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-   -   HELP!!TWO PHASES FLOW (http://www.cfd-online.com/Forums/cfx/18584-help-two-phases-flow.html)

dingding July 18, 2001 20:49

HELP!!TWO PHASES FLOW
 
Hi,everyone!

I am simulating the oil-water two phases flow. I set two inlets at LOW I of a block, one is oil water inlet and another is water inlet.

I use the homogeneous model to simulate the free surface between the oil and the water. The problem is that U, V, MASS and VOLUME FRACTION of each phases don't convergence, in addition, no free surface in the CFX-analyse, why? I used a single water compuation as the START dump file, but no free surface being found!

Please help me! Thanks in advance.


De-Wei Yin July 19, 2001 23:52

Re: HELP!!TWO PHASES FLOW
 
Check the initial guess. If you don't specify the initial phase distribution, the solver defaults to 50% oil and 50% water. See CFX-4 Solver Reference Example 29 (provided with the software).

dingding July 20, 2001 00:45

Re: HELP!!TWO PHASES FLOW
 
hi, all

I have set two inlet.

One inlet is oil , oil velocity is 0.01m/s and volume fraction is 1.0. At oil inlet, water velocity is 0 and volume fraction is 0.0.

Another inlet is water, water velocity is 0.01m/s and volume fraction is 1.0. At water inlet, oil velocity is 0 and volume fraction is 0.0.

I use the laminar model to simulate this transient flow, but there are the same problem.

please help me!

Jon July 20, 2001 04:31

Re: HELP!!TWO PHASES FLOW
 
Hello,

I would set the inlets as both the phases having the same velocity, but different volume fractions.

How have you set up your fluids? Let me know what kind of problem you are trying to simulate (i.e. free-surface, disperesed particles) and then tell me how you have set up the fluids (continous/dispersed) and which multi-phase models you are using.

Also, the initial conditions will be important w.r.t. the type of simulation you are perfroming and the 'true' physical initial conditions.

Jon

Fred August 6, 2001 03:59

Re: HELP!!TWO PHASES FLOW
 
Hello

I agree with Jon's answer.

You have to put the same speed for the two components but different volume fraction ->inlet_oil : oil_speed=0.01 / oil_vf =1

water_speed=0.01 / water_vf=0 ->inlet_water :oil_speed=0.01 / oil_vf =0

water_speed=0.01 / water_vf=1

If you are using a transient simulation, and using a restart with a dump file, the command "initial guess" overwrites all the existing field.

Excuse me for my poor english.

Regards,

Fred


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