Learning Forum

[Srikar V.S]

Hello, I'm a student who is relatively new to ANSYS Fluent. 

I apologize i advance for this big of a post, but i urge you to please read through patiently and help me with this problem.

My project involves simulation of a mixture of fish feed (which is kind of like sand) and water in a small cylindrical pipe which is going through a die. Now I thought of doing the 2D analysis for it, sort of approximately, to see how such kind of an analysis is done. 

The actual process is such that fish feed particles are constantly fed through a hopper into a housing pipe. Water is also added manually through the same - but just added at first and left like that - it is not continuous supply. There is a lead screw which is taking the whole mixture forward. The mixture is like pasty now (kind of like how when we mix water with sand it becomes mud). This mud like substance travels throughout the pipe now and comes out through small holes of a die.   

I want to simulate this. But first i thought let me just try to simulate this mixture properly then i will look at the hopper and all other stuff.

According to whatever amount of research i have done, these are the models i took for analysis: 

1. Multiphase Eulerian flow with Dense Discrete Phase model 
2. Transient analysis
3. Primary phase - water
4. Secondary phase - fish meal  - Granular with gidaspow model for viscosity and lun et-al model for solid pressure and remaining everything is default. 
5. Cell zone conditions - Mixture
6. Boundary conditions - inlet - velocity inlet, outlet - pressure outlet, walls are no slip
7. Injection of discrete phase is taken at the same place as inlet with the same velocity
8. Methods of solving - PC SIMPLE, Pressure - PRESTO!, Momentum and allothers are first order upwind schemes
9. Lastly, Hybrid initialization with 1000 iterations and a suitable time step. 

Problem here is, the secondary phase is infact more in quantity than the primary phase (water). I also do not know how to correctly give the injection of discrete phase or if even that is the right way to do for my problem. 

Im not able to get the desired solutions with these settings no matter what, so i ask you to help me put with this. I have attached all the pics related to the analysis below. 
Please point if there is anything wrong with these/ Suggest me with the most suitable model for such an analysis. 

Regards, 

Srikar.V.S.

[Rob]

If the solid volume fraction is high enough to get a slurry I'd not recommend DDPM, standard Eulerian will (probably) be better. However, depending on what you want to see you may find the slurry mixture can be modelled using a nonNewtonian viscosity. 

Try running the model with just water to start with, it should be OK steady state and you'll learn how the solver works. Then make it more complicated. 

[Srikar V.S]

Thank you for the reply!
I will try that.