# vof_boundary

 Register Blogs Members List Search Today's Posts Mark Forums Read

 September 21, 2007, 05:34 vof_boundary #1 garima chaudhary Guest   Posts: n/a hi all, i am using VOF model for centrifugal contactor to simulate inner rotor zone. have a query regarding the backflow volume fraction ,since in VOF model it will ask only the volume fraction for secondary phase but not for primary phase . so i want to know if i specify backflow volume fraction for water as zero at the top what value does it take for air the primary phase. i would like to clarify that in pressure outlet condition i need to specify the volume fraction of the secondary phase which is water in my case and air is the primary phase. So ideally speaking, at the top of the cylinder water should be thrown out, hence i specified zero backflow volume fraction of the water over there,but as i have seen it doesnt ask to specify the backflow volume fraction for air, so my query is what volume fraction value will it take for air at that boundary because i dont want even air to be flowing in or out at that boundary only water should be thrown out there. plz help me regarding this issue Regards garima

 September 24, 2007, 17:33 Re: vof_boundary #2 Vimal Guest   Posts: n/a Hi Garima, (1) You might want to specify "water" as the primary-phase and "air" as the secondary phase. (2) In the case of the pressure outlet condition, if you specify the back-flow fraction for one of the phases to be ZERO, the other is automatically taken as ONE. Hope this helps. Vimal

 September 25, 2007, 02:01 Re: vof_boundary #3 garima chaudhary Guest   Posts: n/a hi thanx for ur guidance ok if the backflow volume fraction for the phase which is not being asked is taken as 1-(the volume fraction specified for other phase), then can u plz tell what boundary condition shud i take if i want the following situation to model: my system consists of a rotating cylinder(i.e. rotor of the centrifugal contactor) in which i m employiong the use of VOF model to simulate fluid flow in it. the cylinder has an inlet at the bottom thru which water enters and it goes out thru the top annular ring. this annular ring at the top is defined as pressure outlet b.c. , also there is a small opening at the centre of the top which lets the water rotating in cylinder exposed to atmosphere. so there are 2 fluids air and water. now at the top where i hav specified pressure outlet b.c. i need only water to leave out and no backflow of it and also no air shud come in or going out thru that opening then how shud i employ that . plz guide thanks garima

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

All times are GMT -4. The time now is 20:11.