JAXA Supercomputer System Annual Report February 2025-January 2026

Report Number: R25EEG60100

Subject Category: Research and Development

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• Responsible Representative: Shuto Yatsuyanagi, Research and Development Directorate, Research Unit IV
• Contact Information: Shuto Yatsuyanagi(yatrsuyanagi.shuto@jaxa.jp)
• Members: Shuto Yatsuyanagi

Abstract

Hypersonic boundary-layer transition is a critical phenomenon in the design of atmospheric reentry vehicles and hypersonic cruise aircraft. At sufficiently high Reynolds numbers, the boundary layer undergoes transition from laminar to turbulent flow. Since the wall heat flux and skin friction in a turbulent boundary layer can increase by several times compared to those in a laminar boundary layer, accurate prediction of the transition location and the development of control strategies are indispensable for the design of thermal protection systems (TPS) and aerodynamic configurations. However, conventional linear prediction tools struggle to capture the relatively long nonlinear processes characteristic of hypersonic

transition, and currently, no predictive tool exists that is sufficiently reliable for design purposes.To achieve accurate transition prediction, a deeper understanding of the underlying transition mechanisms in hypersonic boundary layers is essential. The objective of this project is to elucidate the transition mechanism in the hypersonic boundary layer through numerical simulations.

Reference URL

N/A

Reasons and benefits of using JAXA Supercomputer System

Hypersonic boundary layer transitions are deeply intertwined with the growth process of flow disturbances, and their numerical calculations require high spatiotemporal resolution. High-order precision calculation schemes, as well as the use of large-scale computing resources such as JSS3, are essential for this project.

Achievements of the Year

In this study, two-dimensional axisymmetric numerical simulations were performed to investigate the disturbance growth process over a 7° half-angle cone under a high-enthalpy condition with a stagnation enthalpy of 9.4 MJ/kg. To evaluate the effect of freestream composition on the growth of Mack’s second-mode instability, computations were conducted for four cases with atomic oxygen mass fractions of 1%, 5%, 10%, and 23%, in addition to the air condition. Figure 1 shows instantaneous distributions of density and the magnitude of density gradient. In the downstream region of the flow, rope-like structures corresponding to large-amplitude second-mode waves are observed. Figure 2 presents the power spectral density (PSD) of density fluctuations for five freestream composition conditions. The density fluctuations were sampled at locations 1 mm away from the cone surface in the wall-normal direction at various streamwise positions. The results indicate that the PSD of the second mode decreases significantly as the atomic oxygen fraction in the freestream increases. This finding suggests that the presence of atomic oxygen suppresses disturbance amplification and may have a stabilizing effect on the transition process.

Fig.1: Power spectral density of density disturbances at different x coordinates and four different freestream compositions.

Fig.2: Instantaneous snapshots of the density and the magnitude of density gradient.

Publications

- Oral Presentations

1) Shuto Yatsuyanagi, Hideyuki Tanno, Influence of Atomic Oxygen in Freestream of High Enthalpy Shock Tunnel on Hypersonic Boundary Layer Transition, The 63rd Aircraft Symposium, 2025.

- Poster Presentations

1) Shuto Yatsuyanagi, Hideyuki Tanno, Influence of Atomic Oxygen in the Freestream on Hypersonic Boundary Layer Transition, Asia Pacific International Symposium On Aerospace Technology (APISAT 2025), Seoul, Korea.

Usage of JSS

Computational Information

• Process Parallelization Methods: MPI
• Thread Parallelization Methods: N/A
• Number of Processes: 912 - 3264
• Elapsed Time per Case: 72 Hour(s)

JSS3 Resources Used

Fraction of Usage in Total Resources*1(%): 0.59

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