# Governing Equations of Turbulent Flows - Lesson 4

Reynolds Averaged Navier-Stokes (RANS) equations are commonly used, instead of the actual Navier-Stokes equations, to understand the behavior of turbulent fluid flows. In this lesson, we will find out why that is the case (hint: Turbulent flows have a lot of structures of different length scales) and also derive the RANS equations.

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