Learning Forum

[prebenjs]

Hi,

I'm having trouble setting the diameter of the secondary phase (default =1e-05 m) for a system of air and water in a t-junction where water is the secondary phase, in a laminar flow. Can anybody provide me with some guidance on how to determine this?

Also i wonder when "Interfacial area concentration" should be used. Didn't quite grasp what was meant in the theory and user guide.

[Rob]

Unless you have phase transfer leave it alone for now. knows more about the theory, but default should be OK for what you're doing.
Regarding the droplet diameter, some information is here https://forum.ansys.com/discussion/35701/diameter-secondary-phase and it comes down to what is going on in the system and how big the pipe/domain is.

[prebenjs]

My concern is that if i use a pipe which is smaller than the default value, what would happen then? Should i adjust the diameter to the pipe-size then?

[DrAmine]

It affects the drag and momentum so it is a mean to influence that coupling between the phases.

[prebenjs]

Do you have any suggestions to literature to set this parameter?

[DrAmine]

No but you might look after some publication on slug flows where a symmetric model is used and the diameter is something you interpret as "what if a droplet get separated.. or bubble get entrained" or just as numerical parameter to affect drag and IAC. Also check the AIAD publications which is based on Eulerian Multiphase Approaches and where the drag is based on blending between Continuous and dispersed morphologies (as well as IAC)

[prebenjs]

Just a quick question. Does the diameter only influence the drag and momentum in e.g. droplets that are made ? or does it also influence the drag and momentum in the continuous phase before a droplet is formed?

[DrAmine]

No droplets / no interfacial area-> No effects.

[prebenjs]

Okay so if i understand correct the diameter one sets only affect the drag and momentum of e.g. a droplet. But it does not affect the how large droplets are made and how fast geometries / how fast these are made ?
So in the case of having two continuous phases, and expecting droplet to be formed. If these droplets do not possess any values of interest (only focusing on the two continuous phases and pressure of these (also pressure drop after detachment)), does this mean that one can only use the default diameter (although maybe not representing the droplet in a good way) ?