ERCOFTAC Bulletin - Centre Acoustique

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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
[5] D. P. Lockard and M. M. Choudhari: The Effect of Cross Flow on Slat Noise. AIAA paper 2010-3835 (2010) [6] R. Ewert: Broadband slat noise prediction based on CAA and stochastic sound sources from a fast random particle mesh (RPM) method. Computers & Fluids 37 (2008) [7] R. Ewert and W. Schröder: Acoustic Perturbation Equations based on Flow Decomposition via Source Filtering. JCP 188 (2003) [8] A. Birkefeld and C.-D. Munz: A Hybrid Method for CAA. Proc. of the 36. Jahrestagung für Akustik der Deutschen Gesellschaft für Akustik DAGA, Berlin (2010) [9] A. Birkefeld and C.-D. Munz: Advances in Numerical Aeroacoustics with the Discontinuous Galerkin Solver NoisSol. Proc. of the 17. Symposium der Strömungsmechanischen Arbeitsgemeinschaft STAB, Berlin (2010) [10] J. Delfs, M. Bauer, R. Ewert, H. Grogger, M. Lummer and T. Lauke: Numerical Simulation of Aerodynamic Noise with DLR’s aeroacoustic code PIANO. Manual, IAS DLR Braunschweig (2007) [11] J. S. Hesthaven and T. Warburton: Nodal Discontinuous Galerkin Methods: Algorithms, Analysis and Applications. Springer Verlag, New York (2008) ERCOFTAC Bulletin 90 33
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