How to simulate a simple fan inside a room ?
 

Hi
i want to simulate a fan inside a room to simply flow the air from its backside to its front side .
to flow the air from and into the room.
knowing its mass flow rate Kg/s
and Air velocity m/s

without involved in the details of simulating its blades or modeling its internal details.

can I simulate it as subdomain or interface or what ... and how?

thanx for your time and help.

Either define a volume and apply a momentum source to it, or define an interface and apply a momentum source on that.

problems in the momentum source
 

i want to simulate a jet fan of diameter 0.3 m and length on 2 m
velocity of 18 m/s
mass flow rate of 1.2 m^3/s

when i input the momentum source as momentum per volume
( Mass flow rate * velovity /Volume ) in the direction of the flow axis

the results are not realistic

please advice me with the way of input a momentum source

thnx for help

An alternative approach is to make the inlet of the fan an outlet in your domain and the outlet of the fan an inlet. You can specify the mass flow rate easily that way.

need to move air inside the room
 

thanx for reply

but i need the jet fan to move the smoke inside the room
so i need to flow the poluted air inside the room

i need to know the exact setup of the momentum source of the subdomain (the fan)

i have non realastic solution

when i use general momentum source as :

x component = 0 kg m^-2 s^-2
y component = (Mass flow rate * velocity of air from the fan / volume of
the fan) = 150 kg m^-2 s^-2
z component = 0 kg m^-2 s^-2

and

x component = 0 kg m^-2 s^-2
y component = C *(Mass flow rate * velocity of air from the fan / volume
of the fan) = 15000000 kg m^-2 s^-2
z component = 0 kg m^-2 s^-2

with momentum source coff of 100000 kg m^-3 s^-1

and both

give me non realastic solution with wrong velocities and pressures

thnk u for your help and time

You are not taking into account the momentum of the incoming air. You need to change the velocity component to something like (VF-v) where VF is the velocity of air you want (18m/s) and v is the local control volume velocity in the appropriate direction. This way the source term goes to zero as the velocity of the air approaches the velocity you want.

And you will almost certainly need the mom source coefficient, so use that approach.

local control volume velocity
 

thnx very much for reply

but can i know more information about knowing the (local control volume velocity) meaning

and how to know and input it

and if i correctly understand that the momentum source term is equal to [MassFR*(VF-v)/ Volume]

or am i wrong

thnx for help

Yes that is correct. But you have to make sure the sign of the velocity component is correct, so you might need to change the sign, but that is the general idea.