•Direct Numerical Simulation (DNS)
–Theoretically, all turbulent (and laminar / transition) flows can be simulated by numerically solving the full Navier-Stokes equations
–Resolves the whole spectrum of scales. No modeling is required
–But the cost is too prohibitive! Not practical for industrial flows
•Large Eddy Simulation (LES) type models
–Solves the spatially averaged N-S equations
–Large eddies are directly resolved, but eddies smaller than the mesh are modeled
–Less expensive than DNS, but the amount of computational resources and efforts are still too large for most practical applications
•Reynolds-Averaged Navier-Stokes (RANS) models
–Solve time-averaged Navier-Stokes equations
–All turbulent length scales are modeled in RANS
Various different models are available
–This is the most widely used approach for calculating industrial flows
-ANSYS Training Manual-
INDOAERO 
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