maximum packing limit for eulerian multiphase
 

I try to model transient solid-gas flow in bubbling bed. I wish to find heat transfer characteristics of the bubbling bed. Some specifications of my model :
Eulerian multiphase model
realizable k-e turbulence model with realizable wall functions.
velocity inlet and pressure outlet.
I defined glass beads as granular materials and specified max. packing limit as 0.63 (as default). However, in some regions the volume fraction of solid particles exceeds the maximum packing limit. The residuals for continuity is about 10^-4. In fact, in some regions, the volume of reaction approaches to 1 which is physically impossible because of spherical shape of the particles. The diameter of the particles 275 micron.
My solver settings:
Phase coupled SIMPLE with N-phase volume fraction equations. I both use green gauss cell based and least squares cell based spatial discretization schemes. All other variables are set to first order upwinding, I gradually increase the order as solution convergence and time passes.
Is there anyone who face with this problem before ? I am also open to the advices about convergence issues. I am looking forward to your replies.

Hi~

Did you patch a region of glass beads in the domain?
or initially the whole domain is full of gas?

Yes, I patched it and the volume fraction approaches to 1.

It seems that the volume fraction distribution in the domain is weird when "N-phase volume fraction equations" is checked.
But in the manual I didn't find the description about the way to use it properly.

Hi ,

unfortunately I can not help you :( because I am a beginner in this kind of work, but I think you can help me :) if you don't mind .I am a student of 2nd year master, I'm working on fluent.16 software for the simulation of fluidization (without combustion or chemical reaction) this fluidized bed uses the olive pomace as particles and air as the fluidizing. I draw the geometry of the boiler and I did the mesh but I found a lot of trouble about modeling (in fluent models), I try to understand but really it's not easy), please if you don't mind help me with advice or paper that can help me to advance in my project. I tried with documentation of ansys but it is too detailed and
scattered.
thank you for any help :)

I am not familiar with multi-phase models, but I think you can try to describe the problem and let people help you.

I have few question relating to Euler-Lagrangian simulations. I am analyzing solid-liquid flow at 90 degree elbow in pipe with both techniques Euler-Euler and Euler-Lagrangian and i want to see what is the difference in results by using both techniques.



1) In Euler-Euler approach there is an option to mention what is the volume fraction of secondary phase. But in case of Euler-Lagrangian approach how do i mention that my secondary phase is this much?


2) If i want to compare my results for Euler-Euler and Euler-Lagrangian approach then which parameter should i compare. I was comparing maximum pressure in elbow for Euler-Euler and Euler-Lagrangian approach but i found out that i can find it in Euler-Euler approach but in case of Euler-Lagrangian approach it is not available. Only pressure available was of liquid phase which was solved by Eulerian method. So, my question is how can i measure the combine pressure due to both phases.


Please do reply, I will really appreciate.

1. Could you tell me where is the option? Is it a Boundary Condition or something?

2. Multi-phase Models treat the secondary phase as particles. That's why you can find out that you have to set up the "Diameter" of the secondary phase. However, the particles are considered as "continuous" as fluid in Multi-phase Models, while DPM model treat them as "discrete".
Thus you can go to the manual and try to find the definition of "pack limit" shown in the secondary phase setup window when "Granular" is checked.
You can also find the Limitation about the solid fraction of these two model described in the manual.

3. DPM treat the particles as "particles without volume in the cell". However, the effect of its size on the fluid, such as Drag, could be described using other equations to interact with the fluid (primary phase only, in my memory) --> Check "Update DPM sources Every Flow Iteration".

yes it is in B.C multiphase tab when u turn on some multiphase model.