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Old   August 8, 2013, 08:22
Default Question about Relative Velocity
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Ding Chao
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Hi,everyone
I am modeling a bubble flow useing CFX,and I need use relative velocity in CCL. I find that the slip velocity have no unit in the CFX reference_Guide,and I don't know this is why.Could anyone explain to me the question?
Could I use this expression to calculate the relative velocity?
Vr=sqrt((air.Velocity u-water.Velocity u)^2+(air.Velocity v-water.Velocity v)^2+(air.Velocity w-water.Velocity w)^2)
If anyone know the answer,please help me!
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Old   August 8, 2013, 18:58
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Glenn Horrocks
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Seems strange. I would have thought slip velocity would be in m/s. Also make sure you are using the correct variable. There is "Slip Velocity" for ASM models, "particle Slip velocity" for particles, "Slip Velocity Magnitude".

There should be no need to calculate this, it should already be a variable in the solver. You just have to find the right variable name.
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Old   August 8, 2013, 21:10
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Quote:
Originally Posted by ghorrocks View Post
Seems strange. I would have thought slip velocity would be in m/s. Also make sure you are using the correct variable. There is "Slip Velocity" for ASM models, "particle Slip velocity" for particles, "Slip Velocity Magnitude".

There should be no need to calculate this, it should already be a variable in the solver. You just have to find the right variable name.
Thank you for your reply,but I don't understand what does the "Velocity of an algebraic slip component to the continuous" mean.Why it have no unit? What does the algebraic mean?
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Old   August 8, 2013, 22:11
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I don't understand it either. It might be a documentation mistake. Also we might be misunderstanding the variable. I am not sure which is the case.
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Old   August 8, 2013, 23:02
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Originally Posted by ghorrocks View Post
I don't understand it either. It might be a documentation mistake. Also we might be misunderstanding the variable. I am not sure which is the case.
Thank you all the same!what do you think that if I use" Vr=sqrt((air.Velocity u-water.Velocity u)^2+(air.Velocity v-water.Velocity v)^2+(air.Velocity w-water.Velocity w)^2)"to calculate the relative velocity between gas and liquid?Is it accurate?
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Old   August 8, 2013, 23:26
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I suspect the value you get from your equation should be the same as Slip Velocity Magnitude, providing you are doing an ASM model. Is it the same?
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