JAXA Supercomputer System Annual Report February 2025-January 2026

Report Number: R25EACA55

Subject Category: JSS Inter-University Research

PDF (to be added)

• Responsible Representative: Takayuki Nagata, Assistant Professor, Nagoya University
• Contact Information: Takayuki Nagata (Assistant Professor at Nagoya University)(nagata.takayuki.x7@f.mail.nagoya-u.ac.jp)
• Members: Taku Nonomura, Takayuki Nagata, Shunta Takahashi

Abstract

This study focuses on compressible multiphase flows and investigates particle-laden flows and flows around small particles through direct numerical simulation of the Navier–Stokes equations. The objective is to acquire fundamental knowledge for understanding high-speed particle-laden flow phenomena, such as those observed in rocket-engine exhaust jets. Specifically, the study addresses hydrodynamic interaction effects among particles in subsonic to supersonic flows, as well as interactions of particles with shock waves and turbulence. The lift, drag, and moment acting on the particles will be quantified, and the associated flow phenomena will be elucidated using detailed flow-field information, including velocity and pressure distributions. The target flow fields considered in this study correspond to conditions in which particles are convected in high-speed flows and traverse shock waves, turbulence, and shear layers. In addition to the insights previously obtained by the applicant on high-speed flow around a single particle in a uniform flow, this study will clarify inter-particle hydrodynamic interactions and the influence of particles on the global flow structure, such as the modulation of shock waves and turbulence. These efforts will contribute to the development of a database for high-fidelity modeling of compressible multiphase flows.

Reference URL

N/A

Reasons and benefits of using JAXA Supercomputer System

In the present study, a parametric study by direct numerical simuation of the Navier-Stokes equations is conducted, and thus, a large-scale parallel calculation is required.

Achievements of the Year

The effects of particle temperature and Mach number on the drag coefficient during the shock–particle interaction process were investigated by direct numerical simulations of the three-dimensional compressible Navier–Stokes equations. Both three-dimensional and axisymmetric simulations were performed. The particle Reynolds number was set to 300 and 200, while the particle Mach number and particle temperature were varied. Either isothermal or adiabatic boundary conditions were imposed on the particle surface. The rapid increase in the drag coefficient induced by interaction with the shock wave (Fig. 1) was evaluated in terms of impulse, and the effects of particle temperature and particle Mach number on the drag coefficient were clarified under various conditions (Fig. 2). The pressure component becomes dominant at low Mach numbers, whereas the viscous component increases in the high-subsonic regime, resulting in two peak regions in the total drag response. These peaks are particularly pronounced at low temperature ratios, that is, when the particle surface temperature is lower than the temperature behind the shock wave. The obtained drag increment can be added to the drag coefficient estimated from a steady drag model, making it applicable to compressible multiphase-flow simulations.

In addition, toward the development of a numerical method for gas–solid multiphase flows based on data-driven reduced-order modeling, a database was constructed and preliminary calculations were carried out.

Fig.1: Representative snapshots of the streamwise velocity field and time histories of the drag coefficient.

Fig.2: Effects of Mach number and temperature ratio on the ratio of the shock-induced impulse increment to the impulse due to steady-state drag.

Publications

- Oral Presentations

Takahashi, S., Nagata, T., and Nonomura, T., "Particle temperature and Mach number effects on drag coefficient in shock-particle interaction," APS Division of Fluid Dynamics Annual Meeting 2025, Houston, USA (2025).

Usage of JSS

Computational Information

• Process Parallelization Methods: MPI
• Thread Parallelization Methods: OpenMP
• Number of Processes: 1 - 2
• Elapsed Time per Case: 50 Hour(s)

JSS3 Resources Used

Fraction of Usage in Total Resources*1(%): 0.07

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