[Mahmoud_aboukhedr]

Dear Foamers, Hopefully all are doing well with simulations,
Am facing a big problem using interFoam to simulate oil slug mobilization in capillary tube filled with water for very low capillary numbers (range of 1e-8), I will try to explain the case as clear as I could so I can get the proper help,
The experimental paper I have is describing the oil mobilization on middle section of a capillary tube of dimension (0.5mm*400mm*0.5mm), and the imposed flow rate is in the range of (1e-10 t0 1e-13 m^s), for which it represent a very low capillary number. The experimental paper shows the development of the oil slug shapes as shown int the attached file (1A).

Here is the important part, I am trying to simulate the same experimental case in my PhD, but am facing a big failure.
My simulation conditions are as following,
- Imposed volume flow rate at the inlet and atmospheric pressure at the outlet.
- Constant contact angle at the walls with value of theta=145
- The slug is initialized as box in the begging of the tube as shown in (2A)

The slug never deform like the experiment at low flow rate, at low flow rate the slug take the droplet shape at the first time steps and then start to move along the tube, while if I increase the flow rate the trailing edge of slug deform and separate see picture 3A for comparisons

The question
1) Why at low flow rate the interface curvature is wrong, and why at high flow rate it deform and does not limited by the constant contact angle.
2) Why the contact line at low flow rate is wrong? also I tried the dynamic contact angle but it does not work too.
3) How can I correct for the interface curvature in interFoam for viscous driven flow?

I Am sorry for asking to many questions, (maybe they are stupid) but I will appreciate any help on that matter.