JAXA Supercomputer System Annual Report February 2025-January 2026

Report Number: R25EACA12

Subject Category: JSS Inter-University Research

PDF (to be added)

• Responsible Representative: Keiichi Kitamura, Professor, Yokohama National University
• Contact Information: Takuya Hanami(hanami-takuya-rs@ynu.jp)
• Members: Takuya Hanami, Keiichi Kitamura, Yujiro Noji, Hayato Sato

Abstract

Research on the practical application of reusable rockets is being actively pursued to reduce space transportation costs. Unlike conventional expendable rockets, reusable rockets must perform a return flight after their mission. This study aims to clarify the aerodynamic characteristics of the vehicle during the return phase through numerical analysis and wind tunnel testing. By comparing experimental and computational results, we conduct mutual validation and acquire aerodynamic data, while flow visualization from the simulations elucidates the aerodynamic behavior during reentry. In particular, this fiscal year focused on investigating the dynamic aerodynamic characteristics under periodic angle-of-attack variations in the range of 0 to 90 degrees, which correspond to the vehicle's pitch-over maneuver required prior to landing for aerodynamic performance improvement, as well as validation against wind tunnel test results.

Reference URL

N/A

Reasons and benefits of using JAXA Supercomputer System

We used JSS3 because we treated fluid calculations that require an enormous amount of computation time on a normal workstation. Large-scale unsteady calculations involving a continuously evolving flow field, in which the angle of attack varies periodically over a range of 0 to 90 degrees, can be completed in a realistic amount of time by using JSS3. Visualization of the flow fields of the numerical fluid calculations allows us to investigate not only the aerodynamic characteristics of the reusable rocket during its pitch-over maneuver, but also the formation mechanisms of those aerodynamic characteristics at each angle of attack.

Achievements of the Year

Numerical fluid calculations assuming gliding flight during the return phase were conducted using a slender body that simulates a reusable rocket. While previous studies assumed a constant pitch-over rate, this year's calculations employed a sinusoidal pitch-over rate approximating actual flight conditions, thereby enabling a more realistic elucidation of the flow field. The following two findings were obtained. (1) Flow field patterns consistent with those observed in experiments conducted under the same conditions were obtained. It was confirmed that attached flow occurs at low angles of attack [Fig.1], a symmetric vortex pair forms at around 45 degrees [Fig.2], an asymmetric vortex pair develops at around 80 degrees [Fig.3][Fig.4], and a vortex shedding flow field appears at higher angles of attack. (2) Comparison with static calculations revealed that the flow field patterns described in (1) occur with a delay in the dynamic calculations relative to the static ones. This indicates that the flow field tends to be sustained in dynamic calculations.

Fig.1: Attached flow at an angle of attack of 20 degrees

Fig.2: Symmetric vortex pair at an angle of attack of 45 degrees

Fig.3: Flow field at an angle of attack of 80 degrees

Fig.4: Asymmetric vortices at an angle of attack of 80 degrees

Publications

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Usage of JSS

Computational Information

• Process Parallelization Methods: MPI
• Thread Parallelization Methods: N/A
• Number of Processes: 480 - 3840
• Elapsed Time per Case: 168 Hour(s)

JSS3 Resources Used

Fraction of Usage in Total Resources*1(%): 0.17

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