Filling air-filled microtube with Water using VOF

Ybes

Hello everyone,

i am trying to fill a small 2-D tube/chamber with inlet width of 1.5 mm, initially filled with air, with water. Inlet Velocity is 0.0005 m/sec.. Outlet is set as Pressure-Outlet. I am using the VOF-model and spalart-Allmaras or Low-Re-k-e-model, as Re<200. Wall-adhesion is enabled. To allow higher sub-time steps i coarsened the grid, so that a time-step of 1e-4 is (larger time-step is however risky) possible. This still takes a lot of computational time, but i can't find a better way to speed up the simulation. i set the operating pressure to 101325 and outlet pressure to 100, i am not sure if these pressure values are correct. Can anyone help me please?