ERCOFTAC Bulletin - Centre Acoustique

were performed at the same cluster, which showed
a 8 times better performance for both solvers. This
is probably due to load changes on the system. The
tests furthermore showed, that the overall performance
for this particular test case is at its optimum between
4 and 8 NoisSol processes coupled to 4 PIANO processes.
Currently under examination is a sudden instability
in the near field, which occurred after
tsim ≈ 9.0 ≈ 260000 dt for pure NoisSol and
≈ 4.6 ≈ 135000 dt for PIANO+. Due to the long
period of successful computation this is probably related
to a strong, source triggered disturbance.
Figure 3: Sound pressure level, NoisSol, PIANO+ and
Lockhard [5]
Figure 4: Pressure field, uncoupled computation, t=2.0
5 Conclusion
The presented DG scheme was applied to the
NASA 30P30N airfoil noise test case as stand-alone
solver and in a coupled framework. The results are very
encouraging from the qualitative and quantitative point
of view and proved the operability of the scheme. To
improve the applicability a reliable examination of the
performance behavior of the coupled scheme for different
Figure 5: Pressure field, coupled computation, t=2.0
Uncoupled Coupled
Code NoisSol NoisSol
nDegF r 0.747e6 0.28e6
dx 0.002 . . . 0.2 0.002 . . . 0.01
tsim 9.03 4.61
tCP U 1840 1370
tCP U/ 27.3e-5 106e-5
(nDegF r · tsim)
Coupled
Code PIANO Combined
nDegF r 6.57e6 6.85e6
dx 0.004
tsim 4.61 4.61
tCP U 1370 2750
tCP U/ 4.53e-5 8.70e-5
(nDegF r · tsim)
Table 2: Computation times
CPU distributions and in comparison to the uncoupled
scheme is necessary.
Acknowledgement
This work has been done with the kind support of the
Institute of Aerodynamics and Flow Technology (IAS)
at the German Aerospace Center (DLR), in particular
Professor Jan Delfs and Dr. Roland Ewert, who delivered
the acoustic sources for the calculations and made their
PIANO code available for the coupling framwork.
References
[1] M. Dumbser: Arbitrary High Order Schemes for the
Solution of Hyperbolic Conservation Laws in Complex
Domains. PhD thesis, Universität Stuttgart
(2005)
[2] G. J. Gassner, F. Lörcher, C.-D. Munz and J. S. Hesthaven:
Polymorphic nodal elements and their application
in discontinuous Galerkin methods. JCP
228, Issue 5 (2009)
[3] F. Lörcher, G. Gassner and C.-D. Munz: Arbitrary
High Order Accurate Time Integration Schemes for
Linear Problems. ECCOMAS CFD (2006)
[4] D. P. Lockard and M. M. Choudhari: Noise Radiation
from a Leading-Edge Slat. AIAA paper 2009-
3101 (2009)
32 ERCOFTAC Bulletin 90