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

Single Flow Gravity effect

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

Like Tree2Likes
  • 1 Post By evcelica
  • 1 Post By ghorrocks

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 17, 2018, 07:49
Question Single Flow Gravity effect
  #1
New Member
 
Jack
Join Date: Apr 2018
Posts: 5
Rep Power: 6
Jack_Mate is on a distinguished road
Hello "CFDmates" how are you? So, here is the thing... I have a steady state, single phase, laminar, incompresible flow with a constant density and viscosity inside a microfluidics channel (my geometry has two parallel pipes, one at the upper side and one at the bottom side and they are connected to with a nozzle). I would like to consider the effect of the gravity in my model using the ANSYS CFX but without turn on the buoyancy option. How can I do it?

Thanks in advance!
Jack_Mate is offline   Reply With Quote

Old   July 17, 2018, 14:14
Default
  #2
Senior Member
 
Erik
Join Date: Feb 2011
Location: Earth (Land portion)
Posts: 1,122
Rep Power: 21
evcelica is on a distinguished road
It does not sound like gravity will have any effect at all, other than hydrostatic pressure on the walls, which you could just add in post processing.



Is the flow gravity driven or something?

You could set the the thermal expansion coefficient to zero (or a very small number 1e-30 if it rejects zero) then turn on buoyancy.
Sorry I don't fully understand what you are trying to model.
Jack_Mate likes this.
evcelica is offline   Reply With Quote

Old   July 17, 2018, 15:08
Default
  #3
New Member
 
Jack
Join Date: Apr 2018
Posts: 5
Rep Power: 6
Jack_Mate is on a distinguished road
Thank you for your reply! I do also believe that gravity plays a minor rolle in my case but I need to examine it. So, here are two images for better understanding

https://drive.google.com/file/d/12Su...ew?usp=sharing
https://drive.google.com/file/d/1NT0...ew?usp=sharing

I've been told that the fluid goes downwards because of the channel's geometry and not because of the gravity. Like in the outer space or something...
Jack_Mate is offline   Reply With Quote

Old   July 17, 2018, 23:00
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,267
Rep Power: 136
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
I am puzzled why you want to model buoyancy but do not want to turn the buoyancy model on. If you want to model buoyancy just turn the buoyancy model on.

If you don't like the built in buoyancy model you can always use a source term to do your own. The buoyancy term is just a simple source term.
Jack_Mate likes this.
__________________
Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.
ghorrocks is offline   Reply With Quote

Old   July 18, 2018, 04:31
Default
  #5
New Member
 
Jack
Join Date: Apr 2018
Posts: 5
Rep Power: 6
Jack_Mate is on a distinguished road
Hello! I just want to take into account the gravity without turning on the buoyancy since I do not have thermal phenomena and the fluid's density is constant.
Jack_Mate is offline   Reply With Quote

Old   July 18, 2018, 07:15
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,267
Rep Power: 136
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
If the fluid density is constant then gravity does nothing to the flow. All it does is add a hydrostatic head. If all you want is the pressure including the hydrostatic head then just turn buoyancy on and you will get it (in the absolute pressure variable). If gravity affects the flow somehow then you better explain how because nothing you have said so far would be affected by gravity.
__________________
Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.
ghorrocks is offline   Reply With Quote

Old   July 18, 2018, 17:04
Default
  #7
New Member
 
Jack
Join Date: Apr 2018
Posts: 5
Rep Power: 6
Jack_Mate is on a distinguished road
Thank you very much both of you! I did what evcelica said and my results were exactly the same! Now I have the proof I wanted!
Jack_Mate is offline   Reply With Quote

Reply

Tags
ansys cfx 18, fluid flow, gravity force, incompressible flow

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
Issues on the simulation of high-speed compressible flow within turbomachinery dowlee OpenFOAM Running, Solving & CFD 11 August 6, 2021 07:40
Review: Reversed flow CRT FLUENT 1 May 7, 2018 06:36
Eulerian multiphase flow- flow direction not comply with gravity mejahan CFX 11 April 17, 2017 05:19
Difference in flow distribution of single phase and multiphase analysis shivasluzz CFX 0 April 22, 2015 23:54
Free Surface Gravity Driven Flow Rupp Carriveau FLUENT 4 June 14, 2001 17:54


All times are GMT -4. The time now is 22:09.