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two phase air-water vertical pipe

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Old   March 23, 2009, 07:02
Default two phase air-water vertical pipe
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mohammad hassan
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hi all
my problem is a 2m long vertical pipe with 5cm diameter that air injected from a 2.5mm hole bellow the pipe and boundry condition is pressure inlet for water and velocity inlet for air with 1 m/s and pressure outlet for mix at top of the pipe i used eulerian model and unsteady with k-e model for turbulance and bubble diameter of 3 mm.but i cant reach convergency.pleas help me. i need your help soon
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Old   March 23, 2009, 13:07
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zhao peng
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the work I do is similar to yours.I think it is better to set air inlet to mass flow inlet.
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Old   March 25, 2009, 03:51
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Quote:
Originally Posted by zhaopeng View Post
the work I do is similar to yours.I think it is better to set air inlet to mass flow inlet.
hi
i think velocity inlet for compressible flow is good and mass flow for incompressible flow
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Old   March 25, 2009, 04:53
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Velocity inlet boundary condition is intended for incompressible flows, and its use in compressible flows will lead to a nonphysical result because it allows stagnation conditions to float to any level. You should also be careful not to place a velocity inlet too close to a solid obstruction, since this could cause the inflow stagnation properties to become highly non-uniform. [FLUENT 6.3 User's Guide 7.4]

Mass flow inlet boundary conditions are used in compressible flows to prescribe a mass flow rate at an inlet. It is not necessary to use mass flow inlets in incompressible flows because when density is constant, velocity inlet boundary conditions will fix the mass flow. [FLUENT 6.3 User's Guide 7.2.1]
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