JAXA Supercomputer System Annual Report February 2025-January 2026

Report Number: R25EACA61

Subject Category: JSS Inter-University Research

PDF (to be added)

• Responsible Representative: Kota Fukuda, Professor, Department of Aeronautics and Astronautics, Tokai University
• Contact Information: Kota Fukuda, Tokai University(kfukuda@tokai.ac.jp)
• Members: Kota Fukuda, Masato Ogawa

Abstract

When there is a flow path with a narrow diameter and temperature gradient in a gas-filled duct, acoustic vibration may occur thereby. This phenomenon is known as a thermoacoustic phenomenon, and the generated acoustic field may be accompanied by a unidirectional flow in the direction of the tube axis. While the magnitude of this flow is small compared to the vibration amplitude, it could give rise to a mass flow called acoustic mass streaming. Such acoustic mass flow influences the initially existing temperature distribution in the duct, causing convective heat transfer in addition to simple heat conduction and heat transport involved with acoustic vibrations. The heat transport phenomenon associated with this acoustic mass flow has a large effect on the heat transport characteristics of thermoacoustic devices, that is thermoacoustic prime mover, thermoacoustic refrigerator and so on. Therefore, in order to improve the performance of devices, it is inperative to clarify their characteristics. The goal of this study is to carry out numerical simulations using CFD to clarify the effects of thermoacoustic phenomena on acoustic mass flow and temperature distribution inside the duct, and ultimately on heat transport characteristics.

Reference URL

N/A

Reasons and benefits of using JAXA Supercomputer System

The numerical simulation in this study must be performed under an unsteady compressible flow environment, and especially the interaction between an unsteady acoustic field and heat transport is the key to this simulation. Therefore, although the mesh scale is relatively small, the simulation is necessarily highly accurate and long-time scale , minimum several seconds to tens of seconds on the heat transport time scale. In addition, building a database of analysis results requires a wide variety of calculation cases, resulting in a comprehensively large-scale and long-time simulation. In order to carry out simulations of this scale, it is essential to use a JAXA supercomputer that can run multiple simulations for long periods of time.

Achievements of the Year

Examination of the acoustic mass flow (Gedeon flow) generated in a thermoacoustic engine is an important issue in the development of thermoacoustic engines. In this study, numerical simulation of the flow in the thermoacoustic engine was performed in order to examine the effect of the acoustic mass flow (Gedeon flow). Fig.1 shows the simulation model. The working fluid was air at room temperature (1 atm, 293.15 K), and the temperature at the high-temperature heat exchanger was set as 457Kand 607K to compare with the results obtained by linear theory. Fig.2 shows the distribution of acoustic power. The results show that the tendency of CFD results and the results obtained by linear theory are similar and the discrepancy between the results of CFD and linear theory becomes big as the temperature at the high-temperature heat exchanger becomes high. Fig.3 shows the FFT analysis result for the CFD data. It is shown that some frequency peaks appear in the CFD result, even though only one peak appears in the results obtained by linear theory. Fig.4 shows the formation of vortices with respect to the time-averaged flow velocity. It is presumed that the generation of vortices makes high frequency peaks since these vortices cannot be considered in the linear theory. These relationships need to be examined in more detail in the future, including quantitative analysis.

Fig.1: Configuration of computational domain

Fig.2: Distribution of acoustic power

Fig.3: Result of FFT analysis

Fig.4: Comparison of streamline based on time-averaged velocity field

Publications

N/A

Usage of JSS

Computational Information

• Process Parallelization Methods: MPI
• Thread Parallelization Methods: OpenMP
• Number of Processes: 1 - 7
• Elapsed Time per Case: 700 Hour(s)

JSS3 Resources Used

Fraction of Usage in Total Resources*1(%): 0.00

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