How to "delete" material particles in fluid region?

natalie26 · January 30, 2013, 07:14

Hello everybody,
i need some help on lagrangian particle simulations.

Does anyone know if there is a possibility to "delete" particles after a certain residence time?
My modell is a 2 phase (VOF) flow with a free surface. Additionally to air
i´m trying to inject material (liquid) droplets (lagrangian) into the fluid region. But they should "disappear" in the moment they reach the water surface (Euler).

Can anyone help me?
Thanks!

siara817 · January 30, 2013, 11:32

Is the water surface is as a boundary then you need to activate escape in that boundary.

natalie26 · January 31, 2013, 02:27

Hey, thanks for your answer!
No, the water surface is not a boundary its just the free surface between air and water. Actually in my simulation I want to increase the waterlevel.
But because there is no mass transfer from Lagrangian to the Eulerian phase of water I want the droplets that are raining on this surface to disappear or escape and, instead of that I added source terms (euler water) above the water surface. So that there is added 50 kg of water per second.
The result is quite good at first (The mass of water increases, due to the mass source 50 kg/s) but when the droplets arrive the water surface... The mass of water increases somehow different, but I don´t really understand whats happening there. The mass flow rate of the droplets is also 50 kg/s. But the mass of eulerian water increases about 80 kg/s. Any ideas?
Thanks!
natalie

siara817 · January 31, 2013, 02:42

Are you sure, if it is converged?

natalie26 · January 31, 2013, 03:02

Yes,
at the moment i´m trying it on a simplified model. Its´a closed cube with 1x1x1m all boundaries are walls.
The water level is at 0.3 m. I added the source term for water and a sink term for air (= -watersource) and ran it for 1 second.
This simulation converged.
In the next step I added the injector at the top wall and the residuals at least don´t diverge

I´m just trying how it works, because my real model has about 3 mio. cells which is too time-consuming to just "try".

January 30, 2013, 07:14	How to "delete" material particles in fluid region?	#1
natalie26 New Member Join Date: Feb 2012 Posts: 8 Rep Power: 14	Hello everybody, i need some help on lagrangian particle simulations. Does anyone know if there is a possibility to "delete" particles after a certain residence time? My modell is a 2 phase (VOF) flow with a free surface. Additionally to air i´m trying to inject material (liquid) droplets (lagrangian) into the fluid region. But they should "disappear" in the moment they reach the water surface (Euler). Can anyone help me? Thanks!

January 30, 2013, 11:32		#2
siara817 Senior Member siamak rahimi ardkapan Join Date: Jul 2010 Location: Copenhagen, Denmark Posts: 220 Rep Power: 17	Is the water surface is as a boundary then you need to activate escape in that boundary. __________________ Good luck Siamak

January 31, 2013, 02:42		#4
siara817 Senior Member siamak rahimi ardkapan Join Date: Jul 2010 Location: Copenhagen, Denmark Posts: 220 Rep Power: 17	Are you sure, if it is converged? __________________ Good luck Siamak

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January 31, 2013, 02:27		#3
natalie26 New Member Join Date: Feb 2012 Posts: 8 Rep Power: 14	Hey, thanks for your answer! No, the water surface is not a boundary its just the free surface between air and water. Actually in my simulation I want to increase the waterlevel. But because there is no mass transfer from Lagrangian to the Eulerian phase of water I want the droplets that are raining on this surface to disappear or escape and, instead of that I added source terms (euler water) above the water surface. So that there is added 50 kg of water per second. The result is quite good at first (The mass of water increases, due to the mass source 50 kg/s) but when the droplets arrive the water surface... The mass of water increases somehow different, but I don´t really understand whats happening there. The mass flow rate of the droplets is also 50 kg/s. But the mass of eulerian water increases about 80 kg/s. Any ideas? Thanks! natalie

January 31, 2013, 03:02		#5
natalie26 New Member Join Date: Feb 2012 Posts: 8 Rep Power: 14	Yes, at the moment i´m trying it on a simplified model. Its´a closed cube with 1x1x1m all boundaries are walls. The water level is at 0.3 m. I added the source term for water and a sink term for air (= -watersource) and ran it for 1 second. This simulation converged. In the next step I added the injector at the top wall and the residuals at least don´t diverge I´m just trying how it works, because my real model has about 3 mio. cells which is too time-consuming to just "try".