Reynolds number ~ MECHTECH GURU

Reynolds number

Reynolds number

Reynolds number is a pure number, which determines the type of flow of a liquid, whether a streamline flow or a turbulent flow through a cylindrical pipe. It has no units and dimensions. It is given by the expression

Reynolds number (R) =  ρV D /η

where V is velocity of the liquid, ρ is the density of the liquid, η is the coefficient of viscosity of the liquid and D is the diameter of the pipe. This equation is applicable only for liquids flowing through cylindrical pipe.

Experiments show that the flow of a viscous liquid is laminar or streamlined, if Reynolds number is less than 2000. The flow of a viscous liquid is turbulent if Reynolds number is more than 2800. Between 2000 and 2800 there is a transition region in which the flow may change from streamline to turbulent.

Narrow tubes and highly viscous liquids tend to promote streamline motion, while wider tubes and liquids of low viscosity leads to turbulence.

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