Flow in simple geometry does not converge

It's been my first day with Comsol and it's CFD package, so please don't be too hard on me. I have (succesfully, I believe) built my first geometry. It consists of a tube that has several inlets on one side and is open on the other side.

Now I want a fluid (air) to enter through the biggest inlet in the middle and see how it develops. Unfortunately, I get an error saying that the Newton Iteration did not converge. Can anybody help? The file is attached below.