CFD Simulations AC1-09: Difference between revisions
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'''Application Challenge AC1-09''' © copyright ERCOFTAC {{CURRENTYEAR}} | '''Application Challenge AC1-09''' © copyright ERCOFTAC {{CURRENTYEAR}} | ||
==Solution Strategy== | ==Solution Strategy== | ||
Detached Eddy Simulations (DES) have been performed by a number of partners in | |||
the EU-project ATAAC. DES (Spalart, 2009) is a hybrid RANS--LES approach that | |||
was originally based on the Spalart--Allmaras (SA) model, but that has also been | |||
extended to $k$--$\omega$ models. In DES switching between LES and RANS is | |||
effectively achieved by defining the turbulence length scale employed in the | |||
turbulence model as the minimum of the LES and RANS length scales. The LES | |||
length scale is the filter width, which is defined as the maximum of the mesh | |||
size in all three computational directions at each grid point. The RANS length | |||
scale depends on the RANS model employed: essentially the wall distance for the | |||
SA model and $\sqrt{k}/\omega$ for the $k$--$\omega$ model. Note that for the SA | |||
model the RANS length scale is static and therefore the RANS--LES interface is | |||
fixed, whereas for the $k$--$\omega$ model the RANS--LES interface is dynamic. | |||
Computations have been performed with different DES-type methods as listed in | |||
Table \ref{ref-models}. For the underlying RANS model, the SA model (SA-DES; | |||
Spalart \emph{et al.}, 1997), the SST $k$--$\omega$ model (SST-DES; Travin | |||
\emph{et al.}, 2002), and the TNT $k$--$\omega$ model (X-LES; Kok \emph{et al.} | |||
2004) have been employed. The main difference between SST-DES and X-LES is that | |||
in SST-DES the blended turbulent length scale is only used to define the | |||
dissipation term in the $k$-equation, whereas in X-LES it is used to define the | |||
dissipation term as well as the eddy-viscosity coefficient. The delayed approach | |||
of Spalart \emph{et al.} (2006), shielding attached boundary layers against | |||
inadvertently switching to LES (so-called shear-stress depletion), is used in | |||
all DES and X-LES computations (denoted as DDES and DX-LES) but one. Finally, | |||
CFSE has employed the improved variant IDDES (Shur \emph{et al.}, 2008). Table | |||
\ref{ref-models} also lists the type of solvers and grids. | |||
==Computational Domain== | ==Computational Domain== | ||
Revision as of 13:35, 12 March 2015
Vortex breakdown above a delta wing with sharp leading edge
Application Challenge AC1-09 © copyright ERCOFTAC 2024
Solution Strategy
Detached Eddy Simulations (DES) have been performed by a number of partners in the EU-project ATAAC. DES (Spalart, 2009) is a hybrid RANS--LES approach that was originally based on the Spalart--Allmaras (SA) model, but that has also been extended to $k$--$\omega$ models. In DES switching between LES and RANS is effectively achieved by defining the turbulence length scale employed in the turbulence model as the minimum of the LES and RANS length scales. The LES length scale is the filter width, which is defined as the maximum of the mesh size in all three computational directions at each grid point. The RANS length scale depends on the RANS model employed: essentially the wall distance for the SA model and $\sqrt{k}/\omega$ for the $k$--$\omega$ model. Note that for the SA model the RANS length scale is static and therefore the RANS--LES interface is fixed, whereas for the $k$--$\omega$ model the RANS--LES interface is dynamic.
Computations have been performed with different DES-type methods as listed in Table \ref{ref-models}. For the underlying RANS model, the SA model (SA-DES; Spalart \emph{et al.}, 1997), the SST $k$--$\omega$ model (SST-DES; Travin \emph{et al.}, 2002), and the TNT $k$--$\omega$ model (X-LES; Kok \emph{et al.} 2004) have been employed. The main difference between SST-DES and X-LES is that in SST-DES the blended turbulent length scale is only used to define the dissipation term in the $k$-equation, whereas in X-LES it is used to define the dissipation term as well as the eddy-viscosity coefficient. The delayed approach of Spalart \emph{et al.} (2006), shielding attached boundary layers against inadvertently switching to LES (so-called shear-stress depletion), is used in all DES and X-LES computations (denoted as DDES and DX-LES) but one. Finally, CFSE has employed the improved variant IDDES (Shur \emph{et al.}, 2008). Table \ref{ref-models} also lists the type of solvers and grids.
Computational Domain
Boundary Conditions
Application of Physical Models
Numerical Accuracy
CFD Results
References
Contributed by: J.C. Kok, H. van der Ven, E. Tangermann, S. Sanchi, A. Probst, L. Temmerman — '
© copyright ERCOFTAC 2024