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

Mass flow rate

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 12, 2004, 06:22
Default Mass flow rate
  #1
Neser
Guest
 
Posts: n/a
Hi there,

In CFX5.6 post, when I used calculter panel to calculate pressure, temprature, mass flow rate, velocity, etc. I asked it to calculate all inlet condition, there was no any problems. However, when I asked it to calculate the out put conditions, I got the following answers:

Mass flow rate 0.0 max. Velocity 5.698 m/s

How I can have a velocity with out mass folw rate!!!. How outlet mass flow rate is zero, while inlet mass flow rate is 19.8198 kg/s.

please help me, what is the problem!!
  Reply With Quote

Old   February 12, 2004, 16:28
Default Re: Mass flow rate
  #2
Glenn Horrocks
Guest
 
Posts: n/a
Hi Neser,

If the flow is leaving the domain it is a negative mass flow rate. Velocity magnitude is a scalar, and so is always positive. I suggest you find the minimum of the mass flow rate instead and you should get a sensible answer.

Glenn
  Reply With Quote

Old   February 12, 2004, 23:43
Default Re: Mass flow rate
  #3
Neale
Guest
 
Posts: n/a
From previous posts it looked to me like you are attempting multiphase calculations. Maybe the volume fraction is zero at your outlets for the phase with a 5.68 m/s velocity?

Neale
  Reply With Quote

Old   February 13, 2004, 05:03
Default Re: Mass flow rate
  #4
Neser
Guest
 
Posts: n/a
Yes, It two phase flow, water and air. However, the program gave me zero mass flow rate for the two outlets I have this for total, water and air. It is imposible to have zero volume fration for all fluids at outlets.
  Reply With Quote

Old   February 14, 2004, 00:27
Default Re: Mass flow rate
  #5
Jeff
Guest
 
Posts: n/a
If you look at a plot of the vectors are they all leaving the domain? For both phases?

It is possible to have a finite maximum velocity (which is direction independent and indicates the maximum vertex velocity on the plane, not the mean signed velocity) and still have an eddie at the outlet plane which results in a zero mass flow rate. Thus, even though the maximum velocity is 7.6 m/s, there may be an equal vector in the opposite direction (which will also be positive) resulting in a net zero mass flux.

Just a thought.

Jeff
  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
Particle Injection Mass Flow Rate and Position leonozx FLUENT 3 March 9, 2018 09:58
CFX turbo - Mass flow rate Vashishth Patel CFX 7 April 3, 2014 20:33
Mass flow rate at the outlet tejasvikrishna FLUENT 2 May 25, 2013 02:42
negative global mass flow rate Gimli FLUENT 0 April 21, 2006 07:17
mass flow rate error Masood FLUENT 0 May 22, 2005 00:32


All times are GMT -4. The time now is 03:04.