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

Negative y-velocity heated channel fluent with natural convection

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 8, 2021, 13:01
Default Negative y-velocity heated channel fluent with natural convection
  #1
New Member
 
Nathan Hale
Join Date: Oct 2021
Posts: 2
Rep Power: 0
not_fluent_in_fluent is on a distinguished road
Hello,

I've been having an issue that hopefully you all can help me solve. I'm fairly new to using fluent and so I wanted to start with a simple, heated vertical channel with flow driven by natural convection. I am not using the Boussinesq approximation because I am using the "incompressible-ideal-gas" option for density (which was described to me as the one to use if I don't want the pressure affecting the density but do care about the density being a function of temperature).

For my boundary conditions, I have a pressure inlet at the bottom and a pressure outlet at the top (both with 0 gage pressure). Along the vertical sides, I have a heated wall with no slip.

My issue is that I am getting positive flow up along the walls in the boundary layers, but then towards the center of the channel, the flow reverses and I am getting a negative velocity in the y-direction.

I feel like this (the negative y-velocity) shouldn't be happening assuming that the air is quiescent outside of the boundary layer. Do you guys have any suggestions? I've already looked at a bunch of the forum posts here, in addition to different videos online. I havenít been able to correct this, and so Iím at a loss. If you guys could point me in the right direction.

Sidenote: It feel like Fluent is trying to drive the average velocity through the channel to zero. The picture of the Matlab code is me calculating the average velocity over the top, middle, and bottom of the channel.

I'll include some pictures that hopefully help show what I described earlier.

https://docs.google.com/document/d/1...it?usp=sharing

I appreciate all your help!
not_fluent_in_fluent is offline   Reply With Quote

Old   December 2, 2021, 12:59
Default Solution
  #2
New Member
 
Nathan Hale
Join Date: Oct 2021
Posts: 2
Rep Power: 0
not_fluent_in_fluent is on a distinguished road
I figured out my issue...

In order to use the "incompressible ideal gas," I needed to specify the operating density as the density of the fluid at the inlet. This results in positive velocities all the way around. This solution worked for a heated channel as well as a simpler heated vertical plate.
not_fluent_in_fluent is offline   Reply With Quote

Reply

Tags
fluent, heated wall, natural convection, vertical channel

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
natural convection in vertical channel Arjun123 FLUENT 11 November 23, 2014 10:09
Setting up heat transfer beetween wall heated zone and flow channel zone in Fluent tafa Fluent Multiphase 0 May 25, 2014 06:08
FLUENT 6.3: how to model natural convection in square cavity partially heated lbmagis FLUENT 0 November 19, 2012 10:53
[blockMesh] BlockMesh FOAM warning gaottino OpenFOAM Meshing & Mesh Conversion 7 July 19, 2010 15:11
[blockMesh] Axisymmetrical mesh Rasmus Gjesing (Gjesing) OpenFOAM Meshing & Mesh Conversion 10 April 2, 2007 15:00


All times are GMT -4. The time now is 16:07.