[saiburry]

hey,guys.

i have facing a problem.now i am modeling the two phase flow in a horizontal pipe for practice, like the stratified flow,the wavy flow and the annular flow...etc.

But , does anyone have the Tutorial about the two phase flow in the horizontal pipe ?

I have been reference the flow regime map by Baker to set my BC's, and I used the VOF model. But I want to check my another setting.

Can anybody help me?

[kbaker]

No available tutorial about horizontal two phase flow you need to set two inlets or single inlet for the individual phases. for one inlet you need to set the vof of the secondary phase and the mixture velocity and for 2 inlets you need to set the velocity for each phase separately with setting vof for secondary phase as 1 and zero hope this can help u.

k.baker

[saiburry]

thanks u a lot!
now i am using the geometry which have two inlet, but i want to try the case with one inlet.
Can u explain the mixture velocity more?

[kbaker]

The mixture velocity can be defined as the sum of the superficial velocities of the individual phases you can define only one inlet with giving the value of mixture velocity then you need to define the value of vof for secondary phase at inlet this must be known if you solving your problem for stratified flows it depend on the level of the liquid at the bottom of the pipe you can refer for any multiphase flow book for more details about it.

[saiburry]

so, if the superficial liquid velocity is 5 m/s, and the superficial gas velocity is 3 m/s, the mixture velocity of my case is 8 m/s and i need to define the volume fraction of the secondary phase at velocity inlet condition, right?

but, which phase i should set to be the secondary phase?
in stratified flow and slug flow, i set the gas as the secondary phase. does it wrong?

[kbaker]

In case of stratified flow the liquid phase must be selected as secondary phase cause it be on the bottom of the pipe but the operating density must be selected for the gas phase in case of slug flow I am not sure about it you need to ask other colleagues.

[saiburry]

ok, i got it! thank u a lot!

so,the mixture velocity which i mention about in last post is right?

[kbaker]

Yes you right

[saiburry]

about the volume fraction of the secondary phase, in stratified flow, you say that the volume fraction depend on the thickness of the secondary flow, but how can i know the thickness before the simulate finished?

[kbaker]

If you tried single inlet you need just to define the vof of secondary flows but this unuseful if you solved for unsteady flow because at the last time step you will never see the liquid level hence if you want unsteady solution its better for you go to two inlets case and in this case you need to draw the heights of each inlets in Gambit this is necessary to fluent to set an initial distribution of phases you need to let the case run until the phases full the pipe so you may need some time long.

[ahmedsh974]

you can explain two inlet in details

[maryam74121]

hi
i am simulating a model with two vents and one outlet.the water patched into the main chamber and air can goes in and out from two vents. i want to simulating water flow in channel.
i dont have any parameters in vents what is the best boundary condition for them? the vents are in the atmosphere pressure but the whole model is rotating so i dont know the gauge pressure=0 in correct for these vents or not?
i use the out flow for outlet which it is incompatible with pressure boundaries.
i cant see the right flow in channel is there any one could help me?
the residuals cant decrease enough and continuity residuals are in order of 10
i appreciate your recommendations