Stationary mesh interface causing divergence in FSI sim.
 

Hi all,

Attachment 47299

I'm modeling a complex system that includes pipe flow. The pipe is in sections such that the fluid in the pipe meets another fluid zone via fluid-fluid interfaces. [The fluid domain of the pipe must be in separate sections for dynamic remeshing settings purposes.] What's happening is the outside surface of the fluid is in motion with the structure of the pipe via FSI, but the faces of the fluid-fluid interfaces remain stationary such that part of the domain is moving, and part of it isn't, which results in poor element quality/divergence. The image above shows the deformation of a small section of the pipe's fluid domain.

How might I avoid this circumstance? I want the fluid-fluid interfaces (and fluid zones between them) to move with the structure - I do not want stationary interfaces. The motion of the pipe's structure is not known; I want the fluid-fluid interfaces to move freely as I cannot predict what their motion should be.

Thank you,
Kegan