JAXA Supercomputer System Annual Report February 2025-January 2026

Report Number: R25ETET36

Subject Category: Skills Acquisition System

PDF (to be added)

• Responsible Representative: Takashi Aoyama, Specially Appointed Professor, Institute of Space and Astronautical Science, Dept. of Space Flight Systems
• Contact Information: Takashi Aoyama(aoyama.takashi@jaxa.jp)
• Members: Takashi Aoyama, Ryoki Chokawa, Yusei Nishi, Koto Nishimura, Hiroto Ogasawara

Abstract

We will establish a model-based design methodology for spaceplanes, and devise measures to improve the stability of atmospheric re-entry capsules and deployable flexible aeroshells entering the Martian atmosphere based on the understanding of the dynamic stability phenomena.

Reference URL

N/A

Reasons and benefits of using JAXA Supercomputer System

To conduct CFD analysis of entire spaceplanes and dynamic stability analysis of the capsules.

Achievements of the Year

As a CFD approach for hypersonic vehicle conceptual design, a hybrid unstructured mesh method using FaSTAR was evaluated. By introducing a prism layer aligned with the shock-wave geometry, numerical instability was mitigated. In simulations of the OREX configuration, the method achieved shock-capturing accuracy comparable to that of structured meshes (drag coefficient error: +0.9%) with a turnaround time of approximately 8 hours. In addition, a fundamental assessment of adaptive mesh refinement (AMR) for hypersonic flows was conducted. Using FaSTAR-AMR-REFINE—a coupled framework combining FaSTAR with the NASA AMR tool refine—the flow around a blunt cylinder at Mach 6.8 was analyzed. Because second-order calculations were difficult with an all-tetrahedral mesh, a hybrid mesh with prism layers placed ahead of the shock was introduced. This improved shock resolution and reduced the number of grid points by about 60% (from 6 million to 2.4 million).

In studies on capsule dynamic stability, aerodynamic analyses of forced and free oscillations were conducted to investigate the cause of unexpected oscillations of the Hayabusa2 Reentry Capsule in the subsonic regime. The results revealed significant differences between the turbulence model URANS and the hybrid models DES and IDDES. Furthermore, to compare the moving-grid and overset-grid methods, one-degree-of-freedom free-oscillation simulations of a thin-shell aeroshell were performed. The moving-grid method reduced computational time by more than a factor of 20 compared with the overset-grid method. Both approaches showed qualitative agreement with wind-tunnel experiments and successfully reproduced the damping of angle-of-attack oscillations.

Fig.1: Pressure contours of the flow around the reentry experimental vehicle (OREX) (top: present analysis; bottom: previous study). The hybrid mesh (right) eliminates the blurring observed with the all-tetrahedral mesh (left) and captures a sharp detached shock comparable to that obtained in the previous study using a structured mesh.

Fig.2: Comparison of Cp distributions around a blunt cylinder before and after AMR application.

Fig.3(video): Mach number distribution during forced oscillation of a Hayabusa-type capsule — an asymmetric flow field is observed in the wake.

Fig.4: Comparison of experimental and numerical results (moving-grid and overset-grid methods) for the one-degree-of-freedom free oscillation of a thin-shell aeroshell — both computational approaches show qualitative agreement with the wind tunnel results in terms of the damping of angle-of-attack oscillations.

Publications

N/A

Usage of JSS

Computational Information

• Process Parallelization Methods: MPI
• Thread Parallelization Methods: OpenMP
• Number of Processes: 240 - 1200
• Elapsed Time per Case: 72 Hour(s)

JSS3 Resources Used

Fraction of Usage in Total Resources*1(%): 1.08

Details

Please refer to System Configuration of JSS3 for the system configuration and major specifications of JSS3.

*1: Fraction of Usage in Total Resources: Weighted average of three resource types (Computing, File System, and Archiver).

*2: Fraction of Usage：Percentage of usage relative to each resource used in one year.

ISV Software Licenses Used

*2: Fraction of Usage：Percentage of usage relative to each resource used in one year.

JAXA Supercomputer System Annual Report February 2025-January 2026