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UDF codes in investigating the effect of particle electrostatic force

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Old   March 26, 2015, 23:13
Thumbs up UDF codes in investigating the effect of particle electrostatic force
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I'm currently doing a simulation on inhaler to investigate the effect of electrostatic force on particles using DPM UDF. Any one has that experience in writing that codes? I've totally no idea how to do that.
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Old   March 26, 2015, 23:30
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Interesting topic! What distance (orders of magnitude) are these electrostatic forces acting across? Are you interested in particle-particle or simply particle-wall interactions?

Consider using particle body forces (DEFINE_DPM_BODY_FORCE) or simply use wall boundary conditions to account for these electrostatic forces (DEFINE_DPM_BC).

What are the fluid and particle properties? Please tell us more about your setup.
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Old   March 27, 2015, 00:26
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Quote:
Originally Posted by `e` View Post
Interesting topic! What distance (orders of magnitude) are these electrostatic forces acting across? Are you interested in particle-particle or simply particle-wall interactions?

Consider using particle body forces (DEFINE_DPM_BODY_FORCE) or simply use wall boundary conditions to account for these electrostatic forces (DEFINE_DPM_BC).

What are the fluid and particle properties? Please tell us more about your setup.
I'm not sure about the magnitude cause there is no such literature saying that electrostatic force can affect the particle behavior so that it's hard to estimate. I think it's more like combining the particle-particle and particle-wall interactions together since they both significantly give rise to electric charge.
I've checked the particle body force in ANSYS HELP but i cannot find such code solving electrostatic force.
Particles are lactose and fluid is air.
Cheers!
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Old   March 27, 2015, 00:44
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That's right, there's no electrostatic force term built into Fluent's solvers, you'd need to code these yourself with the UDFs.

Have a read of the literature and find some equations you'd like to use for describing the electrostatic interactions and we can code from there.
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Old   June 1, 2016, 19:44
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Quote:
Originally Posted by `e` View Post
That's right, there's no electrostatic force term built into Fluent's solvers, you'd need to code these yourself with the UDFs.

Have a read of the literature and find some equations you'd like to use for describing the electrostatic interactions and we can code from there.
It's been a long time since i raised this question. I finally working on that one. I have found a way to describe the charge transfer between particle and wall.
But i'm just confused that how do i introduce the term of "charge"
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Old   June 1, 2016, 21:51
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What are the equations between the particle and wall you'd like to use? The particle-wall interaction could be modelled by applying a force to the discrete particles.
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Old   June 1, 2016, 22:00
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What are the equations between the particle and wall you'd like to use? The particle-wall interaction could be modelled by applying a force to the discrete particles.
Equations are:
V=Vc-V'=Vw-Vp-V'
where V is the total potential difference between wall and particle. V' is the induced potential difference.
Charge transfer can be expressed as:
Q=k*s*V
where k is the charging constant and s is the maximum contact area.

My idea is to give the particle initial charge as 0 and charge will be transferred while each collision. The accumulated charge would then affect the electrostatic force which consequently affect the bounce/stick behavior.

I can now determine the charge, but i'm confused in how to determine the electrostatic force and how does this force affect the restitution coefficient etc.
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