Numerical Analysis of Space Launcher Wake Flows

RWTH Aachen University (Germany)

Principal Investigator: Wolfgang Schröder, Institute of Aerodynamics (AIA)

Project Description

On 12 December 2002, the maiden flight of the European heavy space launcher ARIANE 5 ECA equipped with the new VULCAIN 2 engine failed due to a deterioration of the main stage nozzle. The analysis of the flight data revealed that one of the aggravating factors that led to the accident was the non-exhaustive definition of the loads to which the new VULCAIN 2 engine is subjected during the flight trajectory into space.

Fig. 1 Instantaneous Mach number distribution around the generic Ariane 5-like configuration computed using a zonal RANS-LES method.
Copyright: AIA, RWTH Aachen University (Germany)

The tail of a classical space launcher, e.g., the ARIANE 5, TITAN 4, H-II to name a few, includes an abrupt junction between the main body and the attached rocket engine causing the boundary layer to separate on the base shoulder. At the early transonic phase of the flight the turbulent shear layer shed from the main body impinges on the nozzle just upstream of its end, which due to high dynamic pressure values leads to significant wall pressure fluctuations. Associated with these pressure fluctuations, unsteady aerodynamic forces with pronounced low-frequency peaks, known as the buffet phenomenon, arise which can lead under unfavorable conditions to a complete loss of the space transportation vehicle, as in the aforementioned accident. The steadily increasing demand for communication and navigation satellites and the growing competition in the aerospace market, requires more efficient and reliable transport facilities into the orbit. Therefore, accurate numerical tools validated by high-fidelity experimental investigations are required to provide detailed insight into the wake flow phenomena, to develop methods of their control, and to ultimately reduce aerodynamic loads on the nozzle structure without penalizing the launcher‘s efficiency. Unfortunately, unlike the rocket inner engine flow, the wake flow of a real launcher cannot be analyzed in full-scale on the ground, leading to increased safety margins and consequently, a reduced launcher efficiency.

Within the project, a large number of various configurations including planar space launchers as well as axisymmetric free flight configurations were analyzed at varying freestream (trans-, supersonic) conditions, to improve the understanding of the complex interaction and superposition of different periodic and stochastic flow phenomena, including the not yet fully understood buffet phenomenon. In addition, the effect of passive flow control devices on the wake of a generic planar model was investigated.

The time-resolved numerical simulations of the flow field around the space launcher configurations are performed using a zonal RANS-LES approach. Therefore, the computational domain is split into two zones. In the zones with an attached flow, the Reynolds-averaged Navier-Stokes (RANS) equations are solved and in the wake region a large-eddy simulation (LES) is performed (see Fig. 1). Using such a hybrid approach combined with structured grids an efficient time-resolved computing of high Reynolds-number wake flows at a fraction of the costs of a pure LES is realized.

The flow solver is optimized for the HLRS HPC system using hybrid parallelization based on MPI and OpenMP. Furthermore, parallel I/O procedure using HDF5 is employed. Since the buffet phenomenon is characterized by low frequency pressure oscillations, the required number of time steps per simulation is extremely high to sufficiently resolve these low frequency modes. For example, the analysis of the wake flow of an Ariane 5-like configuration, using a zonal setup with approximately 500 Mio. grid points, a total number of 14.6 Mio. core hours distributed over approximately 10,000 cores have been used. The statistical data requires about 100 TB of disk space.

Fig. 2 Wake flow topology of the investigated configurations: (a)Free-flight configuration; instantaneous spanwise vorticity distribution (top); time-averaged axial velocity profiles and streamlines (bottom). (b) Planar configuration with passive flow control.
Copyright: AIA, RWTH Aachen University (Germany)

Through the computational resources provided by the Hazel Hen system at the HLRS and highly optimized solvers, the influence of dynamic velocity variations could be investigated in representative three-dimensional domains for binary and ternary systems. These investigations increased the understanding of the rearrangement and adjustment processes in the microstructures required for the tailored development of materials with changing, locally defined microstructures.


The authors gratefully thank for the financial support within the project SKAMPY (Ultra-scalable multiphysics simulations for solidification processes in metals) founded by BMBF, the cooperative graduate school "Gefügeanalyse und Prozessbewertung" by the ministry of Baden-Wuerttemberg and the Helmholtz graduate school "Integrated Materials Development for Novel High Temperature Alloys".

Scientific Team

Johannes Hötzer, Michael Kellner, Willfried Kunz, Britta Nestler (PI)


[1] K. A. Jackson and J. D. Hunt. Lamellar and rod eutectic growth. Transactions of the Metallurgical Society of AIME, 236:1129-1142, 1966.

[2] J. Hötzer, P. Steinmetz, A. Dennstedt, A. Genau, M. Kellner, Irmak Sargin, and B. Nestler. Influence of growth velocity variations on the pattern formation during the directional solidification of ternary eutectic Al-Ag-Cu. 136:335-346, 2017.

[3] P. Steinmetz, J. Hötzer, A. Dennstedt, C. Serr, and B. Nestler. Investigation of three-dimensional microstructure rearrangement during ternary eutectic directional solidi cation of Al-Ag-Cu. Journal of Crystal Growth, page submitted, 2017.

[4] J. Hötzer. Massiv-parallele und großskalige Phasenfeldsimulationen zur Untersuchung der Mikrostrukturentwicklung. Ph.d. dissertation, Karlsruher Institut für Technologie (KIT), 2017.

[5] A. Dennstedt, L. Helfen, P. Steinmetz, B. Nestler, and L. Ratke. 3D Synchrotron Imaging of a Directionally Solidified Ternary Eutectic. Metallurgical and Materials Transactions A, pages 1-4, 2015.

[6] J. Hötzer, M. Kellner, P. Steinmetz, and Nestler B. Applications of the phase-field method for the solidification of microstructures in multicomponent systems. 96(3):235-256, 2016.

[7] M. Kellner, I. Sprenger, P. Steinmetz, J. Hötzer, B. Nestler, and M. Heilmaier. Phase-field simulation of the microstructure evolution in the eutectic NiAl-34Cr system. 128:379 - 387, 2017. ISSN 0927-0256. doi: URL

[8] P. Steinmetz, Y. C Yabansu, J. Hötzer, M. Jainta, B. Nestler, and Surya R Kalidindi. Analytics for microstructure datasets produced by phase-field simulations. 103:192-203, 2016.

[9] J. Hötzer, M. Jainta, P. Steinmetz, B. Nestler, A. Dennstedt, A. Genau, M. Bauer, H. Köstler, and U. Rüde. Large scale phase-field simulations of directional ternary eutectic solidification. 93(0):194 - 204, 2015. ISSN 1359-6454. doi: 10.1016/j.actamat.2015.03.051. URL

[10] A. Vondrous, M. Selzer, J. Hötzer, and B. Nestler. Parallel computing for phase-field models. 28(1):61-72, 02 2014. ISSN 1094-3420. doi: 10.1177/1094342013490972. URL

[11] J. Hötzer, A. Reiter, H. Hierl, P. Steinmetz, M. Selzer, and B. Nestler. The parallel multi-physics phase-field framework pace3d. 2017 (submitted).

[12] C. Godenschwager, F. Schornbaum, M. Bauer, H. Köstler, and U. Rüde. A framework for hybrid parallel flow simulations with a trillion cells in complex geometries. In Proceedings of SC13: International Conference for High Performance Computing, Networking, Storage and Analysis, page 35. ACM, 2013.

[13] M. Bauer, J. Hötzer, M. Jainta, P. Steinmetz, M. Berghoff, F. Schornbaum, C. Godenschwager, H. Köstler, B. Nestler, and U. Rüde. Massively parallel phase-field simulations for ternary eutectic directional solidification. In Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis, page 8. ACM, 2015.

[14] M. Kellner, J. Hötzer, P. Steinmetz, K. Dargahi Noubary, W. Kunz, and B. Nestler. Phase-field study of microstructure evolution in directionally solidified NiAl-34Cr during dynamic velocity changes. pages 372-375, 2017.

[15] M. Kellner, W. Kunz, P. Steinmetz, J. Hötzer, and B. Nestler. Phase-field study of dynamic velocity variations during directional solidification of eutectic NiAl-34Cr. 2017 (submitted).

[16] P. Steinmetz, M. Kellner, J. Hötzer, A. Dennstedt, and B. Nestler. Phase-field study of the pattern formation in Al-Ag-Cu under the influence of the melt concentration. 121:6-13, 2016.

[17] J. Hötzer, P. Steinmetz, M. Jainta, S. Schulz, M. Kellner, B. Nestler, A. Genau, A. Dennstedt, M. Bauer, H. Köstler, and U. Rüde. Phase-field simulations of spiral growth during directional ternary eutectic solidification. 106:249 - 259, 2016. ISSN 1359-6454. doi: URL

[18] K. Dargahi Noubary, M. Kellner, P. Steinmetz, J. Hötzer, and B. Nestler. Phase-field study on the effects of process and material parameters on the tilt angle during directional solidification of ternary eutectics. 138:403 -411, 2017. ISSN 0927-0256. doi:

[19] P. Steinmetz, J. Hötzer, M. Kellner, A. Dennstedt, and B. Nestler. Largescale phase-field simulations of ternary eutectic microstructure evolution. 117:205-214, 2016. doi: 10.1016/j.commatsci.2016.02.001.

[20] P. Steinmetz, M. Kellner, J. Hötzer, and B. Nestler. Quantitative comparison of ternary eutectic phase-field simulations with analytical 3D Jackson-Hunt approaches. 11 2017. ISSN 1543-1916. doi: 10.1007/s11663-017-1142-2. URL

[21] P. Steinmetz. Simulation der bei der gerichteten Erstarrung ternärer Eutektika entstehenden Mikrostruktur mit der Phasenfeldmethode. Ph.d. dissertation, Karlsruher Institut für Technologie (KIT), Diss., 2017.

[22] J. Hötzer, M. Jainta, M. Ben Said, P. Steinmetz, M. Berghoff, and B. Nestler. High Performance Computing in Science and Engineering '15: Transactions of the High Performance Computing Center, Stuttgart (HLRS) 2015, chapter Application of Large-Scale Phase-Field Simulations in the Context of High-Performance Computing, pages 659-674. Springer International Publishing, 2016. ISBN 978-3-319-24633-8. doi: 10.1007/978-3-319-24633-8 42. URL

[23] J. Hötzer, M. Jainta, M. Bauer, P. Steinmetz, M. Kellner, H. Köstler, U. Rüde, and B. Nestler. High Performance Computing in Science und Engineering - Garching/Munich 2016 (2016), chapter Study of complex microstructure evolution in ternary eutectic alloys with massive parallel large-scale phase-field simulations. Bayerische Akademie der Wissenschaften, 2016. URL

[24] J. Hötzer, M. Kellner, P. Steinmetz, J. Dietze, and B. Nestler. High Performance Computing in Science and Engineering '16: Transactions of the High Performance Computing Center, Stuttgart (HLRS) 2016, chapter Large-scale phase-field simulations of directional solidified ternary eutectics using high-performance computing. Springer International Publishing, 2017.

[25] A. Choudhury and B. Nestler. Grand-potential formulation for multicomponent phase transformations combined with thin-interface asymptotics of the double-obstacle potential. Physical Review E, 85(2):021602, 2012.

[26] M. Plapp. Unified derivation of phase-field models for alloy solidification from a grand-potential functional. Physical Review E, 84(3):031601, 2011. [27] M. Ruggiero and J. Rutter. Origin of microstructure in the 332 K eutectic of the Bi-In-Sn system. Materials science and technology, 13(1):5-11, 1997.

[28] A. Dennstedt and L. Ratke. Microstructures of directionally solidified Al-Ag-Cu ternary eutectics. Transactions of the Indian Institute of Metals, 65 (6):777-782, 2012. ISSN 0972-2815. doi: 10.1007/s12666-012-0172-3. URL

Project Team and Scientific Contact

M.Sc. Simon Loosen, Dr.-Ing. Matthias Meinke, Prof. Dr.-Ing. Wolfgang Schröder (PI), Dr.-Ing. Vladimir Statnikov

Institute of Aerodynamics, RWTH Aachen University
Wüllnerstraße 5a, D-52062 Aachen (Germany)

February 2018