OpenFOAM 2.0.0: Turbulence Modelling

Dynamic Lagrangian Model

The latest release includes the new dynLagrangian large eddy simulation (LES) turbulence model, a Lagrangian two equation eddy-viscosity model. In LES, large turbulent structures in the flow are resolved by the governing equations, while the effect of the sub-grid scales (SGS) are modelled. Conventional models predict SGS viscosity with a model constant, e.g. Smagorinsky’s constant . Dynamic models attempt to estimate SGS turbulence from the solution of the large turbulent structures, or in other words, estimate  from the flow itself. Estimates are commonly based on spatial averaging, e.g. across the solution domain or planes of the flow. The Lagrangian approach instead estimates SGS turbulence from larger calculated turbulent structures that are being transported with the flow, using two transport equations with relaxation.

Source code

• incompressibleLESModels library
  $FOAM_SRC/turbulenceModels/incompressible/LES/dynLagrangian

Wall function modelling

Validation testing has been undertaken on wall function modelling and several refinements have been added to the latest version of OpenFOAM. The new version also includes a wall function boundary condition, nutUTabulatedWallFunction, for turbulent kinematic viscosity that uses tabulated data of dimensionless velocity  as a function of near-wall Reynolds number .

A new utility wallFunctionTable also exists to generate a table of data that can be looked up by the tabulated wall function boundary conditions. More specifically, the utility writes solution data of the form  to produce data in the form .

A new kappatJayatillekeWallFunction boundary condition has been added that provides a thermal wall function for incompressible flows.

Source code

• incompressibleRASModels library
  $FOAM_SRC/turbulenceModels/incompressible/RAS/derivedFvPatchFields
• wallFunctionTable utility
  $FOAM_UTILITIES/preProcessing/wallFunctionTable