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Is it possible to find the droplet size (SMD) of an atomizer as an output of simulati

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Old   December 30, 2018, 13:58
Default Is it possible to find the droplet size (SMD) of an atomizer as an output of simulati
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CFX requires Droplet size as an input to simulate atomizers or spray. It also requires other spray properties line cone angle as input!

In a case where all these parameters are unknown for a given design, is it possible to find it by simulation?
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Old   December 31, 2018, 05:58
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When using Lagrangian particle tracking, it is possible to use models to include breakup, collision, evapration, etc. In that case, it is possible to predict the droplet diameters. However, the starting diameter and initial cone angle remain as input parameter.

When using Eulerian multiphase modelling, it is possible to calculate the liquid layer inside a nozzle, droplet forming, cone angles, etc., starting from a continuous phase But You need a huge computer and patience, since you require very fine mesh, and extremely small timesteps to capture surface tension effects. Not really feasible.
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Old   January 3, 2019, 08:14
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Thanks for the reply Gert-Jan.
Is it a okay to assume that the inlet drop diameter is equivalent to the exit diameter of the orifice or injector?
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Old   January 3, 2019, 17:49
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In general no. It depends a lot on the type of nozzle, orifice diameter, geometry, pressure drop, rheology, viscosity, break-up and coalesensce process, etc. Too many parameters determine the droplet size.
Mostly you take a nozzle, perform measurements on droplet size at certain distance from the nozzle and use that as input for a lagrangian particle tracking.
If you don't want to do measurements, you have to do Eulerian calcualtions, but that is a hell of a job.
Alternatively, rely on specifications of the nozzle supplier, if you use one from the shelf.
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