Use Reynolds Number for Pipe Flow to find Whether it is Laminar Flow or Turbulent Flow

Pipe flow can be laminar flow or turbulent flow. Turbulent flow is characterized by high flow velocity and low fluid viscosity. It occurs for Reynolds number greater than 4000. Laminar Flow occurs for Reynolds Number less than 2100 and is characterized by low flow velocity and high fluid viscosity. Reynolds Number for pipe flow is given by Re = (diam)(velocity)(density)/viscosity. For flow in non-circular conduits, the pipe diameter in the expression for Reynolds Number is replaced by four times the hydraulic radius, where hydraulic radius equals (cross-sectional area of flow)/(wetted perimeter). See an example calculation in this article.