Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/133

Rh by supposing a rigid boundary substituted for the fluid on the opposite side; Fig. 50 may therefore be read as representing the case of a cyclic motion round a filament in the neighbourhood of a plane boundary, superposed on a translation parallel to the boundary surface, and the energy required to produce such motion is finite.

§ 87. Numerical Illustration.—As a numerical illustration and a check on the foregoing, the author has estimated the energy in the plotting given in Fig. 48, in the region included in the external system within the circular limit indicated, being one of the lines of flow of the cyclic component. The number of squares in the component motions was calculated from the diameter of the circular limit, and the number in the combined system counted, fractions being estimated by a planimeter. The results are as follows:—