## How do I choose a turbulence model in Openfoam?

If RAS is selected, the choice of RAS modelling is specified in a RAS sub-dictionary which requires the following entries.

- RASModel: name of RAS turbulence model.
- turbulence: switch to turn the solving of turbulence modelling on/off.
- printCoeffs: switch to print model coeffs to terminal at simulation start up.

**What is a low Reynolds number model?**

A low Reynolds number model is a model that correctly reproduces the limiting behaviors of various flow quantities as the distance to the wall approaches zero. So, a low Reynolds number model must, for example, predict that k~y2 as y→0.

### What is the difference between K Epsilon and K-Omega?

K epsilon is best suited for flow away from the wall, say free surface flow region, whereas k-omega model is best suited for near the wall flow region, where adverse pressure gradient is developed.

**Can I use turbulence model for laminar flow?**

If the flow is turbulent then using a laminar flow model should not converge. If it does then you may be using an excessively coarse mesh, too much stabilization, or loose convergence tolerances. Unsteady vortices should be triggered in the model but they cannot be resolved with any reasonable mesh resolution.

#### What is K in OpenFOAM?

Turbulent kinetic energy, k, Turbulent kinetic energy dissipation rate, \epsilon.

**What is nut in OpenFOAM?**

The class nutWallFunction is a base class that parents the derived boundary conditions which provide a wall constraint on various fields, such as turbulent viscosity, i.e. nut , or turbulent kinetic energy dissipation rate, i.e. epsilon , for low- and high-Reynolds number turbulence models.

## What is Reynolds number for water?

32 483

In our Reynolds number calculator, we choose (as a substance) water at 10 °C and we obtain Reynolds number Re = 32 483 .

**Why is k-epsilon a turbulence model?**

K-epsilon (k-ε) turbulence model is the most common model used in computational fluid dynamics (CFD) to simulate mean flow characteristics for turbulent flow conditions. It is a two equation model that gives a general description of turbulence by means of two transport equations (partial differential equations, PDEs).

### Can I use K-Epsilon model for laminar flow?

k-epsilon based models cannot handle k=0 so they do not degenerate to laminar flow well.

**What is SST k Omega?**

The SST k-omega turbulence model is a two-equation eddy-viscosity model that is used for many aerodynamic applications. It is a hybrid model combining the Wilcox k-omega and the k-epsilon models. A blending function, F1, activates the Wilcox model near the wall and the k-epsilon model in the free stream.