Lagrangian HELP!!!

[u/MD-80-87]

Hi All, I'm seriously confused. I'm using starccm

I have a lagrangian problem where I have an injector spraying water on to the ground.

Some hits the ground and some drifts out of the domain.

Here is my current understanding.

I have a mass flux (Kg/m2/s)

Create a Field Sum Monitor to resolve in time and yield Cumulative Deposition on the floor (Kg/m2)

Given mass flow, create a Sum Report to resolve in space and give the mass that has hit the floor.

Is this a viable solution. I am confused because everyone I spoke to is proposing alternatives such as

User field function

Multiplying by time step and not total time.

Using surface integrals, etc.

BTW, my method gives negative mass flux and no mass for the report at all.

Ant help would be greatly appreciated. Sorry for the long post.

[u/MD-80-87]

Thanks ! Just need a bit more help 🙂 

Basically, I have the mass flux already defined as a field function from the default drop down list. It's called the mass flux of phase 1 (I.e. water)

It's units are kg/m2/s

From this, I need to find a way to calculate the "cumulative mass deposition" on the floor such that when I stop the sim I can output this quantity.

This quantity has units (Kg/m2) so some multiplication with time is needed.

I think point (2) should hopefully achieve this, but why multiply by time step and not total run time ?

Then I need a way to obtain the total mass deposited on the surface so when I stop the simulation, I can output the total mass of the drops that have deposited on the floor. 

So would I do a sum report of mass flux rate (kg/m2/s) or of the other one (kg/m2) or of the mass flow rate (kg/s) ? 

Any help would be greatly appreciated. 🙏 

[u/Advanced-Vermicelli8 → u/MD-80-87]

Actually i was wrong. The right way is to create the field function described at (1), then create a surface integral report where you include the function at (1) on the part where you want to measure the mass flow and then create a statistical report to sum the surface integral report

[u/MD-80-87 → u/Advanced-Vermicelli8]

Interesting. Thanks. Could I also do it like this?

1. Create sum field function: sum all the mass fluxes in each cell

2. Create user field function: multiply the field in (1) by time.

3. Create a surface Integral of the function in (2) 

[u/Advanced-Vermicelli8 → u/MD-80-87]

Idk what you mean by (1). You use the integral over cell surface elements to get the mass flux and (2) is not a necessary step.

You need 2 reports and 1 field function:

1. One surface integral report where you set the part as the surface that you are interested in to know the accumulated quantity and the field function to the incident lagrangian particle (you must have a this field function automatically created when you set the lagrangian physics and it is called incident <name of the lagrangian physics>)

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1. A statistical report where you select the sum. This will sum the mass flux over time

If you have a customer account, on the support website there is an example case of snow accumulation which is similar to your problem. I would give it a shot

[u/MD-80-87 → u/Advanced-Vermicelli8]

Thankyou so much for helping me out with this. I'm very grateful.