Day: October 23, 2016

Utilities in OpenFOAM

applyBoundaryLayer

Source Code: OpenFOAM-dev/applications/utilities/preProcessing/applyBoundaryLayer

Description
Apply a simplified boundary-layer model to the velocity and turbulence fields based on the 1/7th power-law.

The uniform boundary-layer thickness is either provided via the -ybl option or calculated as the average of the distance to the wall scaled with the thickness coefficient supplied via the option -Cbl. If both options are provided -ybl is used.

The velocity profile is initialized based on the 1/7th power law turbulent velocity profile:
\begin{equation}
\boldsymbol{u} = \boldsymbol{U} \left( \frac{y_w}{\delta} \right)^{\frac{1}{7}}, \tag{1}
\end{equation}
where \(\boldsymbol{U}\) is the main flow velocity, \(y_w\) is the distance to the wall and \(\delta\) is the boundary-layer thickness.

 

CFD Vision 2030 Study: A Path to Revolutionary Computational Aerosciences

I found very interesting technical report titled “CFD Vision 2030 Study: A Path to Revolutionary Computational Aerosciences” by NASA.

Abstract:

This report documents the results of a study to address the long range, strategic planning required by NASA’s Revolutionary Computational Aerosciences (RCA) program in the area of computational fluid dynamics (CFD), including future software and hardware requirements for High Performance Computing (HPC). Specifically, the “Vision 2030” CFD study is to provide a knowledge-based forecast of the future computational capabilities required for turbulent, transitional, and reacting flow simulations across a broad Mach number regime, and to lay the foundation for the development of a future framework and/or environment where physics-based, accurate predictions of complex turbulent flows, including flow separation, can be accomplished routinely and efficiently in cooperation with other physics-based simulations to enable multi-physics analysis and design. Specific technical requirements from the aerospace industrial and scientific communities were obtained to determine critical capability gaps, anticipated technical challenges, and impediments to achieving the target CFD capability in 2030. A preliminary development plan and roadmap were created to help focus investments in technology development to help achieve the CFD vision in 2030.

I want to read it thoroughly 🙂

Function Objects – DESModelRegions


In the case of Detached Eddy Simulations (DES), there are two regions in a computational domain that are treated in RANS-like and LES-like manners. The original Spalart-Allmaras DES model (DES97) formulation is based on the assumption that the wall-parallel grid spacing near the wall is in excess of the boundary-layer thickness \(\delta\) by a good margin so that the entire boundary layer can be handled by RANS [1].

Fig. 1 Natural DES grid in a boundary layer. Dotted line means velocity profile. \(\delta\) is the boundary-layer thickness [1].
Settings of DESModelRegions

In OpenFOAM, we can visually check these regions using the DESModelRegions function objects. It is also available in iconCFD.

If log it true, the volume percent (%) of RANS and LES regions will be output to the screen:

Source Code

Directory:
OpenFOAM-v1606+/src/postProcessing/functionObjects/utilities/
DESModelRegions

References

[1] P. R. Spalart, Detached-Eddy Simulation. Annual Review of Fluid Mechanics 41, 181-202, 2009.