Use case
It is a method of turbulence modeling where the Time Averaged Navier-Stokes equations are used.
This means that any property is split into its averaged and fluctuating components.
Rearranging and taking integral
The RANS Equations are formulated taking the Time Average of the Navier Stokes Equations
-
Continuity Equation
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Momentum Equations
Rearranging
$$
\boxed{
\frac{\partial \bar{u}_i}{\partial t}+\frac{\partial \bar{u}_i \bar{u}_j}{\partial x_j}=-\frac{1}{\rho} \frac{\partial \bar{p}}{\partial x_i}+\frac{\partial}{\partial x_j}\left[v \frac{\partial\bar u_i}{\partial x_j}+\tau_{i j}^{t u r b}\right]}
$$
where represents the Reynolds Stresses
References
Pg. 698 The Finite Volume Method - Moukalled