[zainab]

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]

[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

[zainab]

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.

[kbaker]

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

[Kanarya]

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!!!

[kbaker]

Vague question lead to vague answer give some details about what you want to do.

[Kanarya]

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!!!

[Kanarya]

Hi
is there anybody to help me?

thanks in advance!!

[Yanlong Li]

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.

[Kanarya]

Originally Posted by Yanlong Li

Hi man,

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

hi,

yes,please...
whrere is the mistake?

I can not find it..

thanks for the answer!

[Yanlong Li]

if (C_UDMI(c0,t0,2) =0)

this line:
if (C_UDMI(c0,t0,2) ==0)

[Kanarya]

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

[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.

[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

[Kanarya]

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?

[Kanarya]

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

[Kanarya]

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)

}

[msaeedsadeghi]

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*/
Thread *ct;
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*/
}

[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

[Kanarya]

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!