Superposition of Elementary Flows

One question that naturally arises is "Why are we discussing these flows such as uniform flow, source flow vortex and doublet flows when they do not actually exist. The answer is "Yes, they do not exist. But conceptually they are useful.". In fact, they serve as alphabets of potential flow. By combining these flows we can build up more complicated flows, which are meaningful.

We note that the flows we have discussed are linear flows. By linearity it is meant that if A and B are two solutions, even $mA\pm nB$ (where m and n are numbers) is also a solution. Therefore we are allowed to superpose the elementary flows one above the other to obtain a different flow. If the constituent flows are irrotational, the combined flow too is irrotational.

The student is advised to run the following programs which plot streamlines and velocity potential lines for various cases of superposition.

streamf.exe

velpot.exe

(c) Aerospace, Mechanical & Mechatronic Engg. 2005
University of Sydney