when use Interaction with Continuous Phase?

asal · August 14, 2013, 11:57

Hello everybody.

I want to know until which particle sizes, ones can neglect the effect of particles over the flow field? or in another say until what particle sizes we can exclude the effects of the discrete phase trajectories on the continuous phase?
It is well known that if the particles are to small, then they don't affect the flow field and then it is not needed to enable "Interaction with Continuous Phase". But I want to know the size, if we assume that particles have water properties.
I am appreciate if some one can offer me any article regarding this.
thanks.

John · August 14, 2013, 14:44

Quote:

Originally Posted by asal

Hello everybody.

I want to know until which particle sizes, ones can neglect the effect of particles over the flow field? or in another say until what particle sizes we can exclude the effects of the discrete phase trajectories on the continuous phase?
It is well known that if the particles are to small, then they don't affect the flow field and then it is not needed to enable "Interaction with Continuous Phase". But I want to know the size, if we assume that particles have water properties.
I am appreciate if some one can offer me any article regarding this.
thanks.

This is related to particle stokes number. http://en.wikipedia.org/wiki/Stokes_number

You can neglect the effect of particles over the flow field when Stokes number is far less than 1.

asal · August 16, 2013, 09:03

Hello!
well, thanks for your helpful reply.
As it is clear, the Stokes number is defined as:

$Stk = \frac{\rho_{d} d_{d}^{2} U_{\infty}}{18\mu_{g} L}$

$\rho_{d}$ and $d_{d}$ are the particle density and diameter, $\mu_{g}$ is the dynamic viscosity,

is a characteristic dimension of the obstruction and $U_{\infty}$ is the bulk velocity.

I want to calculate the Stokes number in a room, that particles are liberated from the people exist within the room. The inlet was placed at the ceiling level and outlet on the vertical walls. In this case which values should be assigned to

and $U_{\infty}$ ?
I cannot understand what should be considered as obstruction. for the bulk velocity, should I assign the inlet velocity, average velocity in the room, or what?

thanks.

August 14, 2013, 11:57	when use Interaction with Continuous Phase?	#1
asal Senior Member Astio Lamar Join Date: May 2012 Location: Pipe Posts: 186 Rep Power: 14	Hello everybody. I want to know until which particle sizes, ones can neglect the effect of particles over the flow field? or in another say until what particle sizes we can exclude the effects of the discrete phase trajectories on the continuous phase? It is well known that if the particles are to small, then they don't affect the flow field and then it is not needed to enable "Interaction with Continuous Phase". But I want to know the size, if we assume that particles have water properties. I am appreciate if some one can offer me any article regarding this. thanks.

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August 16, 2013, 09:03		#3
asal Senior Member Astio Lamar Join Date: May 2012 Location: Pipe Posts: 186 Rep Power: 14	Hello! well, thanks for your helpful reply. As it is clear, the Stokes number is defined as: $Stk = \frac{\rho_{d} d_{d}^{2} U_{\infty}}{18\mu_{g} L}$ $\rho_{d}$ and $d_{d}$ are the particle density and diameter, $\mu_{g}$ is the dynamic viscosity, is a characteristic dimension of the obstruction and $U_{\infty}$ is the bulk velocity. I want to calculate the Stokes number in a room, that particles are liberated from the people exist within the room. The inlet was placed at the ceiling level and outlet on the vertical walls. In this case which values should be assigned to and $U_{\infty}$ ? I cannot understand what should be considered as obstruction. for the bulk velocity, should I assign the inlet velocity, average velocity in the room, or what? thanks.