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

Particle Fate

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 19, 2000, 14:56
Default Particle Fate
  #1
Arturo Ortiz
Guest
 
Posts: n/a
Dear all.

I am simulating a system in which a liquid with diluted particles flows in normal direction to a sphere. I am interested in knowing how many particles are impacted in the sphere's surface. I've set up several simple cases, but no matter what I change ( density of the fluid or particle, velocity, gravity, etc ), fluent reports that no particles are impacted on the sphere. I think that for dense fluids that is correct because the fluid will deviate the particles when they approach the surface, but I've used air and the same happens. Any sugestions?, am I missing some physics? Thanks in advance
  Reply With Quote

Old   September 19, 2000, 21:33
Default Re: Particle Fate
  #2
Jin-Wook LEE
Guest
 
Posts: n/a
Dear Arturo Ortiz

As you may know, particle hits or does not hit the wall depending on the flow condition & particle properties. So, even though particle density is much higher than fluid density, particel MAY not reach the wall depending on the flow condition, because of the DRAG force of light gas.

The most important properties whcih have significant effect on the particle behavior are particle density and diameter. So, for your simple test, set very high value for particle diameter & particle density, e.g., 1.e4 micro-meter and 1.e5 kg/m3 or higher. I am sure, you can see that 'particle hits the wall(sphere)'. Please remember that this input is physically unrealistic for most case. I would like to say that flow condition is more important for particle behavior.

Sincerely, Jinwook

  Reply With Quote

Old   September 20, 2000, 12:07
Default Re: Particle Fate
  #3
Arturo Ortiz
Guest
 
Posts: n/a
Thanks for your comments, I've tried what you suggested; I used steel spheres (density >2.5)of 1 mm on air, even using a flat surface as target, but still can't get the particles impacted on the solid. I've tried as boundary conditions for the particles: escape and/or trap. I've made some simulations on complicated geometries and I obtained the particles impacted but not in simple ones.

Still wonder why.
  Reply With Quote

Old   September 21, 2000, 05:55
Default Re: Particle Fate
  #4
Jin-Wook LEE
Guest
 
Posts: n/a
Dear Arturo Ortiz

O.K. I myself am wondering.

But, density = 2.5 ? Maybe it's specific gravity. Density is, I think, at least 7000 kg/m3.

Sincerely, Jinwook

  Reply With Quote

Old   September 29, 2000, 08:06
Default Re: Particle Fate
  #5
dimitris
Guest
 
Posts: n/a
In case of interacting phases (main phase and dispersed one) the resulting flow field is affected by the motion of both phases. However, the flow when facing an obstacle will deviate trying to avoid it. So do the particles. The solution is to turn on the stochastic model (I suppose your case is turbulent) and set the tries at a number >20 to get a statistically representative particle motion. In this case particles will follow "strange", zig-zag paths, due to the assumed turbulent fluctuations and a number of them will hit the solid. This number should stay approximately the same at each iteration for the particles. If not, increase the number of tries.
  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
Particle Transport Modelling - Fate Diagnostics leeportnoff CFX 9 January 12, 2012 10:48
Particle fate "Integration error" ghorrocks CFX 5 December 13, 2011 12:03
Blood Damage Modelling via Particle Tracking in a Centrifugal Heart Pump scatman CFX 5 May 5, 2011 07:23
DPM UDF particle position using the macro P_POS(p)[i] dm2747 FLUENT 0 April 17, 2009 01:29
particle tracking collection tank Neser CFX 1 June 1, 2006 10:06


All times are GMT -4. The time now is 05:48.