Hi,

Would you please explain the DPM parcel concept? I could not find anything about it in the Manual and I do not have a clue about it. All the manual talks about is the equations of a SINGLE particle. I simulate a supersonic nozzle with water paticles injected at inlet, steady state flow. I have difficulty understand the parcel concept in general. Also, how does it relate to particle stream and mass flow of injection?

thanks a lot

Hi,

FLUENT represents the true number of particles in a spray by a number of "parcels" (groups of particles) which have similar properties (diameter,velocity etc..) as each particle.

The thing to realise is that the mass-flow of the parcel is equal to the mass-flow of the group of particles, to account for their number on the momentum exchange with the gas phase.

It helps reduce the computational time as you are dealing with less calculations but still getting the diameters and velocities out. Generally the more parcels you use the more accurate the solution.

Is that clear?

Regards,

Paul Hutcheson University of Surrey

I would like to add to what Paul has written.

Particle parcels are analogous to seeding particles in flow measurements. Seeding particles have uniform diameter, spherical shape, low loose weight, and high melting temperature and when introduced they follow flow stream lines, well... almost! They are expected to have near-zero buoyancy.

In measurement techniques, the velocities of these particles are considered to be the velocities of the fluid packets surrounding them.

Hope this clarifies the concept still better.

Best wishes Prasad

[viva]

Hi , I just read the concept of DPM particle parcels and trying to understand it. Does it means that each parcel represents many particles (one is being tracked and others are just psuedo). If that is the case then how many particles are there in the parcel and can the user change the number of particles in one parcel.

Thanks in advance

[sajeesh]

hi

I have a 25 micrometer diamter particles.I want to inject exactly three number of particle into the fluid flow.How can i do that.Density of particle is 998 kg/m3.

If i know the number of particle number in parcel .Is it the total number of particle that i inject to the flow..please help me

sajeesh

[unnikrishnan]

I did a steady state DPM. I requested the summary and it showed that no of parcels=3304 and no of particles=900. How is this possible? I used 60 as No of particle streams. PLease help me out

[Antanas]

Originally Posted by unnikrishnan

I did a steady state DPM. I requested the summary and it showed that no of parcels=3304 and no of particles=900. How is this possible? I used 60 as No of particle streams. PLease help me out

Hmm... I may be wrong, but assume that total mass of particles is 1 kg. And you request 1000 parcels. Then mass per parcel is 1 g. If mass of your particle is 2 g, then each parcel represents 0.5 of particle and total number of particles will be 500. So 1000 parcels and 500 particles.

[unnikrishnan]

How's that possible? If one parcel represent half of a particle, another parcel represents the remaining half, it will be impossible to locate that kind of a particle no? And this totally destroys the idea of parcel concept in Fluent. As I believe, one parcel will contain number of particles because it's computationally impossible to track very large no of particles.
If what you say is correct,for example if i have 50 parcels and 1 particle how will i calculate the position of that single particle?? Even if fluent averages the properties of all 50 parcels to get the property of 1 particle, the particle tracking will show 50 parcels in the window and it is gonna be a wrong visualization of the spray...