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-   -   URGENT!!!!!!!!!!!!total numebr of particles (https://www.cfd-online.com/Forums/fluent/39726-urgent-total-numebr-particles.html)

 antonietta February 20, 2006 11:05

URGENT!!!!!!!!!!!!total numebr of particles

hi, I'd like to calculate the numebr of particles which are injected from a surface, when I apply the discrete phase model defining an ejection released fropm a specific surface. I mean, if I have for example 8 tracked stream, does it mean that I have 8 particles? And in this case, 8 particle for each stream or in total? thanks

 HS February 20, 2006 11:19

Re: URGENT!!!!!!!!!!!!total numebr of particles

In the discrete phase model your particles are represented by parcels. A parcel will appear as a "particle" if you plot it in the domain, but is really a representative for a number (or even a fraction) of real particles. This is depending on the total mass flow-rate and initial diameter/density you choose. You can color your particle traces by the number of particles per parcel while post-processing. If you are doing unsteady particle tracking (or using a spray breakup model), FLUENT will inject one parcel per injection stream and timestep. If doing steady-state simulations, a number of parcels equal to the number of injection streams will be followed throughout the domain. Note that stochastic tracking may alter the number of computational parcels (but not the number of real particles).

 yooceframandi February 20, 2006 14:04

Evaporataion in DPM

Dear friend;

I use DPM but i have not "evaporated" fate in report window,while the temperature of system is more than droplet vaporization temperature.

and the diameter of droplets is reducing!!!

what is the problem?

 HS February 21, 2006 04:15

Re: Evaporataion in DPM

Most probably, there is no problem. Once again, remember that it is not individual droplets you track in the domain but computational parcels. Thus, one parcel could represent many droplets. If vaporization is going on, FLUENT will calculate the mass loss due to vaporization according to the heat- and mass transfer laws used and thus the diameters will decrease. However, a single parcel can only represent droplets of a single set of properties, so all diameters will decrease the same. This means that the evaporation fate will only happen to your parcel once all droplets have evaporated, which they will of course do at exactly the same instant in time.

To summarize: You track a parcel that represent many droplets, but all with the same properties. Just as if it was a single droplet, the diameter will decrease during evaporation. The fate "evaporated" in the report summary only applies to parcels that have been fully evaporated within the domain.

/HS

 yooceframandi February 21, 2006 05:21

Re: Evaporataion in DPM

DEAR HS;

thanks for useful help.

can i patch a mass of droplet in domail aithout injection?

and can i define a particle with solid content? i mean: solid+liquid (wet-solid).

i mean can i use combusting particle?

regards

 HS February 21, 2006 08:11

Re: Evaporataion in DPM

* can i patch a mass of droplet in domail aithout injection?

I am no expert but I don't think this is possible with the discrete phase model in FLUENT. You would have to create injections and modify them through UDFs instead I guess.

* and can i define a particle with solid content? i mean: solid+liquid (wet-solid).

Yes that is possible in the Materials panel for your discrete phase species.

* i mean can i use combusting particle?

Yes. There are even pre-defined particle types that are suited for combustion and also wet combustion. Look in the manual for more info on this!

Good luck!

/Henrik

 MANOJKUMAR February 21, 2006 09:01

Re: Evaporataion in DPM

Hello Sir, I asked one question what is the composition of the LDO and how to create PDF file for that. In my case 350 mm is dia of air and injection is given at center of this hole. So how to find the velocity of this air. I give velocity of injection is 100m/s and dia is 0.3 and flow rate is 0.0059 kg/sec. Any method to find this calculation. Thanking u

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