## Fluids

#### Sparger setup, Airlift reactor

• Jamessmp23
Subscriber

Hello all,

I tried to simulate the airlift bioreactor using euler-euler multiphase method with k-epsilon standard for study the flow patterns but got stuck at the sparger setup.
Does fluent can setup the desire bubble diameter and flow rate from the sparger (frame motion from the solid geometry) or do I have to draw a geometry with many small tube for the gas inlet.
Can anyone suggest sparger, airlift reactor on ANSYS fluent tutorials ? or any suggestion about the method that I used ?

Thank you
Sumit Peh

Ansys Employee

Hello,

You can use eulerian multiphase model. Please define phases correctly.

Regards,

Keyur

• DrAmine
Ansys Employee

Hi,

The video shared by Keyur is good start for you. The bubble diameter is an input which needs to be provided by you. You can imagine that bubbles might grow, collapse and coalescence with other bubbles and this might require a dynamic bubble diameter definition. All this can be done in Fluent.

there is no explicit tutorial for Airlift reactor in Fluent but you can find several papers where Fluent or CFX has been used for for the simulation parts.

• Jamessmp23
Subscriber

Hello Keyur,

Thank you so much for quick reply, I had followed this step by step, the simulation ran perfectly without any error but the result was incorrect. Air does not flow into the reactor. I set the inlet boundary condition as air velocity = 0.2 m/s, volume fraction = 0 and for water velocity = 0. For the outlet boundary condition, I set as an out flow.

My simulation is different from this tutorial. I want to simulate 3D airlift reactor which already has water inside the reactor (without water flow in or out) then flow air bubble (d=0.005m) to generate the airlift circulation system in the reactor.
I selected the primary phase as water so I can edit the diameter on the secondary phase(air) but still I cannot patch the water volume = 1 on the initialize section.

I'm confuse about patching water volume fraction = 1 in the fluid domain, does it means I put the water in the reactor ? do I need to patch it ?

Thank you,

Sumit

• DrAmine
Ansys Employee

If you initialize with zero volume fraction for air then the reactor is completely filled with the pimary phase: water.

Ansys Employee

Yes, as Amine pointed out, you can patch vof of water with value 1 or vof of air with value zero.

Regards,

Keyur

• Jamessmp23
Subscriber

I had tried patched the volume of air = 0 or volume of water = 1, the result is air cannot flow into the reactor.

For now I patched the volume of air in the fluid domain as 0.2, the result is air can flow and circulated in the reactor but still have the problem on flow patterns from the draft tube, so now I comparing on the meshing step which are (1) set draft tube geometry as constructed geometry (2) set as default and mesh sizing (1e-2).

Thank you to all for replying back, I will check this topic as Is Solution.

Regards,

James

• gbosh
Subscriber

I am new to fluent and I am having a difficult time getting the right circulation for my airlift reactor simulation. I have used a 2D geometry, the Euler-Euler multi-phase method, k-epsilon for turbulence. I set the inlet boundary condition as air velocity = 0.25 m/s and zero for water, volume fraction for air as 1. But it seem not to recirculate and has a very funny flow pattern. it won't go through the riser. I was finally able to get it to go through the riser using the eulerian model and setting the outlet to degassing, but still no re-circulation.