# How can I tell whether my flow is laminar or turbulent?

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The Reynolds number parameter determines whether the given flow is laminar or turbulent. Laminar flow occurs at low Re (where the viscous forces are dominant) and is characterized by smooth fluid motion. Turbulent flow, on the other hand, occurs at high Re (where the inertia forces are dominant) and is characterized by chaotic fluid motion with lots of mixing and eddies.

• You can use the following ranges as reference to understand if your flow is laminar, turbulent or transitional. However, they are not hard limits. The transition can happen earlier or later depending on surface smoothness and other factors.

For an internal flow:

Re < 2300 - The flow is laminar

Re > 4000 - The flow is turbulent

For extenal flow:

Re<1x10^5  - The flow is laminar

Re>5x10^5  - The flow is turbulent

• Thanks you all for your quick replies! @prajput @Kremella

I have another question, how can I calculate the Reynolds number?

• The Reynolds number is mathematically defined as:

Re = (rho * V * L) / mu

where,

rho is the fluid density

V is the fluid velocity

L is the problem characteristic length scale

mu is the fluid dynamic viscosity

• Don't forget to read up on the Rayleigh Number for buoyant flows.