# Question about VOF method

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 January 15, 2016, 00:42 Question about VOF method #1 Member   Zhifang Hu Join Date: Sep 2015 Location: Brisbane Posts: 53 Rep Power: 3 I did a two-phase flow simulation using VOF method, with alpha defining as 1 for water and 0 for air. After the simulation, i tried to do some analysis on water level using sampling along a cross section. The results show there are sampling points with alpha value between 0 and 1, like 0.7 sth. I am wondering if there is any standard to determine if the point is considered to be air or water based on the alpha value or other factors. For instance, i may say the point is considered to be water if alpha is bigger than 0.5 at that point, or sth else. Anyone have any suggestion? Thanks in advance.

 January 15, 2016, 04:00 #2 Senior Member   Hesam Join Date: Feb 2015 Posts: 139 Rep Power: 3 Hi Zhifang Hu, In VOF method any value between 0 and 1 show the interface. base on VOF,volume fraction (alpha) is : volume of liquid that occupy the cell/total volume of cell,therefore,you can argue that when alpha is 0.7,70% of cell occupied by liquid and 30% occupied by gas.therefore,in alpha=0.7 you have mixture of gas and liquid that has more contribution of liquid.

January 17, 2016, 19:15
#3
Member

Zhifang Hu
Join Date: Sep 2015
Location: Brisbane
Posts: 53
Rep Power: 3
Quote:
 Originally Posted by rapierrz Hi Zhifang Hu, In VOF method any value between 0 and 1 show the interface. base on VOF,volume fraction (alpha) is : volume of liquid that occupy the cell/total volume of cell,therefore,you can argue that when alpha is 0.7,70% of cell occupied by liquid and 30% occupied by gas.therefore,in alpha=0.7 you have mixture of gas and liquid that has more contribution of liquid.
Hi there.

Thanks for the reply.

I do understand the volume fraction alpha, but what i am thinking is that if there is some kinds standard threshold value for alpha to define the point if it can be considered as water or air.

For instance, i can define alpha smaller than 0.5, the point to be air, else is water. or I calculate the point that which the mass of water is more than half to be water cell, or may be alpha is zero for air, else for water. etc

I did some research on it, but nvr find one till now, thats why i am wondering if this kind of threshold exist in defining a point to be water or air.

 January 18, 2016, 03:24 #4 Senior Member     Anton Kidess Join Date: May 2009 Location: Delft, Netherlands Posts: 1,163 Rep Power: 20 If you want to do it properly, you will need some sort of geometric reconstruction such as PLIC. __________________ *On twitter @akidTwit *Spend as much time formulating your questions as you expect people to spend on their answer. *Join the OpenFOAM stackexchange Q&A site: http://area51.stackexchange.com/prop...oHPxcPqde7HtA2

 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

 Similar Threads Thread Thread Starter Forum Replies Last Post Greg Perkins Main CFD Forum 2 September 10, 2012 04:05 yeeking86 CFX 7 August 23, 2010 18:24 CFDtoy Main CFD Forum 3 September 24, 2006 13:40 Thomas Main CFD Forum 3 August 9, 2006 12:37 tommewang Main CFD Forum 1 May 19, 2003 08:10

All times are GMT -4. The time now is 16:57.

 Contact Us - CFD Online - Top