Reynolds number — UPSC Physics Optional CSE 1995 Paper I

Distinguish between stream-line motion and turbulent motion. Hence define Reynold’s number. A sphere of radius 0.1\text{ cm} moves through glycerine. A laminar flow is observed when the velocity of the sphere does not exceed 15\text{ cm/s}. At what minimum velocity of a sphere of radius 5\text{ cm} will the flow in water become turbulent? Viscosity coefficient for glycerine \eta_{\text{gly}} = 14\text{ p} and for water \eta_{\text{wat}} = 0.011\text{ p}, and density of glycerine = 1.2\text{ gm/cc}.