Fluid is flowing with an average velocity of $$V$$ through a pipe of diameter $$d.$$ over a length of $$L,$$ the “head” loss is given by $${{fL{V^2}} \over {2gD}}.$$ The friction factor, $$f,$$ for laminar flow in terms of Reynolds number ($$Re$$) is ______________ (fill the blank)

For a fully developed laminar flow through a pipe, the ratio of the maximum velocity to the average velocity is ___________ (fill in the blank)

Existence of velocity potential implies that

For a fluid element in a two dimensional flow field ($$x-y$$ plane), it will undergo