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

Question about using total energy equation or thermal equation

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   May 6, 2013, 14:15
Question Question about using total energy equation or thermal equation
  #1
Senior Member
 
Anna Tian's Avatar
 
Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 15
Anna Tian is on a distinguished road
HI,

The tutorial tell that, for low-speed flow, thermal equation could be used instead of total energy equation to accelerate the computation. But how to know whether my case is 'low-speed' or not?

By the way, I'm simulating water. How to know whether the viscous term has to be included or not?
__________________
Best regards,
Meimei
Anna Tian is offline   Reply With Quote

Old   May 6, 2013, 15:19
Default
  #2
Senior Member
 
JuPa's Avatar
 
Mr CFD
Join Date: Jun 2012
Location: Britain
Posts: 361
Rep Power: 14
JuPa is on a distinguished road
Only use the total energy equation related to high speed flow if compressibility is important. I think (I invite anyone to correct me here) it's a speed around mach 0.3 and above.

If you're using water, and your flow is subsonic you won't have heat generation due to viscous work, so I wouldn't worry about it.
JuPa is offline   Reply With Quote

Old   May 6, 2013, 17:40
Question
  #3
Senior Member
 
Anna Tian's Avatar
 
Meimei Wang
Join Date: Jul 2012
Posts: 494
Rep Power: 15
Anna Tian is on a distinguished road
Quote:
Originally Posted by RicochetJ View Post
Only use the total energy equation related to high speed flow if compressibility is important. I think (I invite anyone to correct me here) it's a speed around mach 0.3 and above.

If you're using water, and your flow is subsonic you won't have heat generation due to viscous work, so I wouldn't worry about it.

My flow speed is not that high. Is there is a way (or criteria) to detect whether viscous term need to be included or not?
__________________
Best regards,
Meimei
Anna Tian is offline   Reply With Quote

Old   May 6, 2013, 19:58
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,665
Rep Power: 143
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
The easiest way is to run a model with and without it and you will then see if it makes a difference.
ghorrocks is offline   Reply With Quote

Reply

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
mass flow in is not equal to mass flow out saii CFX 12 March 19, 2018 06:21
Calculation of the Governing Equations Mihail CFX 7 September 7, 2014 07:27
What is the total energy for incompressible fluid? Harry Dong Main CFD Forum 12 February 4, 2006 01:55
Energy equation and Enthalpy Martin FLUENT 1 January 25, 2001 18:11
Info: Short Course On Thermal Design of Electronic Equipment Arnold Free Main CFD Forum 0 August 10, 1999 11:18


All times are GMT -4. The time now is 06:00.