CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

Mass flow rate in DPM

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

Reply
 
LinkBack Thread Tools Display Modes
Old   January 8, 2002, 01:56
Default Mass flow rate in DPM
  #1
Christian
Guest
 
Posts: n/a
Hi.

I use a single point injection in a axisymmetrical case. In the Fluent Help it says that the mass flow rate is defined per 2*PI radians. I interpret this as if I have a total mass flow of say 2kg/sec, then I should write the mass flow rate as 2/(2*PI)=0.318kg/sec in the panel.

But when I try to summarise the DPM phase in report/volume integrals/sum then I just get 0.318kg/sec instead of 2kg/sec. Clearly I have misinterpreted something. Can anyone help ?

Cheers Christian
  Reply With Quote

Old   January 8, 2002, 03:42
Default Re: Mass flow rate in DPM
  #2
Guohui Wang
Guest
 
Posts: n/a
I think you should define the mas flow rate as 2kg/s directly.

guohuiwang
  Reply With Quote

Old   January 8, 2002, 05:31
Default Re: Mass flow rate in DPM
  #3
Alain
Guest
 
Posts: n/a
Hi christian

when you use an axisymetric grid, the "depht" of the volume is equal to 1 radian.

So if you inject particle you have to divide the real massflow by 2 PI in order to have the correct mass, momemtum and heat source from DPM.

Of course when you use integral value in the report you should multiply these values by 2 PI because FLUENT give you the integral value on a 1 radian slice.

I think it might be possible to change this depth in the reference value panel.

Best regards

Alain
  Reply With Quote

Old   January 9, 2002, 04:28
Default Re: Mass flow rate in DPM
  #4
Christian
Guest
 
Posts: n/a
Thats what I would like to do, but is the manual incorrect then ?

Cheers Christian
  Reply With Quote

Old   January 9, 2002, 04:30
Default Re: Mass flow rate in DPM
  #5
Christian
Guest
 
Posts: n/a
Hi.

When I in the report\volume integrals choose volume, Fluent calculate the correct total volume and not the volume per 2*PI even though Fluent says that: "The volume of a surface is computed by summing the volumes of the cells that comprise the zone". Fluent then knows that because this case is axisymm. It can calculate a volume based upon a 2D model.

I then choose the field variable as DPM and option: Sum. Now I would expect that because Fluent says: "The sum of a specified field variable in a cell zone is computed by summing the value of the selected variable at each cell in the selected zone" it still is based upon the correct volume and not on volume per 2*PI.

But as I have mentioned I the previous mail, the manual clearly says that the mass flow rate input should be based per 2*PI.

I am still confused how to interpret these inputs and outputs. Especially because when I in the input use the total mass flow and not mass flow per 2*PI, the result looks as expected.

Cheers Christian
  Reply With Quote

Old   January 10, 2002, 19:30
Default Re: Mass flow rate in DPM
  #6
Jin-Wook LEE
Guest
 
Posts: n/a
1. Guohui's answer is correct. Concept of DPM injection is based on point injection. The concept of '2*PI' is for continuos phase(gas phase), not for DPM.

2. Fluent 4.5 have used 1 radian, not 2*PI radian.

Sincerely, Jinwook

  Reply With Quote

Old   January 11, 2002, 01:42
Default Re: Mass flow rate in DPM
  #7
Christian
Guest
 
Posts: n/a
Hi Guohui, Jinwook and Alain.

Thank you for your time and answers. It has been helpful.

Cheers Christian
  Reply With Quote

Reply

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
CFX turbo - Mass flow rate Vashishth Patel CFX 7 April 3, 2014 20:33
UDF to measure Mass Flow Rate a.lynchy Fluent UDF and Scheme Programming 21 February 15, 2014 02:18
Mass flow rate of the DPM mass sourse ?? Rhinocao FLUENT 3 January 21, 2011 12:10
mass flow rate not conserved in turbomachine, interface defined wrong? wildli FLUENT 1 March 24, 2010 20:23
mass flow rate error Masood FLUENT 0 May 22, 2005 00:32


All times are GMT -4. The time now is 08:03.