JAXA Supercomputer System Annual Report February 2025-January 2026

Report Number: R25EACA21

Subject Category: JSS Inter-University Research

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• Responsible Representative: Keiichi Kitamura, Supervisor Prof. Yokohama national university
• Contact Information: Kota Tanikawara(tanikawara-kota-pc@ynu.jp)
• Members: Ryounosuke Hoshi, Seiichiro Kobayashi, Keiichi Kitamura, Kota Tanikawara

Abstract

Previous studies investigated a slender body geometry simulating a typical rocket and clarified the effects of protuberances on supersonic aerodynamic characteristics and the surrounding flow field through computational fluid dynamics CFD and wind tunnel experiments. In this study it was found that the side force coefficient reaches its maximum at an angle of attack alpha 15 deg. It was also revealed that neither interference effects among multiple blunt protuberances nor an increase in side force due to an increase in the width of the blunt protuberance were observed. Furthermore methods to reduce the side force generated by a blunt protuberance were examined and it was demonstrated that placing a ring shaped protuberance upstream of the blunt protuberance is effective in reducing the side force. However this configuration resulted in a significant increase in axial force which remained an issue.

To suppress the increase in axial force while reducing the side force a VG was installed at positions symmetric to the blunt protuberance location where the side force becomes maximum in order to intentionally generate vortices. The effects of the VG sideslip angle and VG height on axial and side forces were investigated. In the wind tunnel experiments conducted at an angle of attack of 15 degrees the side force reduction effect was evaluated and the VG sideslip angle that significantly reduces the side force was identified. Numerical simulations yielded results consistent with those obtained in the wind tunnel experiments.

Reference URL

N/A

Reasons and benefits of using JAXA Supercomputer System

Numerical fluid simulations are being conducted to understand the aerodynamic characteristics of a rocket equipped with protuberances. To mitigate the increase in side force caused by the installation of protuberances, a vortex generator (VG) is placed at asymmetric positions to actively intervene in the flow field and reduce the side force.

This study requires numerical simulations for a vast number of test cases; therefore, JSS3 is utilized to perform the computations efficiently. The CFD results show good agreement with the wind tunnel experimental results. Furthermore, by analyzing and visualizing the numerical results, the spatial flow field—difficult to capture in wind tunnel experiments—can be clarified in detail.

Achievements of the Year

Numerical simulations were performed using a slender body model simulating a rocket with a protuberance as shown in Fig. 1 at an angle of attack of 15 degrees and freestream Mach numbers of 0.7 and 1.3. In addition, a vortex generator VG was installed on the slender body shown in Fig. 1 at positions symmetric to the protuberance location. As VG parameters the installation angle and height of the VG were varied to investigate the side force reduction effect. As a result it was clarified that the side force decreases as shown in Fig. 2. Furthermore the flow field around the body was visualized using numerical simulation results. For example by visualizing the density gradient as shown in Fig. 3 shock waves and expansion waves were clearly identified.

Fig.1: Body configuration.

Fig.2: Side force coefficient at freestream Mach numbers 0.7 and 1.3 with vortex generator installed.

Fig.3: Schlieren visualization from the wind tunnel experiment and density gradient visualization from numerical simulation.

Publications

- Oral Presentations

Kobayashi S., Kitamura K., "Numerical Analysis of Cyclorotor Rotation Speed and Blade Angle", 63th Aircraft Symposium, 2025.

Tanikawara, K., Kakimoto, H., Oonawa, Y., Kitamura, K., and Nonaka, S.; Transonic Wind Tunnel Tests on the Effect of Vortex Generator Configuration on the Side Force Characteristics of a Slender Body, Symposium on Flight Mechanics and Astrodynamics, 2025.

- Poster Presentations

Tanikawara, K., Kitamura, K., and Nonaka, S.; Lateral and Axial Force Control by Installing Micro Protuberance on a Supersonic Rocket, the 56th JSASS Annual Meeting, 2025.

Tanikawara, K., Kitamura, K., and Nonaka, S.: Lateral and Axial Force Control by Installing Micro Protuberance on a Supersonic Rocket, 35th ISTS, Asty Tokushima, Jul. 2025.

Usage of JSS

Computational Information

• Process Parallelization Methods: MPI
• Thread Parallelization Methods: N/A
• Number of Processes: 480 - 3840
• Elapsed Time per Case: 72 Hour(s)

JSS3 Resources Used

Fraction of Usage in Total Resources*1(%): 0.11

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