KR28: What is the difference between particle parcel and stream?
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In Unsteady DPM: It is very expensive to track each individual particle in a particle flow system. Instead of tracking each particle, FLUENT tracks Parcel. Parcel contains particles with same properties including diameter, velocity and position. The behavior of each parcel is determined by the behavior of the particles inside. Fluent tracks parcels and number of particles in a parcel can be obtained using macro p->number_in_parcel. The number of particles in each parcel can be a fractional number. Streams are defined for injecting the parcels in the computational domain. `N` streams means `N` locations of parcel injection Stream mass flow rate, and number of particles in a parcel are related as: Number of particles in a parcel = (Stream mass flow rate*Injection time interval)/(Mass of single particle) Number of particle streams that you specify is nothing but, the number of parcels that get injected after each injection time interval In Steady DPM: Number of particles in parcel is not valid for steady tracking. Instead there is "strength" which is essentially number particles in parcel / second and is calculated as: Strength = (Stream mass flow rate)/(Mass of single particle) Clarification: FLUENT user`s documentation mentions "particles" everywhere, when it should be actually parcels. |
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