# study the act of emtying of a tank(no inlet and an outlet)

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 May 11, 2009, 01:05 study the act of emtying of a tank(no inlet and an outlet) #1 Senior Member     hamed Join Date: Apr 2009 Posts: 148 Rep Power: 9 hi every one i want yo study the vortex made by emtying a tank or a pool whit a hole(outlet) in the bottom of it but how can i define the gradient of fluid at the surface of it i mean how can i see falling down(lowering ) the fluid surface ? thanks hamed

 May 11, 2009, 02:26 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,832 Rep Power: 100 Hi, The free surface will lower as the level goes down and probably form a low point a t the vortex. Is this what you mean? To see this is CFD-Post you draw an iso-surface of volume fraction = 0.5. Have a look at the flow over a bump tutorial problem to see how to set up a basic free surface flow simulation. Glenn Horrocks

 May 12, 2009, 23:51 how to define CEL #3 Senior Member     hamed Join Date: Apr 2009 Posts: 148 Rep Power: 9 thanks gelen for reply you got what axaclly i mean. i see that tutorial but i cant understand that CEL defined for example DownH 0.022 [m] ? and UpH =0.069 ? and this exprestion i brought downer. can you explain a little more what do i need? for that vortex problem and i should remind that the problem is transient but the tuterial was not and i didnt see eny volum fraction in water in that problem can you send me the CEL needed for the vortex problem whit dimention of a cylender whit 1 mheight filld up with water and the diameter of 0.5 m and a hol in the midel with 0.1m ? i will realy apratiat that UpVFAir step((y-UpH)/1[m]) UpPres DenH*g*UpVFWater*(UpH-y) DownVFAir step((y-DownH)/1[m]) DownVFWater 1-DownVFAir DownPres DenH*g*DownVFWater*(DownH-y)

 May 13, 2009, 18:43 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,832 Rep Power: 100 Hi, Sorry, I don't have time to set up demo problems for you. Ask CFX support for a demo problem or do a CFX training course. Otherwise do as many of the tutorials which come with CFX as you can so you can gain experience in using the software. Glenn Horrocks

 May 14, 2009, 00:28 #5 Senior Member     hamed Join Date: Apr 2009 Posts: 148 Rep Power: 9 tanks anyway

 May 14, 2009, 04:15 #6 Member     Rui Igreja Join Date: Mar 2009 Location: Aveiro Posts: 68 Blog Entries: 1 Rep Power: 9 From that tutorial (http://www.kxcad.net/ansys/ANSYS_CFX/help/help/Tutorials/i1315642.html): "These are expressions for the downstream free surface height, the density of the fluid, ..." DownH 0.022 [m] DenH 998 [kg m^-3] .... .... __________________ Rui

 November 3, 2009, 06:15 DownH= surface height below water free surface? #7 Member   mechovator Join Date: May 2009 Posts: 32 Rep Power: 9 Down stream means DownH= surface height below water free surface? and what UpH mean?

 November 3, 2009, 06:34 #8 Member     Rui Igreja Join Date: Mar 2009 Location: Aveiro Posts: 68 Blog Entries: 1 Rep Power: 9 http://www.kxcad.net/ansys/ANSYS_CFX.../i1315642.html "These are expressions for 1) the downstream free surface height, 2) the density of the fluid, 3) the upstream volume fractions of air 4) and water, 5) the upstream pressure distribution, 6) the downstream volume fractions of air 7) and water, and 8) the downstream pressure distribution." Name Definition 1) DownH: 0.022 [m] 2) DenH: 998 [kg m^-3] 3) UpVFAir: step((y-UpH)/1[m]) 4) UpVFWater: 1-UpVFAir 5) UpPres: DenH*g*UpVFWater*(UpH-y) 6) DownVFAir: step((y-DownH)/1[m]) 7) DownVFWater: 1-DownVFAir 8) DownPres: DenH*g*DownVFWater*(DownH-y) __________________ Rui

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