Hello everyone,
My goal is to know how accurate is my simulation using the Wall Modeled Large Eddy Simulation (WMLES) S-omega and to calculate the total turbulent kinetic energy.
Therefore I would like to know if I'm resolving 80% of the turbulent kinetic energy with my grid and to do that I need to compute the SGS turbulent kinetic energy and compute the ratio between the resolved and total turbulent kinetic energy (k_resolved / (k_resolved + k_sgs) )
Assuming the resolved turbulent kinetic energy can be calculated by:
- k_resolved = 0.5 * (U_RMSE ^2 + V_RMSE ^2 + W_RMSE ^2 )
Is there a way to compute k_sgs using the various parameters given by Fluent ?
The turbulent parameters that Fluent has available are:
- Subgrid Turbulent Viscosity
- Subgrid Effective Viscosity
- Subgrid Turbulent Viscosity Ratio
- Subgrid Filter Length
- Effective Thermal Conductivity
- Effective Prandtl Number
- Wall Yplus
The article referenced in the Fluent user theory guide is (PDF) A hybrid RANS-LES approach with delayed-DES and wall-modelled LES capabilities (researchgate.net)
According to the guide, the subgrid filter length is given by the equation (4) and the subgrid turbulent viscosity is given by equation (19).
Thank you for reading,
There is a Beta Feature in Fluent 2022 that estimates LES quality. However it is not clear which models (any LES and DES) the equation 10.3 (Fluent 2022 Beta Features Manual) can be used.
k_modeled = (µ_tSGS/(0.3*ρ))*S
Where µ_tSGS is subgrid-scale eddy viscosity, rho is density and S is strainrate magnitude.
For example, there are some models that don't output the subgrid-scale eddy viscosity.
Greetings.
Depending on the type of simulation that is performed, many features appear. In the “run calculation” tab, the variables can be extrapolated, and more parameters can be added. These are located by pressing the “other/add variables” button. In case what you need does not appear, it can be accessed through the console and even perform the operations you mention. However, there are many hidden options, perhaps you can find some more information in the user guide. Remember that it is commercial software, which means that it is closed source and many of the calculations are black box, so what you are looking to calculate would be very complicated.
- Badges
- Science topic