2 phase flow in a flexible microchannel
 

I am working in ANSYS 14 , fluid solid interaction for simulating a droplet flowing through a micro channel.A small part of the channel is flexible.Its dimension is varying from 25*25 um2 to 10 *25 um2.
Time step = 2e10(-6).
velocity = 0.01 m/s
phase = water droplet in mineral oil.
under relaxation parameter used in system coupling:0.2 for both data transfer
for meshing I am using automatic meshing option available in work bench,ANSYS.
The problem I am facing :
though my fluid part in fluent and structural part in transient structural is getting converged.But in system coupling it is not reaching the convergence criteria 0.01.It is oscillating around 0.1 as the droplet getting closer to the constriction and sometimes even before that.

increase the number of elements . or there might be problem with solution methods in fluent