(Refer Slide Time: 41:41)
If I say u is equal to phi x, v is equal to phi y and w is equal to 0 and I can always say that this is the two dimensional flow. And in that case also I have a velocity potential, in that case the corresponding equation, continuity equation will give me del square phi by del x square plus del square phi by del y square is equal to 0, that I for a two dimensional flow two dimensional flow. Now, in this we have understood by now what is a velocity potential? what is a vortex free motion? what is irrotational motion?