CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Unrealistic flows in a natural ventilation model

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   September 9, 2021, 10:20
Default Unrealistic flows in a natural ventilation model
  #1
New Member
 
Ben Simpson
Join Date: Dec 2019
Location: UK
Posts: 22
Rep Power: 4
b.simpson is on a distinguished road
Hi all,

I have a natural ventilation model which comprises of a small simple room with a couple of heat sources inside and two sections on either side of the room acting as the external environment. I am using OpenFOAM v8 running buoyantSimpleFoam with RNG K-Epsilon.

When I visualize the U field in paraview, the air flows seem to be flowing from the top atmospheric boundary down to the ground on both sides of the building. My initial guess is that I need some sort of coefficient to control how the internal pressure matches the set external pressure. I know Phoenics has a control where you can add either a linear or quadratic coefficient to acheive this control. Unfortunately I do not now how, providing I need to, acheive this in OpenFOAM.

I have attached an image of the flows in paraview which hopefully shows the problem that I am trying to explain. I have also attached a compressed version of my model, if that is needed.

I have seen the use of a p0 value in some of the p files and not sure if I should be using this.

Hopefully someone will be able to help with this issue.

Kind regards.

Here is my p file:
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [1 -1 -2 0 0 0 0];

internalField   uniform 1e5;

boundaryField
{
    "xmin_South|xmin_North|xmax_South|xmax_North|ymin|ymax|zmin|Ceiling|Floor|East_Wall|North_Wall|South_Wall|West_Wall|Computer|Person|zmax_north|zmax_south|zmax_ceiling|North_Window|South_Window|xmin_Centre|xmax_Centre"
    {
        type            calculated;
		p0              $internalField;
        value           $internalField;
    }
	
	#includeEtc "caseDicts/setConstraintTypes"
}

// ************************************************************************* //
Attached Images
File Type: jpg U_flows02.jpg (69.9 KB, 23 views)
Attached Files
File Type: gz RNG_KE.tar.gz (68.2 KB, 8 views)
b.simpson is offline   Reply With Quote

Old   September 21, 2021, 12:56
Default
  #2
New Member
 
Ben Simpson
Join Date: Dec 2019
Location: UK
Posts: 22
Rep Power: 4
b.simpson is on a distinguished road
By any chance does anyone know how to fix this issue and achieve more realistic flows using the RNG K-e model?
b.simpson is offline   Reply With Quote

Old   January 31, 2022, 10:07
Default
  #3
New Member
 
Ben Simpson
Join Date: Dec 2019
Location: UK
Posts: 22
Rep Power: 4
b.simpson is on a distinguished road
Does anyone have any suggestions as to how to fix this model?
b.simpson is offline   Reply With Quote

Old   January 31, 2022, 10:36
Default
  #4
Senior Member
 
Yann
Join Date: Apr 2012
Location: France
Posts: 468
Rep Power: 18
Yann will become famous soon enough
Hi,

First thing I would try: use 2nd order schemes in fvSchemes instead of 1st order (upwind)

For buoyant flows, using first order schemes can cause this kind of behavior.

I hope this helps,
Yann
Yann is offline   Reply With Quote

Reply

Tags
buoyantsimplefoam, openfaom-8, rng k-epsilon

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
Table bounds warnings at: END OF TIME STEP CFXer CFX 4 July 16, 2020 23:44
[swak4Foam] swakExpression not writing to log alexfells OpenFOAM Community Contributions 3 March 16, 2020 18:19
Is it possible to model natural convection in a 2D horizontal model in fluent caitoc FLUENT 1 May 5, 2014 13:32
which model is suitable for natural ventilation? HVAC FLUENT 5 December 27, 2005 20:29
natural ventilation on buildings bill FLUENT 2 September 30, 2004 07:43


All times are GMT -4. The time now is 02:39.