Hello I am modeling horizontal placed rectangular open microchannel with height, width, and length of 2 , 15, and 100 micrometers. The mesh is hexahedral mesh with all quadrilateral and consist of inlet, outlet and atmospheric(top of he rectangle) boundary condition.

In General section choose pressure-based and transient time. By marking absolute velocity. In setup use VOF model, which includes open channel flow, coupled level set method and Implicit body forces. Taking air as a primary phase and water as secondary phase. In which interaction include surface tension between water and air of 0.0735 mN/mM.

I am putting drop of water in contact with open microchannel. In boundary condition, inlet(water) is pressure inlet with volume fraction 1. outlet (mixture of water and air) is pressure outlet with 0 volume fraction. Atmospheric(air) as pressure outlet. In all this boundary condition I select open channel flow in the multi-phase option with free surface level 2 micrometer. Also, choosing operating density by default. By considering mixture for Wall Zone with stationary wall, no slip condition with wall adhesion between water and air of 90 degree.

Solution method, scheme - PISO, gradient - least square cell based, pressure - presto, Momentum - quick, Volume frcation - Implicit scheme.

Solution Initialization, Compute from - Inlet and initialize it. In patch select water and variable volume fraction with value 1 and zone to patch is liquid.

Run calculation with time step 1.0e+6 microsecond with 1000 iteration.

Please, help me if anything wrong in the above explanation of model. In this, I want to find out how much time fluid takes to travel through the end of channel with the effect of capillary force. But, I didn't got the correct results. Also, it gave me a reverse flow.

Questions;

Questions;

Where should, I deposit 5 micro liter water droplet in BC's ?

Why, I am not able to define contact angle between liquid and wall ?

So. I hope somebody help me on this. Thank you in advance.