A practical application of elements used in Aerospace Engineering. In the above picture set (from NASA), a model aircraft is placed in fluid with dyed liquid to model the flow of air around the craft. Cool!
Water tunnels are useful tools for determining aerodynamic characteristics of aircraft, such as this F-18 model placed in the NASA Dryden Flow Visualization Facility. By matching the Reynolds number of the model in the water tunnel to that of the full-scale aircraft in air, engineers can observe flow around the aircraft inside the laboratory. This similarity of flows is a powerful design tool. Here dye introduced along the nose, wings, and fuselage traces streamlines around the F-18, revealing areas of turbulence at different flight conditions.