different types of Turbulence Modelling approaches

Turbulence

1. RANS : Reynolds-averaged Navier-Stokes is a widely used turbulence model that averages the turbulent quantities in space and time. RANS models solve the time-averaged Navier-Stokes equations and provide statistical information about the turbulent flow field. RANS models are computationally efficient and can be used for a wide range of applications. However, RANS models are limited by their inability to capture unsteady structures in turbulent flows.

2. LES : Large Eddy Simulation is a turbulence modeling approach that resolves the large-scale turbulent structures and models the small-scale turbulence using a subgrid -scale model. LES models provide accurate predictions of unsteady flows and are particularly useful for flows with large-scale coherent structures, such as turbulence in boundary layers, jets, and wakes. However, LES models are computationally expensive and require a fine grid resolution, which can be challenging for complex geometries and high-Reynolds-number flows.

3. DNS : Direct Numerical Simulation is a turbulence modeling approach that solves the Navier-Stokes equations without any turbulence modeling assumptions . DNS models provide the most accurate predictions of turbulent flows and are particularly useful for fundamental studies of turbulence. However, DNS models are computationally very expensive and are limited to low-Reynolds-number flows and simple geometries.

4. DES : Detached Eddy Simulation is a hybrid RANS-LES model that combines the advantages of both approaches. DES models use RANS equations in the near-wall regions, where the flow is typically smooth, and LES equations in the outer regions, where the turbulence is dominant. DES models are computationally efficient and provide accurate predictions of wall-bounded flows and unsteady flows. However, DES models can be sensitive to grid resolution and require careful calibration of the model constants .