Discussion Forum

Hi, for the particle mass (or diameter) you could type something like:

1E-6+2E-7*random(particleindex)

This means the particle mass will range from 9E-7 to 1.1E-6 uniformly.

The function random(particleindex) generates a uniformly distributed random number for each particle between -0.5 and 0.5.

Aha, Thanks a lot. Acturally I asked for a collegue of mine. Hopefully he will tried it out.

Yuexia

Hi,
Is there any similar way to simulate only two types of particles? How can I specify the function?
Thanks

I am looking at doing a simulation with salt water (sodium and chlorine ions). So, this would be quite useful for me. Similar to what Daniel Smith said, I would think if you were to use an "IF" statement you could get essentially the same effect.

1E-6+IF(random(particleindex)<0.5,0,2E-7)

Perhaps this would give you half of your particles at 1 µg and half at 1.2 µg. Although, I have yet to try this. For my case, I think I would need to do that for my sodium and chlorine ion masses but also for the charge of each particle being

IF(random(particleindex)<0.5,1,-1)

Question on this, what if I wanted to associate particle masses with charges found in the previous random number generator? Is it possible to just assign certain particle indexes to specific properties? Say, with 1000 particles,

m = IF(particleindex<500,35.453/N_A_const,22.98976/N_A_const) where N_A_const is a physical constant in COMSOL for avogadro's number

and

Z = IF(particleindex<500,-1,1) for the charge of the same respective ions

Someone (Daniel Smith perhaps) please let me know if there is flawed logic here.

It would appear you can do this with

mp = 35.453[kg/mol]/N_A_const-mod(fpt.pidx,2)*12.46324[kg/mol]/N_A_const
Z = -1+2*mod(fpt.pidx,2)

where the mod(fpt.pidx,2) picks every other particle. This was needed because of the placement of particles by particle number. It placed all low number particles in the center of my release circle, this method gives me an even distribution of Na+ and Cl- ions.

The numbers needed to be added for this style of function to work, but it basically gives me properly assigned particle masses and charges for sodium and chlorine ions in the water. Now to get the magnetics to work with it.

Hi Brockap3
I am trying to simulate NaCl ions moving in a variable electric field. Could you let me know how you did the implementation in your model. I am very new to Comsol by the way!
Thanks
Juan

Sorry for the delay. I have made no progress on this issue. I will be watching a TechBriefs/COMSOL webinar on Thursday the 22nd about this hoping for more insight. I am hoping to look into this is the very near future.

--
~Brock

Hi. I just came across this thread, and I thought I'd mention another way to add more than one type of particles to a simulation. In the Particle Tracing node, an "Override Properties" feature can be added. The properties of the particle are defined in the "Override Properties" settings. Then, this new type of particle can be assigned to a "Release" feature by selecting "Override Properties" in the "Inherit Properties" setting. Just add an "Override Properties" and a "Release" feature for each type of particle you want to add. I hope this helps.

Dear David

your approach works fine. Thanks!

Would it also be possible to extend your suggestion assuming that my function follows a probability density function: f(x;mu;sigma) = (1/sigma*root(2*pi))*e^-0.5*(x-mu/sigma)^2?

The normal distribution is parametrized in terms of the mean and the variance, denoted by mu and sigma, respectively.

I know my mu and sigma. I am also expecting my particle size ranging from 1 µm to 100 µm.

Thanking you guys in advance!

Nevaf

Hi,

I need to do simulation for multiple ( 4 particles) spherical particles with different length, frequency and permeability. Could you please tell me how can I do the geometry and define the Infinite element domain and the particle domain.

I am new with COMSOL.

Thanks in Advance.

Nazu

Where to insert this expression?

I was actually inserting in charged particle tracing module in comsol

Hello,

I have the need to know the mass of the particles that reach a boundary in my simulation.
How can this condition be set.

Thanks

How can we introduces particles with a given particle size distribution in particle tracing module? If for example a normal distribution based on number or mass?