Week 8: Literature review - RANS derivation and analysis

Reynold's stress: It is the component of the total stress tensor in a fluid flow that is obtained from the averaging operation over the Navier–Stokes equations to account for turbulent fluctuations in that same fluid momentum. It is basically the mean forces that are acting over per unit area of the fluid, imposed on the average flow by turbulent variations.

Turbulent viscosity: It is the part of diffusion that is seen in the fluid flow when the Renolds approch is applied on NS equations, which is the time integral of the the product of the fluctuations of velocities in x and y directions.

Molecular viscosity: It is also a part of diffusion that observes while NS equations are resolved by Renolds approch. But this term is discribed by the the product of viscosity and the diffrentiation of mean velocity in x-direction w.r.t y.