In the official tutorial, in the example of vertical flaps, when I set the density of the solid to be close to the fluid density, divergence occurs. Is it caused by the additional mass effect? Even if I set up an implicit coupling scheme and use aitken acceleration. If someone could answer, I would greatly appreciate it.
@fan_wu yes, this is probably something you cannot work around. Implicit coupling with Aitken/IQN helps a lot, and you can tune the algorithms and the time stepping a lot, but you cannot completely work around the added mass effect in all scenarios.
What is your use case for densities of solid and fluid too close to each other?