mass flow in point injection
 

Does anyone know how do i calculate the mass flow in file injection in FLUENT, or do i just ignore it and just set as 1 cause the density is constant and it's just 1 particle.
((x y z u v w diameter temperature mass-flow) name )

I don't know what you mean with 'calculate'. You are the one who defines the mass flow rate. If you want the particle stream to represent 1 kg/s, you put 1. If you want the particle stream to represent 0.000001 kg/s, you put 0.000001.

The 'mass flow rate' does not affect the trajectory calculation at all, merely the post-processing. (Maybe except when you do a coupled simulation?)

What the calculate mean is , are there any formulas determining this value if I don't know it. Cause there's just one particle injecting in that point, velocity and mass are constant, I'm just wondering that does it affect the result and the answer you said is No. So do I just give it a random number or just leave the word "mass flow" there?
Cheers!

If you apply a isothermal boundary condition, which temperature do you have to take? Is there a formula to determine this value? No. If the problem you are trying to solve has a temperature of 300 K at that boundary, 300 K, put 300 K in, and if you the boundary is 200 K, put 200 K in.

Similarly here: there is no formula to calculate the mass flow rate, because you have to choose the mass flow rate. If your problem has 1e-9 kg/s particles coming in, put the value 1e-9 there.

I understand your problem, though: you don't want to have a 'stream' of particles, but just want to have one particle. Say for simplicity that your particle is 1 milligram (1e-6 kg), how often is it injected? One time per second, then it would be 1e-6 kg/s. One time per 1000 seconds, then it would be 1e-9 kg/s. But in your case it is just once, so which value to put in?

The answer: it does not matter. If you put the value 1e-6 kg/s in, if Fluent needs to know (for postprocessing purposes) the amount of particles injected per second, it will use 1 per second. If you put the value 1e-3 kg/s in, fluent will imagine 1000 particles were injected per second. And if you never do any postprocessing in which Fluent needs to know the number of particles injected per second, the value is never used. You are very very very likely in this last situation, so you can just put the value 1 in. It is probably not good to keep the words "mass flow" there, since Fluent expects a number and might get confused, but I am not sure of that.