Multiphase flow problem
I created a simple 2D geometry to simulate the rainwater flow on a pavement. I have used a side inlet for water to enter other than from the top (right side).
I also have a drain. Before starting the simulation, I filled this drain with water using patch technique (shown below). My problem is, when I start running the program with a very small inlet water velocity, my water in drain displaces heavily, even though I want it to be still. I did not apply velocity to the water in drain. My bottom is a stationary wall. Can I know why this happens and how to overcome it?