convergence for u.x not reached after 100 iterations

[SigmaYot Zeta]

Dear all,

I'm a beginner with Basilisk software. I built my own simulation based on the official example (https://www.basilisk.fr/src/examples/sphere.c), changing 1 ball to 6 balls. The simulation run successfully, but it does not converge, and the mgu solver has to iterate to 100 times. A little confused.

The log is as follows,

0 0 0 0
src/poisson.h:219: warning: convergence for u.x not reached after 100 iterations
  res: 0.0039811 sum: 588.121 nrelax: 100 tolerance: 0.001
1 0.01 3 100

My code and geometry files are shown in attachments.

I feel this problem isn't complicated, but it's been bothering me for days. I don't know what settings I'm doing wrong, and I hope an experienced user can give me some pointers.

Thanks for your attention.

[Stephane Popinet]

Hi,

There are two main problems with your file:

- at line 39 you are not setting the viscosity properly, it should be:

muv.x[] = fm.x[]*0.001;

see examples/sphere.c

- I assume you want to compute the flow _around_ the spheres and not
_inside_ the spheres. If so your solid surface is not oriented properly.
You can fix this by changing line 59 to

solid(cs, fs, - (dist[] ... )/8.);

cheers,

Stephane