[3absamad]

Hello everyone,

I'm pretty new to FLUENT however I've some basic knowledge that I had couple of simulations running..

from the key point that a correct problem setup is very important in having accurate results and a converged solution I want couple of help on my problem setup:

first of all I'm simulating a helical micro swimmer with an attached magnet, a full rigid body to be correct in a channel, 3D simulation.
what you should know the helical swimmer is pretty much small, the total length is around 2mm and helix diameter around 0.5 mm.
so my current setup is:

1. The swimmer is defined as a wall inside an enclosure which is pretty big compared to the size of the robot cylinder radius is r = 25 mm and length L = 25 mm,

2. the mesh is pretty much basic here are the details:
1591798 tetrahedral cells, zone 3, binary.
1591798 cell partition ids, zone 3, 4 partitions, binary.
3150278 triangular interior faces, zone 2, binary.
2270 triangular wall faces, zone 1, binary.
63890 triangular wall faces, zone 8, binary.
238 triangular pressure-outlet faces, zone 7, binary.
238 triangular velocity-inlet faces, zone 6, binary.
284959 nodes, binary.
284959 node flags, binary.

3. Pressure based solver
4. I use standard k-epsilon model with default values.
5. Inlet velocity of 1 m/s and gauge pressure of 0 Pa
6. Outlet gauge pressure is also 0 Pa
7. the wall of the robot is specified to be rotating at 5 rad/s (I want to simulate from 5 rad/s till 100 rad/s to plot a graph of rad/s and net moments and forces)

around 400 iterations I reach a converged solution, however at enclosure of 30 mm radius and length of cylinder I didn't get a converged solution message at even 20,000 iterations.

My questions are:
*Is the enclosure/domain okay? or big? should it be smaller? (smaller means lower number of iterations for converged solution message)

*Is the model I'm using okay? or should I use another turbulence model? because it's a low Reynolds number?

*When I say that the wall is rotating, does it move at a certain axial velocity because of propulsive force? or remains stationary? should I define the wall functions using a UDF to specify that the wall is rigid body and allows all 6DOF motion?

Thanks a lot in advance, I'm using the simulation before I go to practical tests as we are working on a research paper.

[jacky831]

can you give us some pictures of model?

[3absamad]

Originally Posted by jacky831

can you give us some pictures of model?

if there's anything else that needs clarification, please tell me.

Thanks a lot in advance