CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

Buoyancy Analysis: Fluid Surface Boundary Condition

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 8, 2019, 10:26
Question Buoyancy Analysis: Fluid Surface Boundary Condition
  #1
New Member
 
Giovanni Fiorillo
Join Date: Mar 2018
Posts: 4
Rep Power: 8
ggfiorillo is on a distinguished road
Hello,

I hope I'm posting this in the right place. I am trying to model a tank full of fluid, I am starting with water since its properties are readily available. The walls of this tank are fixed and the top surface is exposed to air, which I will give a convection coefficient and an air temperature. The bottom surface is also given a "convection coefficient", a U-Value, along with a ground temperature.

What I am interest in seeing is how the heated walls create a buoyancy effect and the convection of the fluid you would get inside the tank as well as the temperature distribution throughout the fluid. All this to ask, in what way can i define the top surface? It is kind of like an opening but then I cannot specify a convection coefficient plus the fluid will just rise up and out of my tank and if i put a wall there I get an overflow error which i assume is because the water expands due to thermal expansion but has no where to go since i've mad every boundary condition a closed wall.

Could any advise on how to handle this? I know i could just model the air but that just seems like extra computation for something i'm not all that concerned about and figure there has to be a way around it.

Thanks in advanced for any help anyone can give!

Cheers,
Giovanni
ggfiorillo is offline   Reply With Quote

Old   January 8, 2019, 11:52
Default
  #2
Senior Member
 
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 6,760
Rep Power: 71
FMDenaro has a spectacular aura aboutFMDenaro has a spectacular aura aboutFMDenaro has a spectacular aura about
Quote:
Originally Posted by ggfiorillo View Post
Hello,

I hope I'm posting this in the right place. I am trying to model a tank full of fluid, I am starting with water since its properties are readily available. The walls of this tank are fixed and the top surface is exposed to air, which I will give a convection coefficient and an air temperature. The bottom surface is also given a "convection coefficient", a U-Value, along with a ground temperature.

What I am interest in seeing is how the heated walls create a buoyancy effect and the convection of the fluid you would get inside the tank as well as the temperature distribution throughout the fluid. All this to ask, in what way can i define the top surface? It is kind of like an opening but then I cannot specify a convection coefficient plus the fluid will just rise up and out of my tank and if i put a wall there I get an overflow error which i assume is because the water expands due to thermal expansion but has no where to go since i've mad every boundary condition a closed wall.

Could any advise on how to handle this? I know i could just model the air but that just seems like extra computation for something i'm not all that concerned about and figure there has to be a way around it.

Thanks in advanced for any help anyone can give!

Cheers,
Giovanni



In other words, you don't know the heat flux to set as Neumann condition at the surface?
FMDenaro is offline   Reply With Quote

Reply

Tags
boundary conditions, buoyancy driven flow, fluid surface, opening boundary, overflow

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
sliding mesh problem in CFX Saima CFX 46 September 11, 2021 08:38
Centrifugal fan j0hnny CFX 13 October 1, 2019 14:55
Fluid Domain moving with Rigid body Lloyd Sullivan CFX 3 August 17, 2018 10:58
Multiphase flow - incorrect velocity on inlet Mike_Tom CFX 6 September 29, 2016 02:27
Velocity vector in impeller passage ngoc_tran_bao CFX 24 May 3, 2016 22:16


All times are GMT -4. The time now is 06:08.