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-   -   How to choose the mean diameter value for dispersed fluid? (http://www.cfd-online.com/Forums/cfx/93897-how-choose-mean-diameter-value-dispersed-fluid.html)

creddy_trddc October 30, 2011 02:27

How to choose the mean diameter value for dispersed fluid?
 
Hi everyone,

I am simulating two-phase flow consisting of one continuous phase and one dispersed fluid phase (Here Argon gas is injected into a vessel consisting of molten steel from nozzle located at bottom).

Here I am considering Argon gas as dispersed fluid and molten steel as continuous phase.

In CFX-Pre under Fluid details tab it was asking for mean diameter of dispersed fluid (Argon gas),

Can any one please tell me how to choose the value of mean diameter of dispersed fluid.


In CFX manual it has mentioned "Mean Diameter
For a Dispersed Solid or Dispersed Fluid, you must supply the mean
diameter of the dispersed particles, droplets or bubbles constituting the
phase. The mean diameter is the actual diameter for spherical
particles. For non-spherical particles, you should provide the Sauter
mean diameter, that is, the diameter of a sphere possessing the same
volume as the particles."

But I am not getting how to choose the right value for mean diameter.



FLUID: Argon gas
FLUID MODELS:
FLUID BUOYANCY MODEL:
Option = Density Difference
END
MORPHOLOGY:
Mean Diameter = 0.68 [m]
Option = Dispersed Fluid

END
TURBULENCE MODEL:
Option = Dispersed Phase Zero Equation
END
END
END
FLUID: Molten Steel
FLUID MODELS:
FLUID BUOYANCY MODEL:
Option = Density Difference
END
MORPHOLOGY:
Option = Continuous Fluid

END


Looking forward for reply.


Thanks & Regards,
Niranjan Reddy.

ghorrocks October 30, 2011 05:30

The bubble diameter is a function of the flow conditions and therefore you must specify it. Hopefully you know it from experimental results. If not, you can estimate it from the argon nozzle diameter and look in the literature for gas bubble size from a nozzle.


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