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-   -   multiphase modelling (http://www.cfd-online.com/Forums/fluent/37832-multiphase-modelling.html)

Sumeet September 8, 2005 00:54

multiphase modelling
 
can anybody please guide me in multiphase modelling. i have to model water in square container heated and there is air above the surface . basically i have to generate the interface . pls suggest some model with the outline of procedure as well.

thank u, sumeet

zxaar September 8, 2005 01:39

Re: multiphase modelling
 
tutorials are best friends

Mary September 8, 2005 02:41

Re: multiphase modelling
 
VOLUME OF FLUID is the model you should use. You have to define two phases: air (primary phase) and water In Operating conditions of course you have to include gravity, operating pressure is 101325 Pa (if container is opened to atmosphere) and don't forget to specify reference pressure location

I hope it helps ...

srik September 8, 2005 05:15

Re: multiphase modelling
 
Hi, I am also trying similar type of problem. An rectangular open channel with water and air. I could not find any fluent tutorials related to open channel flow. Can anyone suggest right BC for open channel flow and any sample cases run on fluent....

Thanks in advance


Mary September 8, 2005 06:05

Re: multiphase modelling
 
OPEN CHANELL FLOW. One BC is above air - define it as pressure-inlet, name:OPEN And of course another two BC are velocity inlet (name-INLET) and pressure outlet (name-OUTLET)(defined as the whole area of chanell) and wall of the chanell of course. FLUENT: Multiphase model - Volume of fluid Number of phases: 2 (air and liquid water) Define materials- add water liquid Define Phases- Phase 1 (AIR) and Phase (2) (water-liquid) Define operating conditions- include gravity check Specified operating density Operating pressure 101325 and reference pressure location -give exactly the coordiantes of one point on the BC (OPEN) Be carefull when you initialize. After that you sholud patch, d.h. Adapt-Region (in order to make register where the air is-you have 3 shapes), this is important - hier you mark the region where is air. And then Solve-Initialize-Patch (now you have your register) select the register, write the volume fraction of phase 2 (water-liquid) it is 0 (now you defined where is the air)and click Patch. And then try to iterate ... etc.


srik September 9, 2005 01:30

Re: multiphase modelling
 
Hi, Thank you very much for the suggestions. I am able to simulate open channel with VOF Method using the above conditions. But I am unable to simulate the same problem using "open channel" option in VOF method. I am using mass-flow-inlet condition in which only free surface level need to be specified, pressure outlet condition in which free-surface level has to be specified and top boundary which, I am specifying as symmetry, since specifying top as pressure inlet is causing divergence. I am patching the water phase using adapt-region and initialize-patch. The problem I am facing is the water level in the domain is increasing above the free-surface level specified.

Thanks in advance

Rashmi September 26, 2005 02:34

3d cylinder
 
hello everyone

plz let me knw if anyone knows how to create 3d cylindrical pipe with structured meshing..i want to transform the cylinder to mappable...plz explain

thanx in advance

Ehab October 9, 2005 15:06

Re: 3d cylinder
 
Hi Rashmi, Did you find out how to solve this problem. I have the same one, I'm simulating a liquid flow from a circular tank via a horizontal narrow and short pipe to the atmosphere. I'm trying to capture the liquid surface using VOF (unsteady formulation). I'm having difficulty and have been told the mesh should be structured while I'm using unstructured one.

So, please, if you have know how, let me know.

Thanks.

rashmi October 11, 2005 01:40

Re: 3d cylinder
 
hi sorry for delay as i was not well.......... if u want to create structured meshing then u shud do it by virtual edge split and face split operations....

first create a 3d cylinder and split the edges of the cylinder with point equally with edges virtual connected and then split the face (ie the whole face).then u can mesh the cylinder by map scheme.then mash the whole volume my cooper..the vol created will be virtual so after meshing u can transform the volume into real.

hope this will help u good luck rashmi

makkks July 4, 2011 00:07

Hi guys,

similar problem but with oil and air.
closed fin with oil running thru and air blowing on top.
I have defined two diff domains in CFX-pre: AIR and OIL.
In basic settings where we have to define Fluid and particle definitions , I have added oil and Air .
The problem I am facing is to define "Buoyant Reference Density"...
I am not able to separately define thr densities...Its only taking 1 density at a tym.
Ref den of air- 1.185
Ref den of oil - 830.33
as soon as i put 1.185 for air , oil density turns into 1.185.

Thanks for help :)

Muhammed_iraq December 12, 2014 07:33

adapt region
 
Hi all

Please i want to adapt region for 3D clylinder
, it has diameter 20mm and length 700 mm

what the value of Xmin,Ymin,Zmin and Xmax,Ymax,Zmax and the radius?????when i will go to menu adapt>>region

Many Thanks

Muhammed_iraq December 12, 2014 07:35

adapt region
 
Hi Mary

Please i want to adapt region for 3D clylinder
, it has diameter 20mm and length 700 mm

what the value of Xmin,Ymin,Zmin and Xmax,Ymax,Zmax and the radius?????when i will go to menu adapt>>region

Many Thanks



Quote:

Originally Posted by Mary
;124045
OPEN CHANELL FLOW. One BC is above air - define it as pressure-inlet, name:OPEN And of course another two BC are velocity inlet (name-INLET) and pressure outlet (name-OUTLET)(defined as the whole area of chanell) and wall of the chanell of course. FLUENT: Multiphase model - Volume of fluid Number of phases: 2 (air and liquid water) Define materials- add water liquid Define Phases- Phase 1 (AIR) and Phase (2) (water-liquid) Define operating conditions- include gravity check Specified operating density Operating pressure 101325 and reference pressure location -give exactly the coordiantes of one point on the BC (OPEN) Be carefull when you initialize. After that you sholud patch, d.h. Adapt-Region (in order to make register where the air is-you have 3 shapes), this is important - hier you mark the region where is air. And then Solve-Initialize-Patch (now you have your register) select the register, write the volume fraction of phase 2 (water-liquid) it is 0 (now you defined where is the air)and click Patch. And then try to iterate ... etc.



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