[COMSOLZ]

Hello everybody,

so I have problem on hand, which I seem not to be able to solve on me own.

What is the problem about:
A microfluidic case is considered.
There is a bulk flow of water, which is driven by a shear-boundary on top. So far so good.
Now, there is a small cavity filled with air on the bottom, which is overflown with said water. The air should now be driven by the shear of the fluid-fluid-interface (like in a lit-driven cavity).

My problem:
In 2D I initialize the first fluid-zone to be filled with water. The second (the small cavity) to be filled with air.
A line shall model the f-f-interface. That interface is modelled as a "inner wall" and set to navier-slip-condition.

If I now solve and plot the streamlines, there is no movement in the air-filled cavity. This must be due to a not exiting coupling of the two phases.
I am not using the multiphase-module, because I don´t want the interface to move freely.

Best regards,
COMSOLZ