Fig. 3. Wagner effect. The ratio of instantaneous to steady circulation (y-axis) grows as the trailing edge vortex moves away from the airfoil (inset), and its influence on the circulation around the airfoil diminishes with distance (x-axis). Distance is non-dimensionalized with respect to chord lengths traveled. The graph is based on fig. 35 in Walker (1931). The inset figures are schematic diagrams of the Wagner effect. Dotted lines show the vorticity shedding from the trailing edge, eventually rolling up into a starting vortex. As this vorticity is shed into the wake, bound circulation builds up around the wing section, shown by the increasing thickness of the line drawn around the wing section.

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