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-   -   How to define a mass source at a velocity inlet ? (https://www.cfd-online.com/Forums/fluent/72696-how-define-mass-source-velocity-inlet.html)

 cfdiscool February 15, 2010 11:26

How to define a mass source at a velocity inlet ?

Hallo all

I am trying to define a mass source where the high pressure water should be supplied, this is thorough nozzle, I defined the nozzle volume(int) as fluid and now when i turn on the mass source term I see that i have to define the mass source per unit volume

units are kg/m^3-s

what is this unit volume ? i have a numerical value of mass flow rate at the inlet of this nozzle which i have in kg/s... what is the unit volume in this case ...a cell or entire volume of the nozzle...

thanks:)

 CFDtoy February 17, 2010 11:57

mass source

Code is Finite Volume My friend. so, define, mass per volume please. Basically, we do

d(rho)/dt*Vol(cell) + sum (flux) = Source *volume (cell)

Before solving the problem, volume is multiplied to the entire eqn in the Finite Volume method.

You provide per volume and it will compute the source appropriately.

btw, if it asks for per volume, it is the cell volume not the nozzle.

Hope this helps.

/CFDtoy

Quote:
 Originally Posted by cfdiscool (Post 246087) Hallo all I am trying to define a mass source where the high pressure water should be supplied, this is thorough nozzle, I defined the nozzle volume(int) as fluid and now when i turn on the mass source term I see that i have to define the mass source per unit volume units are kg/m^3-s what is this unit volume ? i have a numerical value of mass flow rate at the inlet of this nozzle which i have in kg/s... what is the unit volume in this case ...a cell or entire volume of the nozzle... any suggestions please??? thanks:)

 cfdiscool February 17, 2010 12:22

After a long and long head scratching i found out the fact behind this unit system....

answer to my question can be as follows:

the mass source per definition in FLUENT is per unit volume...

so mass source has units as kg/s in SI units , since all sources are to be assigned in SI units
The units of "unit volume" is m^3.

This "unit volume" can be a single cell where the source lies or a fluid domain which acts as your source.

simply to input the value of mass source one needs to do following

(mass flow rate)
-------------------------------- units are (kg/s)/m^3
(volume of the source)

volume of the source = (surface are of the source zone)*(height of the source zone)

please correct if am wrong

wishes

 KOX September 4, 2011 11:59

answer + another question

Hi there

I think you interprete corectly how the mass source works. I think the same.
However could you tell me please if this mass source works in your model, whatever you were trying to simulate? In my case even if I set some certain value (kg/(m^3*s)) the mass sourc doesnt work. There is nothing released from the source even if I add additional momentum source.