CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > CFX

Modelling underwater sea current

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 23, 2016, 17:39
Default Modelling underwater sea current
  #1
Member
 
shaman
Join Date: Jul 2013
Posts: 37
Rep Power: 13
shaman is on a distinguished road
Hi all, i need to model thermal dilution of cold water discharge into seawater.
I have 3 question
1. How to model the seawater current which has a boundary layer like velocity profile... ie max at value A at surface and reduces as it reaches bottom. I have tried to model this as velocity inlet and outlet with same for domain initialization but the steady state analysis converge to a different solution. I need to maintain this current throughout the open sea domain. Can i use source.. if so how to maintain velocity profile.
2. My open sea domain is a hexagon 150m radius .. how to model translational periodics so my body of water represents d sea with underwater current mentioned above.
3. How to introduce scalar variable to track the behavior specific to the cold discharge water
shaman is offline   Reply With Quote

Old   May 23, 2016, 20:49
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,862
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
1) You will only get your intended velocity when you set the simulation up such that it gives the profile - in other words you have an appropriate turbulence model, turbulence conditions and other variables. So if you don't get the right profile it is because you have not set the model up such that it gives you the profile.

2) Make the matching parallel faces translational periodic pairs. So you will have 3 pairs for your hexagon.

3) Simple way: use an additional variable with convection and diffusion. But this will not account for the variation in material properties due to the difference in composition. If you want to account for this (to model things like the density difference due to salinity content) then use a multicomponent mixture.
ghorrocks is offline   Reply With Quote

Old   May 23, 2016, 20:55
Default
  #3
Member
 
shaman
Join Date: Jul 2013
Posts: 37
Rep Power: 13
shaman is on a distinguished road
Tqvm.. ghorrocks..
The sea current i m looking to model is less complicated as compared to prevailing sea current with the earth movement..
shaman is offline   Reply With Quote

Old   May 23, 2016, 20:57
Default
  #4
Member
 
shaman
Join Date: Jul 2013
Posts: 37
Rep Power: 13
shaman is on a distinguished road
I need a body of water moving at a velocity profile of my making vs depth.
The profile is from metocean study so it is reasonably accurate... and below 0.8ms-1.
shaman is offline   Reply With Quote

Old   May 23, 2016, 20:59
Default
  #5
Member
 
shaman
Join Date: Jul 2013
Posts: 37
Rep Power: 13
shaman is on a distinguished road
Isnt it possible to introduce a source term to that body of water... n the discharge water resolved as normal
shaman is offline   Reply With Quote

Old   May 24, 2016, 00:57
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,862
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
Yes, you can apply a source term. But if you apply a source term everywhere it will probably interfere with the flow around the region of interest to you. It could be better to put the source term on the periodic face only to pull the velocity to the profile.

If you know the velocity profile then why not forget about the periodic faces and just use an inlet with a prescribed velocity profile? Then you can specify the the profile easily.
ghorrocks is offline   Reply With Quote

Old   May 24, 2016, 01:46
Default
  #7
Member
 
shaman
Join Date: Jul 2013
Posts: 37
Rep Power: 13
shaman is on a distinguished road
Without source term wont the velocity at the discharge location diffuse due to large seabody. I could initialize the seabody with similar velocity profile. With no slip floor
shaman is offline   Reply With Quote

Old   May 24, 2016, 01:50
Default
  #8
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,862
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
If you have the correct turbulence model and conditions then the flow should not diffuse too much. This was my first point in the first post - you should try to make the physical model correct first, and then the need for a source term to enforce the desired velocity profile is greatly reduced.
ghorrocks is offline   Reply With Quote

Old   May 24, 2016, 02:30
Default
  #9
Member
 
shaman
Join Date: Jul 2013
Posts: 37
Rep Power: 13
shaman is on a distinguished road
Only have metocean data as ref for velocity profile.. have to make do with source term .. can the source term be velocity with function of height....and initialize sea body similarly
shaman is offline   Reply With Quote

Old   May 24, 2016, 07:26
Default
  #10
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,862
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
I do not understand what "metocean data as ref for velocity profile" means.

Yes, a source term can be a function of height (or just about anything else for that matter).
ghorrocks is offline   Reply With Quote

Old   May 24, 2016, 08:38
Default
  #11
Member
 
shaman
Join Date: Jul 2013
Posts: 37
Rep Power: 13
shaman is on a distinguished road
Metocean is d oceanographic study.. simulation conducted to simulate design criteria for specific return period ranging from 10... 50... 100 and in between.... it returns the most probable value with lowest potential of being exceeded
shaman is offline   Reply With Quote

Old   May 24, 2016, 08:38
Default
  #12
Member
 
shaman
Join Date: Jul 2013
Posts: 37
Rep Power: 13
shaman is on a distinguished road
Anyhow.. fluent has a function of fixed velocity... is this applicable
shaman is offline   Reply With Quote

Old   May 24, 2016, 21:06
Default
  #13
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,862
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
I do not know what the fluent fixed velocity function means. Please explain what it does.
ghorrocks is offline   Reply With Quote

Old   May 24, 2016, 21:09
Default
  #14
Member
 
shaman
Join Date: Jul 2013
Posts: 37
Rep Power: 13
shaman is on a distinguished road
It fixed the velocity in a particular domain.... feedback from support.. need to verify this and seek equivalent in cfx
shaman is offline   Reply With Quote

Old   May 25, 2016, 02:54
Default
  #15
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,862
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
If you fix the velocity field then there is no point doing CFD as the velocity is fixed.

You can fix the velocity using a source term in CFX.
ghorrocks is offline   Reply With Quote

Old   May 25, 2016, 03:03
Default
  #16
Member
 
shaman
Join Date: Jul 2013
Posts: 37
Rep Power: 13
shaman is on a distinguished road
Thnks sir... wil explore and revert...
shaman is offline   Reply With Quote

Old   May 30, 2016, 07:21
Default
  #17
Member
 
Mujahid Badshah
Join Date: Oct 2015
Posts: 32
Rep Power: 11
mujahidbadshah is on a distinguished road
you should use a velocity profile at the inlet boundary using profile BC'S option in CFX. or create a user function for changing inlet velocity against depth. See the post non uniform velocity at inlet.
mujahidbadshah 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
Current density visualisation (PEM fuel cell add-on module) pchoopanya FLUENT 10 August 21, 2023 15:33
PEM fuel cell modelling with and without current collector plates??? pchoopanya FLUENT 2 October 10, 2013 12:12
how simulating a water-particle current into sea doronzo FLUENT 0 September 30, 2011 15:52
Modelling a gaz-liquid counter current flow? Arou FLUENT 0 March 9, 2008 07:12
Modelling Jet Flow in a current Adrian FLUENT 3 January 12, 2006 11:42


All times are GMT -4. The time now is 22:13.