In a diagnostic exam on fluid mechanics, in which students are asked to draw flow diagrams of a simple geometry case, there is an apparent confusion associated to reference frame changes. As a didactic tool, we propose a comparative analysis of flow diagrams on different relative movement conditions of the same system, consisting in a cylindric pipe containing liquid and a small spherical object. Such diagrams are velocity maps and streamlines obtained through numerical solutions of Navier-Stokes equation.
flow patterns; streamlines; velocity maps; reference frames; numerical solutions
