CFD Online Logo CFD Online URL
Home > Forums > CFX

just calculating the energy equation

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

LinkBack Thread Tools Display Modes
Old   February 18, 2010, 06:01
Default just calculating the energy equation
New Member
Join Date: Nov 2009
Posts: 5
Rep Power: 10
peterle is on a distinguished road
Hey guys,

I'm working on a simulation of a heat sink. As I have only small temperature variations in the heat sink, I consider the physical properties to be constant -> one-way coupling between Navier-Stokes and energy equation.

I finished to simulate the hydrodynamics of the system and want to add the thermal analysis. I don't want to solve the N-S equations again. How can I tell CFX 12 to use my result from the hydrodynamic analysis and just calculate the energy equation? What do I have to consider regarding names of domains and boundary conditions? Are they supposed to be the same? What happens if I change the grid (Perhaps the grid has to be finer for the thermal analysis)? Before I was just modeling the flow channels, now there is a massive domain of solid material involved? Is there a problem due to the fact, that I add domains to the simulation?

It would be nice if someone could share his experiences with this kind of two-step approach in CFX
peterle is offline   Reply With Quote

Old   April 21, 2010, 16:48
New Member
J. D. Aurand
Join Date: Apr 2010
Posts: 13
Rep Power: 9
JDA is on a distinguished road
If I understand you correctly, you solved the Navier-Stokes equation without regard to heat transfer. Now you want to solve both the fluid flow and the heat transfer, but don't want to start from scratch, is that right?

What you need to do is edit your .def file and include the energy components (both solving the heat transfer and including heat transfer BCs, the default heat transfer BC is adiabatic wall). Write a new .def file (probably want a different name to keep things separate) and setup a new run. In the define solver run window, check the initial conditions box and browse to your .res file from the fluid flow. You can use a different (more or less refined) mesh and it will interpolate the values onto the mesh. I don't think you can add a domain, but it's worth a shot to give it a try. I usually model all the domains and just apply walls to the solid surfaces if heat transfer is not being studied initially.
JDA is offline   Reply With Quote

Old   April 21, 2010, 22:32
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 14,070
Rep Power: 109
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
An alternate approach is you can use expert parameters to turn the fluids solver off and continue running. This way you will only solve the heat equation with the fluid field fixed so the simulation will proceed much faster.
ghorrocks 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
Calculation of the Governing Equations Mihail CFX 7 September 7, 2014 06:27
ATTENTION! Reliability problems in CFX 5.7 Joseph CFX 14 April 20, 2010 15:45
Viscosity and the Energy Equation Rich Main CFD Forum 0 December 16, 2009 15:01
SIMPLE and energy equation convergence Fabio Main CFD Forum 0 June 1, 2007 06:06
question about energy equation zhou FLUENT 0 February 24, 2004 00:55

All times are GMT -4. The time now is 18:52.