Constant particle diameter

JEVA · June 16, 2020, 15:56

Dear all,
I am having issue with my tracked file result. I did a steady state simulation for droplet generation using Nukiyama-Tanasawa method. I put all the necessary parameters needed and used both boundary sampling and track file in the simulation. I selected Particle diameter, particle velocity and mass flow rate both for tracking and for the boundary sampling. However, at the end of the simulation, I was having just a constant value of the particle diameter whereas the other parameters gave me a range of results. What could be the problem?? I need to get the particle diameters at a particular location using boundary sampling but it is giving me only a constant particle diameter

cwl · June 17, 2020, 08:22

Injectors -> Injector 1 -> Values -> Parcel Streams

Parcel variable (diameter, temperature, velocity, etc) is the same for the whole parcel, thus default value of 1 results in problem you described while increasing this value will increase amount of parcels with different diameters, so the more Parcel Streams you set - the closer distribution of particle diameter to one you expect.

Keep in mind that increasing Parcel Streams also increases computational time, so you might want to decrase Point Inclusion Probability at the same time - to get less injection points per diameter value, but to represent your diameter distribution better with more parcels.

In other words instead of simulating motion of 100 balls of 1 mm (good tracking of behavior, but tells us only about behavior of 1 mm balls) - it's better to have 100 balls (or few times more) of varying diameter.

June 16, 2020, 15:56	Constant particle diameter	#1
JEVA New Member Vitalis Join Date: Jun 2020 Posts: 1 Rep Power: 0	Dear all, I am having issue with my tracked file result. I did a steady state simulation for droplet generation using Nukiyama-Tanasawa method. I put all the necessary parameters needed and used both boundary sampling and track file in the simulation. I selected Particle diameter, particle velocity and mass flow rate both for tracking and for the boundary sampling. However, at the end of the simulation, I was having just a constant value of the particle diameter whereas the other parameters gave me a range of results. What could be the problem?? I need to get the particle diameters at a particular location using boundary sampling but it is giving me only a constant particle diameter Last edited by JEVA; June 16, 2020 at 18:37.

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June 17, 2020, 08:22		#2
cwl Senior Member Chaotic Water Join Date: Jul 2012 Location: Elgrin Fau Posts: 436 Rep Power: 17	Injectors -> Injector 1 -> Values -> Parcel Streams Parcel variable (diameter, temperature, velocity, etc) is the same for the whole parcel, thus default value of 1 results in problem you described while increasing this value will increase amount of parcels with different diameters, so the more Parcel Streams you set - the closer distribution of particle diameter to one you expect. Keep in mind that increasing Parcel Streams also increases computational time, so you might want to decrase Point Inclusion Probability at the same time - to get less injection points per diameter value, but to represent your diameter distribution better with more parcels. In other words instead of simulating motion of 100 balls of 1 mm (good tracking of behavior, but tells us only about behavior of 1 mm balls) - it's better to have 100 balls (or few times more) of varying diameter.