Learning Forum

[Jabaly]

Dear All 

I'm trying to apply a multiphase model (mixture model) on an ejector ( as a steam jet pump). so I am trying to validate a paper about this topic. where, 
1.The primary fluid (water) with flow rate Q0 and high-pressure P0 is accelerated through nozzle and obtained subsonic speed results in a low-pressure PS (vacuum) at the outlet section of the nozzle.
2.The secondary fluid (air, with flow rate QS) is entrained and accelerated into the mixing chamber.

 

Note#1: 
Paper title: Numerical study on mixing flow behavior in gas-liquid ejector
https://doi.org/10.1007/s42757-020-0069-z 

I applied all Bc's from that paper, Which are: 

1.Mixture model –noslip velocity –implicit-without phase interactions
2.Steady state
3.axi-symmetric
4.Air-water (mixture)
5.K-e model (turbulence)
6.V water =3m/s …………..nozzle
7.V air=3m/s  …………….domain
8.Outlet= atm pressure
9.Methods= coupled
10.Default properties for materials (water and air)    

The problem is: 
There is a problem with the behavior of water when I get the volume fraction results. as you see in fig (A1 to A5) the water flow like a transient behavior ( 200 iterations is different from 400 iterations and so on). 

Note#2: I applied steady-state, not transient 

I think I need to apply phase interactions between water and air. but I don't know what is good interaction between them that I should apply to get the volume fraction as the paper (figure .

may you help me to solve this problem?

Regards, 

Thanks a lot

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[DrAmine]

As we cannot read any paper can you please double check your boundary conditions? Are they accounting for any other thing like mass transfer from water to water-vapor in air? Moreover from your picture there is clear stratification from the other pictures a sort of diffusion which tells me that diffusion force is missing in your case.

[Rob]

Please also post the velocity field at 1200 iterations. 

[Jabaly]

Thanks for your reply.

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plz see attached link (pdf file), this is a presentation about that paper. It will give us a good and quick view of the ejector.

The link:
https://drive.google.com/file/d/1mdSTm3Zi1Kol20Ib0K3u_EXg0n6BxXAf/view?usp=sharing

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and yes you are right, the flow looks like stratified flow in my result, and I need to apply something like ( evaporating -condensation interaction) or ( cavitation) , I should reach to bubble flow as the paper. 
but you know, evaporating -condensation interaction can be used when you have one fluid like water, and then convert liquid to vapor. 

but in our system we have air-water mixture, so what is the interaction that I can apply in fluent ?! 

Note#1: the paper does not mention anything about the interaction between water and air. 
Note#2: you can see the velocity and pressure  counters, also velocity profiles 

[Jabaly]

Thanks for your reply.

yes sure, plz see attached photo for the velocity contours and profiles, and this link (pdf file), this is a presentation about that paper. It will give us a good and quick view of the ejector. also, you will find the velocity profile in slide #17. 

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The link:
https://drive.google.com/file/d/1mdSTm3Zi1Kol20Ib0K3u_EXg0n6BxXAf/view?usp=sharing