Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/116

§ 74 barrier in the opposite direction, and it will only be possible to recognise the resultant flow; thus, as before, if Fig. 39 represent the two superposed streams by the lines a a a and b b b, the flux across the imaginary barrier line e f, due to the stream a, will be equal and opposite to the flux across the same line due to the stream b, consequently there is no resultant flux across the line e f, which is therefore one of the lines of flow of the resultant system. Likewise in the case of the other parallelograms, so that the field c c c is the resultant system.

We therefore see that the superposition of two independent streams has the same resultant as the superposition of two motions on one stream.

The foregoing constitutes the basis of a comprehensive method