JAXA Supercomputer System Annual Report February 2025-January 2026

Report Number: R25ECMP36

Subject Category: Competitive Funding

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• Responsible Representative: Hideaki Nanri, Research and Development Directorate, Research Unit IV
• Contact Information: Shun Takahashi Research and Development Directorate, Research Unit IV(takahashi.shun@jaxa.jp)
• Members: Mika Edahiro, Masaaki Fukui, Chihiro Fujio, Kaito Hirose, Kosuke Hamaji, Yuki Hirayama, Taku Inoue, Ryota Kobayashi, Noriko Katsumura, Kota Matsuhashi, Toshihiko Munakata, Kei Norimatsu, Koutarou Nakayama, Shinji Nakaya, Ikuo Ozawa, Takuma Tadokoro, Shunsuke Takamatsu, Masahiro Takahashi, Shun Takahashi, Takuto Yamaguchi

Abstract

This project will develop fundamental technologies primarily using computational fluid dynamics (CFD), carried out within the framework of the research and development task titled "Flight Demonstration of Robust Low-Sonic-Boom Aircraft Design Technology and Ground Demonstration of Engine Design Technology with a Wide Operating Range" under the K Program "Development of Key Technologies for the Advancement of Supersonic and Hypersonic Transport Systems." Specifically, we will conduct numerical analyses at each university that has signed the "Memorandum of Understanding Regarding Ground-Based Verification of Engine Design Technologies with a Wide Operating Range," focusing on analyses requiring numerous parameter studies and long-duration combustion simulations.

Reference URL

Please refer to https://www.jst.go.jp/k-program/program/koukuu2.html .

Reasons and benefits of using JAXA Supercomputer System

The purpose of this project is to design and develop core technologies aimed at achieving stable operation of hypersonic engines across a wide speed range; consequently, it involves combustion analysis and numerous parameter studies, resulting in extremely high computational costs. Furthermore, since the design process involves analyses using tools such as FaSTAR, developed by JAXA, the project is highly compatible with JAXA's supercomputers. Given these backgrounds and reasons, there is significant value in utilizing JAXA's supercomputers.

Achievements of the Year

A RANS analysis was performed on a scramjet engine model combustor to clarify the influence that the flow bent by the strut has on the flow field inside the cavity (Fig. 1). An LES analysis was performed on a ramjet engine model combustor, and it was confirmed that under high-temperature mainstream conditions, a flame appears between the fuel injector and the V-gutter flame holder, and qualitative agreement with the experimental results was confirmed (Fig. 2).

To support the design and evaluation of an intake applied to a turbine-based combined-cycle engine, the following three investigations were conducted (Figs. 3-4):

• Performance improvement of the subsonic diffuser in the turbo-ramjet engine flow path

• Verification of the mass-flow matching between the turbo-ramjet flow path and the engine

• Investigation of methodologies for applying FaSTAR-Move to the evaluation of turbine-based combined-cycle engines

Fig.1: Pressure and streamline (non-reactive), changing main flow Mach number, L/D, and presence or absence of struts

Fig.2: Heat release rate distribution in a model ram combustor under assumed flight Mach numbers of Ma2 or Ma3.5

Fig.3: Effect of subsonic diffuser improvement on total pressure recovery and intake length

Fig.4: Comparison of numerical results of the intake flow field at low Mach numbers with a theoretical model

Publications

- Oral Presentations

Kotaro Nakayama, Kaito Hirose, Takuma Tadokoro, Kengo Takizawa (University of Tokyo), Sadatake Tomioka (JAXA), Shinji Nakaya, Mitsuhiro Tsue (University of Tokyo) "Combustion Characteristics of High-Temperature Jet Fuel in a Ramjet Model Combustor with V-gutters under a Mainstream Total Temperature of 750 K" 65th Aerospace Propulsion and Space Propulsion Symposium, 2026

Shunsuke Takamatsu, et al., "The Performance Improvement of Subsonic Diffuser Applied to Turbo-ram / Scram Combined Cycle Engine", JSASS Northern Branch 2026 Annual Meeting and the 7th Symposium on Reusable Space Transportation Vehicles Northern Branch of the Japan Society for Aeronautical and Space Sciences, 2026

Ryota Kobayashi, et al., "Performance Analysis of a Variable Inlet for Hypersonic Combined Cycle Engines in Turbo–Ramjet Operating Modes", Proceedings of the Space Sciences and Technology Conference, 2025

Usage of JSS

Computational Information

• Process Parallelization Methods: MPI
• Thread Parallelization Methods: N/A
• Number of Processes: 500 - 5000
• Elapsed Time per Case: 200 Hour(s)

JSS3 Resources Used

Fraction of Usage in Total Resources*1(%): 0.75

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