JAXA Supercomputer System Annual Report February 2025-January 2026

Report Number: R25EDU10509

Subject Category: Space and Astronautical Science

PDF (to be added)

• Responsible Representative: Akira Oyama, Professor, Institute of Space and Astronautical Science
• Contact Information: Akira Oyama(oyama.akira@jaxa.jp)
• Members: Makoto Sato, Takahumi Hirose, Taichi Matsumoto, Yohei Takahashi, Akira Oyama

Abstract

To realize aerial observation on Mars, various types of Mars aircraft have been explored worldwide. In Japan, ISAS/JAXA has been leading various research and development projects on Mars aerial vehicles, including Mars airplanes and Mars helicopters.

Meanwhile, with the rapid development of electric vertical takeoff and landing (eVTOL) aircraft in recent years, new configurations such as vector-thrust-type and lift-and-cruise-type eVTOLs are being considered for application to Mars aerial vehicles, in addition to conventional fixed-wing airplanes and helicopters.

Under these circumstances, a research group led by Shima at JAXA has conducted experimental studies toward the realization of a new vector-thrust-type winged eVTOL, referred to as the Passive Pendulum Body (PPB) eVTOL. Their experiments have provided insights into an eVTOL configuration that combines a simple mechanical structure with high aerodynamic performance. Applying such an eVTOL concept to a Mars aircraft is expected to improve cruise endurance and enable wide-area scientific observations.

However, in these experiments, it remains difficult to obtain detailed flow field data around the eVTOL configuration and its rotors. Therefore, the objective of the present study is to clarify the flow physics and aerodynamic characteristics around the PPB-type eVTOL and its rotors through numerical simulations.

Reference URL

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Reasons and benefits of using JAXA Supercomputer System

We need to conduct the large-scale simulations on flow fields for new winged-eVTOL using "rFlow3D", "FaSTAR" and "FaSTAR-MOVE", which have been developed in JAXA.

Achievements of the Year

In the present year, the interaction between a high-lift device (Gurney flap) attached to the wing and the propeller flows installed above and below the wing was investigated for a newly proposed vector-thrust-type winged eVTOL aircraft. Based on the experimental conditions used in previous studies [1], the wing Reynolds number was set to 64,000, and the height of the Gurney flap was varied from 5% to 15% of the wing chord length. Numerical simulations were performed using the FaSTAR-MOVE solver. A moving overset grid method was applied to model the wing with the Gurney flap and the propellers located above and below the wing (Fig. 1).

Figure 2 shows the streamlines in a cross-sectional plane near the trailing edge of the wing for the case with a 5% Gurney flap height, comparing the conditions with and without propellers. The propeller flows above and below the wing significantly modify the flow field around the Gurney flap and in the wing wake. These results indicate that the aerodynamic characteristics of the wing with a Gurney flap are strongly influenced by the propeller flows.

In addition, the effects of propeller installation angle and the presence of the wing on propeller performance were investigated for the new vector-thrust-type winged eVTOL aircraft. The configurations analyzed include a single propeller, tandem propellers without a wing, and tandem propellers with a wing (PPB configuration). Numerical simulations were carried out using the rFlow3D solver. Figure 3 shows the flow fields obtained for each configuration. In the case of tandem propellers with a wing, the inflow velocity to the propellers is modified by the flow around the wing, resulting in performance differences between the upper and lower propellers.

Furthermore, the effect of applying a Gurney flap to a loop-type propeller [2], which has superior transonic characteristics, was investigated through numerical simulations using rFlow3D. Figure 4 shows the vortex structures and cross-sectional velocity distributions for the cases without a Gurney flap and with a 2% Gurney flap. The results demonstrate that the addition of the Gurney flap reduces flow separation near the blade tip and alters the strength of the tip vortex.

Fig.1: Flow field around new vector-thrust-type winged eVTOL

Fig.2: Effects of propeller flows installed upper and under wing on wing with Gurney flap

Fig.3: Flow fields around a single propeller, taandem propellers without wing, and taandem propellers with wing (PPB)

Fig.4: Effects of Gurney flap on loop-type propeller

Publications

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Usage of JSS

Computational Information

• Process Parallelization Methods: MPI
• Thread Parallelization Methods: N/A
• Number of Processes: 600
• Elapsed Time per Case: 336 Hour(s)

JSS3 Resources Used

Fraction of Usage in Total Resources*1(%): 0.08

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