two phase air-water vertical pipe

hasan-hasani · March 23, 2009, 07:02

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

zhaopeng · March 23, 2009, 13:07

the work I do is similar to yours.I think it is better to set air inlet to mass flow inlet.

hasan-hasani · March 25, 2009, 03:51

Quote:

Originally Posted by zhaopeng

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

zhaopeng · March 25, 2009, 04:53

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]

March 23, 2009, 07:02	two phase air-water vertical pipe	#1
hasan-hasani New Member mohammad hassan Join Date: Mar 2009 Posts: 2 Rep Power: 0	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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March 23, 2009, 13:07		#2
zhaopeng Member zhao peng Join Date: Mar 2009 Posts: 41 Rep Power: 17	the work I do is similar to yours.I think it is better to set air inlet to mass flow inlet.

March 25, 2009, 04:53		#4
zhaopeng Member zhao peng Join Date: Mar 2009 Posts: 41 Rep Power: 17	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]