[aizhanmardiyeva]

Hi, I'm working with DPM injections.
1) Exactly, used surface case, and i chose inlet where 4018 surfaces. But i can not control the number of particles. I'm using unsteady DPM.
My questions:
How i can control the number of particle?
2) When i look to summary there are shown that
Total number of parcels : 120458
Total number of particles : 4.855374e-06
How number of particle could be non integer number?
What is parcel mean?
What is the relationsheap between particle and parcel
3) When i look to the Particle Mass Concentration there are shown results in -15 th degree.

[vinerm]

It appears that you have left the injection properties as default. DPM requires following inputs

1. Positions for the particles. In your case, that is provided by the centers of the faces of the inlet
2. Velocities of the particles. Default is 0. You have to provide a number. It could be left as 0 as well but that will put a lot of drag on the incoming fluid.
3. Flow rate for the particles. Default is either 0 (old fluent versions) or a very small number (new versions).
4. Diameters for the particles. Default is very small number or 0 (older versions)

Based on the above inputs, number of parcels are decided. Since you have 4018 mesh faces on the inlet, 4018 parcels will be injected every Lagrangian time-step. You can control this number but you do not need to. Total number of particles depend upon the diameter and flow-rate of particles. Mass of one particle is given by the product of its volume (particles are always spheres in DPM) and its density (given in material panel). Total number of particles injected in one time-step is ratio of the product of the mass flow rate given in the injection and the particle time-step to the mass of one particle, i.e.,

Number of particles injected in a time-step =

If the flow rate is less or set to default value, then you would expect very small number of particles and equally small amount of concentration.