The Spalart-Allmaras model is a one-equation model that solves the transport equation for kinematic eddy viscosity.
This model is specifically designed for aerospace applications related to flow around walls and provides reasonably good solutions for boundary layer flows under adverse pressure gradients. It’s also becoming increasingly popular in turbomachinery modeling.
Developed for aerodynamic flows, this model has limitations in handling free shear flows, particularly in plane and round jets, and it cannot predict the decay of isotropic, homogeneous turbulence.
Here is the transport equation for the Spalart-Allmaras model:
(6.5)
With ν̃ as the transported variable, G,nu represents turbulent viscosity production, and Y,nu denotes turbulent viscosity destruction occurring in the near-wall region.
Sigma,nu and C,b2 are constants, and ν is molecular kinematic viscosity, while S,nu stands for the source term. It can be observed that κ is not considered, thus the estimation of Reynolds Stress is neglected in the final term.
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