Response of erythrocytes using 2 way FSI?

[Mitra Lanka]

Hi,
I am working on a 2-way Fluid structure interaction project related to RBC in capillaries.

I have designed a micro-scale shell RBC and a fluid medium which has diameter just above the dia of RBC. In the transient structural analysis I have defined two fluid surface interfaces: 1. Exterior portion of RBC 2. Interior portion of RBC.

In the Fluent medium I have defined the walls, boundaries of capillary tube and cytoplasm (hollow portion of RBC) which are supposed to interact with with the solid RBC in Transient. I have assumed that blood runs at x velocity and cytoplasm relatively at 0.97x velocity.

Similarly, in transient I have 0.97x velocity, 9.7x displacement to Solid RBC When I run the analysis by coupling both systems I receive error by doing so. But if I reduce the time step (0.0004) sec for 10 sub-steps ,velocity to 0.0000097x and displacement by 0.000097x solution runs smoothly.

Irrespective of correctness of result, Could anyone tell me why is that if i decrease the velocity, displacement and time steps there is result and why if i consider real time scenario this does not work?

Thanks

 

[Baluncore]

Most simulation systems will have problems with small clearances with high speeds because the discrete time steps needed become very short and it takes too much time to solve the matrices.

Is this a question about ANSYS Fluent simulation software ?