Learning Forum

[ayoub elou]

I want to simulate the flow of sediment-laden water in a lamella decanter using the Euler-Lagrange approach, but I don't know how to enable this approach in ANSYS Fluent. can'you help me and thanks

[ayoub elou]

Can I activate it from : models --multiphase-----eulerien and actived the dense discret phase 

or i active dense discret phase withowt actived the multiphase ?

 

[Rob]

DDPM may not be entirely suitable. I suspect Eulerian-granular is going to work best for sedimentation. If you're looking at separation DPM may work well. It depends on what you're trying to find out from the model. You also need to understand what each model does: in multiphase we often choose the model based on the desired results: ie what we want to show/know from the simulation. 

[ayoub elou]

thank you Dr Rob 

In my simulation, I want to show where the particles settle in the basin and also the flow velocities in the sedimentation basin to address the issue of sludge resuspension. i m used the discret phase model DPM zhitout actived the eulerien in lultiphase model it's good or not  for this simulation ?n

 

 

[ayoub elou]

this the steps of my simulation 

1)in the general step ; i'm used transiet time + garvity + prssure-velocity 

2) model: i on the discret phase(create injection) + k-epsilon RNG 

materiel: water-liquide continuos phase+ particule 

cell zone condition: water

and bondery condition 

initailisation 

run calculation 

 

[Rob]

Messy, given sludge is only just about multiphase. Eulerian or mixture is one option, possibly the best one without getting too complicated. 

[ayoub elou]

can you help me to get the step of this simulation in ansys?n 

[Rob]

Turn on Fluent, click on Help, read the documentation on the multiphase models. Then do the multiphase tutorials, also in Help. Check AIS (Learning on here) for materials. Come back with specific questions about anything you're not sure about. 

[ayoub elou]

i read the help in ansys , l have 2 questions :

1) can i use the discret phase modele or the eulerien model and actived the discret phase? 

2) how i can initialise the bassin is empty at t=0

 

[ayoub elou]

[Rob]

Yes. But note the limitiations/requirements of each approach. 

Define "empty". Empty of water, particles or both? 

[ayoub elou]

empty for 2 phases 

 

 

 

[ayoub elou]

[ayoub elou]

this image is the contor of velocity after 10s.

i don't know if the basin is filled with water before starting the calculation? How can we determine the initial state of the basin before starting the calculation?.

[ayoub elou]

[ayoub elou]

[Rob]

If you're running with an empty domain you'll need another phase, ie air.  

[ayoub elou]

Indeed, the calculations will be quite complex with three phases (water+air+particles). Therefore, I would like to initialize the sedimentation tank as being filled with water at t=0. However, I am uncertain about the method to achieve this. How can I accomplish this initialization?n

[Rob]

You need to specify the initial conditions, do not just rely on Hybrid. It'll be covered in the multiphase tutorials available in Help. 

[ayoub elou]

But when I work solely with the discrete phase model, in the standard initialization, it doesn't provide me with the option to input the volume fraction; it only includes velocity, pressure, and turbulence parameters.n

[Rob]

Yes, that's correct. Are you now working with DPM or Eulerian? 

[ayoub elou]

i worke whit DPM model 

[Rob]

In that case why wouldn't the volume be full of water? Did you read up on the DPM model assumptions? 

 

[ayoub elou]

Yes, of course, I have seen all the assumptions and mathematical equations of this model. My question is, how can I determine that my settling tank is filled with water at t=0?n

 

[ayoub elou]

this all step for my injection  and materiel

[Rob]

Have you done any of the tutorials? Why wouldn't it be full of water?

[ayoub elou]

The problem is that when I define water in the material part, there is air present by default. And at the boundary conditions, it doesn't provide me with the option to input the velocity of water; it only allows for the velocity of the mixture phase.

[ayoub elou]

in cell zone donditions; i chose water it's CORRECT???n

[Rob]

Yes, correct. It's then a good idea to delete all unused materials to prevent their accidental use elsewhere in the model. 

[ayoub elou]

Yes, you're right. But when I try to delete the air material, it tells me that it's not possible to delete this material.

[Rob]

So, you need to find those zones and work out why they think they're air. Have you got overlapping mesh? The mid section in the above image looks odd. 

[ayoub elou]

You're right, I believe there is overlapping mesh because I have baffles inside my settler. I want to verify this.

[Rob]

That'll not help with the model.