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#21 |
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Do you have an idea how to set up a good expression for this? I thought about something like a half of a circle and set the velocity as normal (perpendicular) on the function. But it seems to be quite difficult, doesn't it?
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#22 |
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Glenn Horrocks
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If you are using lagrangian particle tracking CFX has several built in models to generate various spray shapes, such as conical. As this model is used to model IC engine fuel injectors it covers typical fuel injector spray shapes quite well. So it is quite easy to do.
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#23 | |
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Quote:
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#24 |
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Glenn Horrocks
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If the spray centreline is on y=0 and the spray extends from -1[mm] to 1[mm], then if you set the:
U Velocity to the spray velocity V velocity = y/1[mm]*10[m/s] W Velocity = 0 Then the spray will do a 2 dimensional fan from -10[m/s] to +10[m/s]. But I don't understand why you would want to do this as a Eularian model cannot model spray breakup which appears to be the point of this analysis. Your only option is a Lagrangian model and that is set up completely differently.
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#25 |
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Thank you, this looks fine!
Spray breakup isn't point of the analysis anymore. I try something on a different way. |
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#26 |
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Further question:
I have now a suitable result of my spray flow. At the beginning (nozzle outlet) the Volume Fraction is commonly with value 1.0 and to the end of my simulation region it is going to spread and the Volume Fraction is decreasing. I would like to know now, if there is a correlation between Volume Fraction and Drop Distribution. Does somebody know a good way to figure this out? I hardly found any papers focusing on this issue... Thank you in advance for your answers! |
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#27 |
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Glenn Horrocks
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What do you mean "drop distribution"? If you mean drop size distribution - then if you are doing a normal Eularian simulation like you mentioned before, then the drop size is defined in the model setup, so the drops will be the size you defined them to be. If you mean drop velocity distribution then just look at the appropriate variable in the post processor.
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#28 |
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Yes, I mean drop size distribution.
What if I setup an multiphase Eulerian model but with two continuous fluids? How can I sort it out then? Did someone find some literature about that before? |
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#29 |
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Glenn Horrocks
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Please have a careful read of the CFX theory documentation on multiphase modelling. You need to know what the models mean, what they do and what they assume before you can make sensible choices about which model to use. So you really should be answering that question yourself if you are doing this sort of work.
Eularian models are not generally used to have varying drop size. Lagrangian models are more commonly used for this. There are some Eularian models which cover variable drop size (eg MUSIG) - you might want to investigate these models. I am no expert on MUSIG, but I suspect MUSIG is not going to be appropriate. Then you are forced back to Lagrangian models again ![]()
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Tags |
ansys, breakup, cfx, multiphase, spray |
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