Turbulence is a difficult flow characteristic to define. Typically turbulence is thought of as some kind of randomness or measure of chaos occurring in a flow. Laminar flow by contrast is ordered, characterized by smooth, parallel layers. Whether a flow is turbulent or laminar is typically defined by the Reynold’s number of the flow: $Re=\dfrac{\rho VL}{\mu}$ Where $V$ and $L$ are some characteristic [[Velocity|velocity]] and length scale for the given flow type. A critical Reynold’s number exists for different flow geometries which signals the transition from laminar to turbulent flow. Reynold’s numbers below this critical number will be classified as laminar and above this critical number will be classified as turbulent. For pipe flow the critical number is usually taken to be around 2300. The characteristic length scale for pipe flow is the pipe inner diameter, and the characteristic velocity is the average [[Fluid|fluid]] velocity through the pipe at a given cross-section.