V3.1: Streamlines Past an Airfoil

(Related to Textbook Section 3.1 - Newton's Second Law)

Streamlines are lines everywhere tangent to the fluid velocity. For steady flow the streamlines coincide with the pathlines that fluid particles follow. That is, for steady flow, streamlines are the same as the paths taken by dye injected into the flow.

The streamlines for very slow flow past a model airfoil are made visible by injecting dye as several locations upstream of the airfoil. By closely observing the flow of the dye, it can be seen that the fluid speed varies along a given streamline. Thus, there is a component of acceleration along the streamline. In addition, many of the streamlines are curved. Hence there is also a component of acceleration normal to the streamlines.