill slug flow refer to any flow regime map to check it and I prefer that given by Taitel & Duckler Flow regimes map for horizontal pipes. kbaker modheji and hellaadouni like this.

 January 16, 2013, 07:43 to use outlet velocity in inlet #5 Senior Member   Join Date: May 2011 Posts: 231 Rep Power: 12 hi, is ti possible to use this command in inlet where C_UDMI(c,t,2) is outlet velocity F_PROFILE(c,t,i) = C_UDMI(c,t,2); thanks in advance!!! modheji likes this.

 January 16, 2013, 07:56 #6 Senior Member     Khalid Baker Join Date: Mar 2009 Location: IRAQ Posts: 168 Rep Power: 13 Vague question lead to vague answer give some details about what you want to do. hellaadouni likes this.

 January 16, 2013, 08:05 #7 Senior Member   Join Date: May 2011 Posts: 231 Rep Power: 12 thanks for quick answer! I am simulating gas-solid flow. So I want to save velocity and volume fraction in outlet and then to use it in inlet so I managed to save it with C_UDMI but in inlet everything is zero it seems it doesnt work. here is my inlet profile: DEFINE_PROFILE(abs_vel,t,i) { Domain *d; cell_t c, c0; face_t f; Thread *ct,*t0; begin_f_loop(f,t) { c0 = F_C0(f, t); t0 = THREAD_T0(t); if (C_UDMI(c0,t0,2) =0) F_PROFILE(f,t,i)=0.001; else F_PROFILE(f,t,i) = C_UDMI(c0,t0,2); } end_f_loop(f,t) } thanks for your help!!!

 January 18, 2013, 05:16 help for inlet profile #8 Senior Member   Join Date: May 2011 Posts: 231 Rep Power: 12 Hi is there anybody to help me? thanks in advance!!

January 18, 2013, 07:06
#9
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Yanlong Li
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Quote:
 Originally Posted by Kanarya thanks for quick answer! if (C_UDMI(c0,t0,2) =0) thanks for your help!!!
Hi man,

You made a mistake, do I need to correct it.

January 18, 2013, 07:13
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Quote:
 Originally Posted by Yanlong Li Hi man, You made a mistake, do I need to correct it.
hi,

whrere is the mistake?

I can not find it..

 January 18, 2013, 09:01 #11 Member   Yanlong Li Join Date: Jan 2013 Location: BeiJing Posts: 47 Rep Power: 9 if (C_UDMI(c0,t0,2) =0) this line: if (C_UDMI(c0,t0,2) ==0)

January 18, 2013, 09:07
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Quote:
 Originally Posted by Yanlong Li if (C_UDMI(c0,t0,2) =0) this line: if (C_UDMI(c0,t0,2) ==0)
thanks Yanlong!

I did but it still doesnt work. it seems C_UDMI doesnt work for profile...
I dont know why?

Thanks again

 January 18, 2013, 21:52 #13 Member   Yanlong Li Join Date: Jan 2013 Location: BeiJing Posts: 47 Rep Power: 9 Hi, There was another mistake, the value you stored was the UDM of outlet, but what you used was the UDM of inlet, so you never change (or store) the value into inlet. I have an idea, when you calculate the value of the outlet, you should get the thread (such as *tt) of inlet, if (((X_out - X_in)^2 + (Y_out - Y_in)^2) < 10^(-4)) F_UDMI(ff,tt,i) = value. hope it can help.

 January 19, 2013, 00:21 #14 Senior Member   Vaze Join Date: Jun 2009 Posts: 171 Rep Power: 13 Hi Kanarya Another way you can follow is: (1) save the velocity profile in memory location (2) using DEFINE_ADJUST, employ this velocity profile on inlet Best wishes Mvee

January 19, 2013, 18:23
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Quote:
 Originally Posted by mvee Hi Kanarya Another way you can follow is: (1) save the velocity profile in memory location (2) using DEFINE_ADJUST, employ this velocity profile on inlet Best wishes Mvee
thanks a lot!

with DEFINE_ADJUST,it seems working now but it gives inlet very small values comparison to outlet like(solid phase mass flow rate in inlet 1.3,outlet 227) but I don't understand why?
do you have any idea?

January 19, 2013, 18:26
#16
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Quote:
 Originally Posted by Yanlong Li Hi, There was another mistake, the value you stored was the UDM of outlet, but what you used was the UDM of inlet, so you never change (or store) the value into inlet. I have an idea, when you calculate the value of the outlet, you should get the thread (such as *tt) of inlet, if (((X_out - X_in)^2 + (Y_out - Y_in)^2) < 10^(-4)) F_UDMI(ff,tt,i) = value. hope it can help.
hi Yanlong Li,

thanks a lot for your help!
I think it should work without value as well..

best!thanks again

January 19, 2013, 18:29
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Quote:
 Originally Posted by mvee Hi Kanarya Another way you can follow is: (1) save the velocity profile in memory location (2) using DEFINE_ADJUST, employ this velocity profile on inlet Best wishes Mvee
this is my inlet profile:
DEFINE_PROFILE(solid_massflow, t, i)
{ cell_t c; face_t f; Thread *ct;
begin_c_loop(c, t)
{ ct = t->t0;
F_PROFILE(c,t,i) = C_UDMI(c,ct,0);}
end_c_loop(c,t)

}

January 20, 2013, 01:09
#18
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SSL
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Quote:
 Originally Posted by Kanarya this is my inlet profile: DEFINE_PROFILE(solid_massflow, t, i) { cell_t c; face_t f; Thread *ct; begin_c_loop(c, t) { ct = t->t0; F_PROFILE(c,t,i) = C_UDMI(c,ct,0);} end_c_loop(c,t) }
In PROFILE UDFs you should use face not cells. Correct this UDF.

DEFINE_PROFILE(solid_massflow, t, i)
{
cell_t c;
face_t f; /* this format should not be changed*/
begin_f_loop(f, t) /* this format should not be changed*/
{
ct = t->t0;
F_PROFILE(f,t,i) = ..... ;/* this format should not be changed*/
}
end_f_loop(f,t) /* this format should not be changed*/
}

 January 21, 2013, 00:14 #19 Senior Member   Vaze Join Date: Jun 2009 Posts: 171 Rep Power: 13 Hi Kanarya Please check by putting the monitor point that your inlet and exit velocities are similar or not? This is to ensure that your inlet velocities are updating at each iterations. Best wishes Mvee

January 21, 2013, 05:11
#20
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Quote:
 Originally Posted by mvee Hi Kanarya Please check by putting the monitor point that your inlet and exit velocities are similar or not? This is to ensure that your inlet velocities are updating at each iterations. Best wishes Mvee
Hi Mvee,

yes they are updating but they are different(much smaller) than outlet.
I do know why?

thanks again!

Best!

 Tags gas-liquid, horizontal pipe, slug, two-phase, volume fraction