CFD Online Logo CFD Online URL
Home > Forums > CFX

Calculating Loss Coefficients for a porous media

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

LinkBack Thread Tools Display Modes
Old   October 22, 2015, 18:22
Default Calculating Loss Coefficients for a porous media
New Member
Join Date: Jul 2015
Posts: 19
Rep Power: 3
CFX_Beginner is on a distinguished road

I need help on calculating the right Loss Coefficient for a porous media.

In the grafic down below you can see the setup and the equation that's causing the pressure loss in the porous media.

I prescribe dp/dx and with the help of the equation I want to calculate the right Loss Coefficient, so the porous media is performing exactly this dp/dx.

I get all the other variables I need to solve the equation from CFD Post, loading a finished simulation with the same parameters as the one I want to do except for the Loss Coefficient and I set the Permeability (Kperm = 1 mē).

The problem I have is that when I calculate the Loss Coefficient with that equation and run the simulation, it's not achieving the dp/dx that I calculated the Loss Coefficient for.
That means I'm making some small mistake during the calculation process...

For example:
The Loss Coefficient I calculated is 250.
The correct one that achieves the dp/dx I prescribed is 540, which I found out by manual testing.

Taking into account that the range of the result is nearly the same, I thought that the mistake is that I didn't take the right value for some variable in the equation.
Sadly there is no documentation from Ansys Help on where those variables are taken exactly.

At the moment I get the Density, Dynamic Viscosity, Velocity Component Ux and the Velocity |U| from a Volume Average of the porous media.

I hope i explained my problem properly and some of you are able to help me.

CFX_Beginner is offline   Reply With Quote

Old   October 23, 2015, 18:42
Senior Member
Join Date: Jun 2009
Posts: 600
Rep Power: 14
Opaque is on a distinguished road
Not sure what wall boundary conditions you are applying, but I would use Free Slip on the walls so you can get a 1-D porous media model that matches the equation you are showing in a particular x_i

Hope the above helps,
Opaque is offline   Reply With Quote

Old   October 24, 2015, 20:16
New Member
Join Date: Jul 2015
Posts: 19
Rep Power: 3
CFX_Beginner is on a distinguished road
Just tested it with Free Slip Wall, but the overall problem is still the same. The pressure loss in the simulation is not the same as the one in the calculation.

I'm sure I use the right variables for the equation so there must be a mistake in the overall understanding of the equation or the "transport" from the equation into the simulation.
CFX_Beginner is offline   Reply With Quote


Thread Tools
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 On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Porous media setup issues in Fluent Bernard Van FLUENT 29 January 26, 2017 05:09
CFD by anderson, chp 10.... supersonic flow over flat plate varunjain89 Main CFD Forum 17 February 11, 2015 10:47
Linear and quadratic loss coefficients of porous domain LD696 CFX 1 May 21, 2014 15:08
Directional Loss Porous Media tehzap CFX 0 December 2, 2013 11:29
porous media: Fluent or Star-CD? Igor Main CFD Forum 0 December 5, 2002 16:16

All times are GMT -4. The time now is 21:53.