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)

As the transition from laminar to turbulent flow is induced in a cross flow past a circular cylinder the value of the drag coefficient drops.

The necessary and sufficient condition which brings about separation of boundary layer is
$${{dP} \over {dx}} > 0$$

Two insulting materials of thermal conductivity $$K$$ and $$2K$$ are available for lagging a pipe carrying a hot fluid. If the radial thickness of each material is same