CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > FLOW-3D

water levelrise

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

Like Tree1Likes
  • 1 Post By jason_sjtu

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 5, 2013, 21:14
Default water levelrise
  #1
Member
 
bird
Join Date: Sep 2012
Posts: 42
Rep Power: 13
pyxbird is on a distinguished road
Dear all,
Hi, I am simulating flow in a flume, the inlet boundary is velocity boundary, however every time I begin the simulation, the water level will increase and extend to the outlet boundary and never descend. For example, the fluid elevation I define at the inlet and outlet boundary is 50cm, but after the flow becoming steady the water level keeps 55cm and never change. How can I solve this problem?
1.At the outlet boundary, I have tried continuative, pressure and outflow boundary.
2.I have tried to increase the velocity slowly at the inlet boundary but it doesn't work.
3.I have put an obstacle at the top of the flume to avoid water rising but the simulation will exit anormally.
So who can figure out why?
pyxbird is offline   Reply With Quote

Old   March 6, 2013, 01:01
Smile
  #2
New Member
 
PetiteHerbe
Join Date: Feb 2013
Posts: 3
Rep Power: 13
gdtiaozi is on a distinguished road
Model Setup->General->Interface tracking->Free surface or sharp interface

Model Setup->General->Number of fluids->One fluid

Model Setup->Meshing & Geometry->Initial->Void initial state->Pressure:101325Pa
gdtiaozi is offline   Reply With Quote

Old   March 6, 2013, 02:32
Default
  #3
Member
 
bird
Join Date: Sep 2012
Posts: 42
Rep Power: 13
pyxbird is on a distinguished road
Quote:
Originally Posted by gdtiaozi View Post
Model Setup->General->Interface tracking->Free surface or sharp interface

Model Setup->General->Number of fluids->One fluid

Model Setup->Meshing & Geometry->Initial->Void initial state->Pressure:101325Pa
Thank you, maybe I should give the pressure of air, I will try it soon.
pyxbird is offline   Reply With Quote

Old   March 6, 2013, 03:25
Default
  #4
Member
 
bird
Join Date: Sep 2012
Posts: 42
Rep Power: 13
pyxbird is on a distinguished road
Quote:
Originally Posted by gdtiaozi View Post
Model Setup->General->Interface tracking->Free surface or sharp interface

Model Setup->General->Number of fluids->One fluid

Model Setup->Meshing & Geometry->Initial->Void initial state->Pressure:101325Pa
It doesn't work, the level of the water still rises and doesn't dscend.
I will show two pitures below.
Attached Images
File Type: jpg fill fraction.jpg (71.5 KB, 67 views)
File Type: jpg fluid depth.jpg (35.1 KB, 85 views)
pyxbird is offline   Reply With Quote

Old   March 6, 2013, 04:35
Default
  #5
New Member
 
Jing
Join Date: Dec 2011
Posts: 20
Rep Power: 14
Jing_min is on a distinguished road
Quote:
Originally Posted by pyxbird View Post
Dear all,
Hi, I am simulating flow in a flume, the inlet boundary is velocity boundary, however every time I begin the simulation, the water level will increase and extend to the outlet boundary and never descend. For example, the fluid elevation I define at the inlet and outlet boundary is 50cm, but after the flow becoming steady the water level keeps 55cm and never change. How can I solve this problem?
1.At the outlet boundary, I have tried continuative, pressure and outflow boundary.
2.I have tried to increase the velocity slowly at the inlet boundary but it doesn't work.
3.I have put an obstacle at the top of the flume to avoid water rising but the simulation will exit anormally.
So who can figure out why?

Hi
Please send me the file : "prepin"
Jing_min is offline   Reply With Quote

Old   March 6, 2013, 04:52
Default
  #6
Member
 
bird
Join Date: Sep 2012
Posts: 42
Rep Power: 13
pyxbird is on a distinguished road
Quote:
Originally Posted by Jing_min View Post
Hi
Please send me the file : "prepin"
Title
This is a sample input file
$xput
remark='!! Remarks beginning with "!! " are automatically added and removed by FLOW-3D.',
remark='!! Do not begin any user added remarks with with "!! ". They will be removed',
twfin=250,
itb=1,
ifin=4,
ifvisc=1,
ifvis=4,
ifdynconv=1,
gz=-980,
ipdis=1,
idpth=1,
ifmu=1,
tpltd(1)=0.5,
$end
$limits
$end
$props
units='cgs',
tunits='c',
mu1=0.01,
fluid1='Water at 293 K',
thexf1=0.00018,
cv1=41820000,
tstar=100,
tl1=-0.149999999999977,
ts1=-0.149999999999977,
clht1=3350000000,
cvs1=21000000,
thcs1=221500,
rhofs=0.917,
teut=-273.15,
tmelt=-273.15,
ceut=0,
pcoef=0,
rhof=1.0,
sigma=73,
thc1=59700,
$end
$scalar
$end
&PCAP
/
&BCDATA
remark='!! Boundary condition X Min',
ibct(1)=6,
ubct(1, 1)=44.1,
fbct(1, 1)=1,
flhtbct(1, 1)=50,
remark='!! Boundary condition X Max',
ibct(2)=8,
flhtbct(1, 2)=50,
remark='!! Boundary condition Z Min',
ibct(5)=2,
/
&MESH
ntotal=1000,
nxcelt=2500,
px(1)=0,
px(2)=5000,
nycelt=1,
py(1)=0,
py(2)=1,
nzcelt=70,
pz(1)=0,
pz(2)=70,
/
$obs
remark='!! Component common parameters',
avrck=-3.1,
$end
$fl
nfls=1,
remark='!! Fluid Region 1',
fluidRegionName(1)='Water at 293 K',
fzh(1)=50,
pvoid=1.01325e+05,
iflinittyp=0,
$end
$bf
$end
$temp
$end
$motn
$end
$grafic
anmtyp(1)='dpth',
anmtyp(2)='f',
anmtyp(3)='vel',
$end
&HEADER
project='pre out',
/
$parts
$end
Documentation: general comments, background, expectations, etc.

#start tables:
#fluid1:
#blkmodts
#end blkmodts
#cv1
#end cv1
#cvnc
#end cvnc
#elastmodts
#end elastmodts
#emod1
#end emod1
#fs
#end fs
#mu1sr
#end mu1sr
#mu1t
#end mu1t
#poissonrts
#end poissonrts
#rhof
#end rhof
#shrmodts
#end shrmodts
#sigma
#end sigma
#thc1
#end thc1
#yield1
#end yield1
#end fluid1
#fluid2:
#cv2
#end cv2
#emod2
#end emod2
#mu2sr
#end mu2sr
#mu2t
#end mu2t
#rhof2
#end rhof2
#thc2
#end thc2
#yield2
#end yield2
#end fluid2
#end start tables
pyxbird is offline   Reply With Quote

Old   March 6, 2013, 04:55
Default
  #7
Member
 
bird
Join Date: Sep 2012
Posts: 42
Rep Power: 13
pyxbird is on a distinguished road
Quote:
Originally Posted by Jing_min View Post
Hi
Please send me the file : "prepin"
sorry, some errors emerge when I am uploading the prepin file, can you see it in my reply?
pyxbird is offline   Reply With Quote

Old   March 10, 2013, 07:23
Default
  #8
Senior Member
 
FHydro
Join Date: Jan 2013
Posts: 197
Rep Power: 13
flow_CH is on a distinguished road
Quote:
Originally Posted by pyxbird View Post
sorry, some errors emerge when I am uploading the prepin file, can you see it in my reply?
send me zip file of prepin.
flow_CH is offline   Reply With Quote

Old   November 7, 2013, 16:06
Default
  #9
New Member
 
Flowdy
Join Date: Nov 2013
Posts: 5
Rep Power: 12
Flowdy is on a distinguished road
It was happening to me also and I discover that the flow in given was bigger than flow out, then the volume of water will increase for sure… you could check it.


Another problem could be the delta time. When there is instabilities in the delta time or delta x the information of the volume flow will be lost and the volume so... I mean check the Courant-Friedrichs-Lewy condition
Flowdy is offline   Reply With Quote

Old   October 8, 2014, 04:09
Default
  #10
New Member
 
afghh
Join Date: Apr 2014
Posts: 2
Rep Power: 0
afgh is on a distinguished road
It was happening to me and i change the height of mesh with height free surface. and i will change the velocity inlet fluid elevation constant and outflow -pressure and fluid elevation constant. this work similar the ansys cfx.
and i dont know this is wright or wrong?
afgh is offline   Reply With Quote

Old   October 9, 2014, 02:46
Default
  #11
New Member
 
Join Date: Oct 2014
Location: Taiwan
Posts: 5
Rep Power: 11
Allenlin is on a distinguished road
Hi, Pyxbird

The case that you simulated is open channel flow. In flow-3d, the velocity is uniform distribution in velocity inlet boundary, but the velocity profile is parabolic distribution in channel if the flow is fully developed. Hence, they need to increase the flow area to maintain the same flow rate. There is why your result shows higher water level.
Allenlin is offline   Reply With Quote

Old   October 10, 2014, 03:31
Default
  #12
New Member
 
Join Date: Mar 2009
Location: green earth, blue ocean
Posts: 29
Rep Power: 17
hans_ina is on a distinguished road
I do the outlet as outflow and its work, i simulated without obstacle
hans_ina is offline   Reply With Quote

Old   November 11, 2014, 22:29
Default
  #13
New Member
 
jason
Join Date: Mar 2014
Posts: 19
Rep Power: 12
jason_sjtu is on a distinguished road
Quote:
Originally Posted by pyxbird View Post
Dear all,
Hi, I am simulating flow in a flume, the inlet boundary is velocity boundary, however every time I begin the simulation, the water level will increase and extend to the outlet boundary and never descend. For example, the fluid elevation I define at the inlet and outlet boundary is 50cm, but after the flow becoming steady the water level keeps 55cm and never change. How can I solve this problem?
1.At the outlet boundary, I have tried continuative, pressure and outflow boundary.
2.I have tried to increase the velocity slowly at the inlet boundary but it doesn't work.
3.I have put an obstacle at the top of the flume to avoid water rising but the simulation will exit anormally.
So who can figure out why?

hi ,perhaps you can try set water depth in initial condition instead of using fluid region.
jason_sjtu is offline   Reply With Quote

Old   November 21, 2014, 08:34
Default
  #14
New Member
 
jason
Join Date: Mar 2014
Posts: 19
Rep Power: 12
jason_sjtu is on a distinguished road
hi pyxbird,
the rising water level frustrate me a lot recently, although i tried several changes in the up_stream and down_stream boundary conditions.
Now, have you get the problem solved? if so ,could you please share the solution with me? thank you
George Klironomos likes this.
jason_sjtu is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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 Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Water subcooled boiling Attesz CFX 7 January 5, 2013 04:32
Water vapour condensation in CFX-5.7.1 hdj CFX 1 November 27, 2005 08:15
Separation phenomenon of water, droplet and air Raymond CFX 0 July 9, 2004 23:59
Terrible Mistake In Fluid Dynamics History Abhi Main CFD Forum 12 July 8, 2002 10:11
uptodate water distribution network fredius,magige,tanzanian,(e.a) Main CFD Forum 0 January 27, 2002 08:10


All times are GMT -4. The time now is 20:03.