JAXA Supercomputer System Annual Report February 2025-January 2026

Report Number: R25ETET13

Subject Category: Skills Acquisition System

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• Responsible Representative: Kazuyuki Nakakita, Aviation Technology Directorate, Fundamental Aeronautics Research Unit
• Contact Information: Yoimi Kojima(kojima.yoimi@jaxa.jp)
• Members: Kota Abe, Kohei Konishi, Itsuki Miyamoto, Keita Ogura

Abstract

With the rapid development of urban UAVs, reducing aeroacoustic noise has become a critical challenge; however, the generation mechanisms involving complex flow phenomena are still not fully understood. This project aims to elucidate the correlation and generation mechanisms of boundary layer transition and associated acoustic phenomena through large-scale numerical simulations. By investigating dependencies on various conditions and conducting detailed physical analyses, we seek to obtain fundamental insights that contribute to improved noise prediction accuracy and low-noise aerodynamic design.

Reference URL

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Reasons and benefits of using JAXA Supercomputer System

The analysis of acoustic phenomena involving boundary layer transition is extremely computationally intensive, making a supercomputer indispensable for high-resolution, large-scale simulations. Its vast computational resources enable mesh refinement and parametric studies under various conditions, facilitating a detailed and systematic elucidation of the physical mechanisms.

Achievements of the Year

This study aims to elucidate the generation mechanism of tonal trailing-edge (TE) noise from a NACA0012 airfoil within the moderate Reynolds number and low Mach number range. This is a critical challenge for reducing the noise of small unmanned aerial vehicles (UAVs). Large-scale numerical simulations were conducted using JAXA's flow solver, FaSTAR, to evaluate the influence of ambient inflow turbulence on aeroacoustic characteristics. In the analysis, inflow turbulence was introduced near the airfoil using the Synthetic Turbulence Generation (STG) method. A comparative validation was then performed at two turbulence intensity levels under a unified turbulent integral scale.

The results confirmed that as the inflow turbulence intensity increased, there was a significant reduction in the peak intensity of the primary frequency components characteristic of tonal noise (Fig. 1). The primary frequency remained unchanged while the energy was redistributed across a broadband spectrum. Focusing on the separation zone near the trailing edge on the pressure side, which plays a dominant role in tonal noise generation, it was found that the location of the separation point was only minimally affected by turbulence intensity. However, the reattachment process involving turbulent transition within the separation zone was altered by the inflow turbulence (Fig. 2). These structural changes in the latter half of the separation zone are considered a potential factor that inhibits the acoustic feedback loop.

These findings improve the accuracy of UAV noise prediction in realistic operational environments with turbulence and provide important insights for future low-noise aerodynamic designs.

Fig.1: Comparison of pressure fluctuation spectra for different inflow turbulence intensities (*: "Weak" and "Strong" represent relative categories in this study and do not indicate absolute turbulence levels).

Fig.2: Comparison of time-averaged skin friction coefficient Cf distribution for different inflow turbulence intensities (Solid line: None, Dashed line: Weak, Dotted line: Strong / s.s.: Suction side, p.s.: Pressure side).

Publications

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Usage of JSS

Computational Information

• Process Parallelization Methods: MPI
• Thread Parallelization Methods: N/A
• Number of Processes: 1 - 4800
• Elapsed Time per Case: 192 Hour(s)

JSS3 Resources Used

Fraction of Usage in Total Resources*1(%): 0.67

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