Please describe what you are trying to simulate with a lot more details. Insert an image or a sketch to help explain it. Why do you want to see the air flow on the object? What is it that you want to calculate in the simulation? Why do you need mass on the objects?

The usual way to have a 2D or 3D object have mass in a simulation is for the material to be given the Physical Property of Density. Then the analysis will compute the mass from the volume of the object.