JAXA Supercomputer System Annual Report (April 2018-March 2019)

Numerical Simulations of Fully Developed Turbulence
Report Number: R18EACA05
Subject Category: JSS2 Inter-University Research
URL: https://www.jss.jaxa.jp/en/ar/e2018/9089/
Responsible Representative
Susumu Goto, Professor, Osaka University
Contact Information
Susumu Goto (goto@me.es.osaka-u.ac.jp)
Members
Susumu Goto, Jun Kanki, Yutaro Motoori, Toru Kubo, Tomoyuki Kurita, Ryo Araki, Tsukasa Shinohara
Abstract
Flows in various systems appearing in the aerospace engineering are fully developed turbulence at high Reynolds
numbers. To numerically simulate these flows, we usually need to model small-scale motions in the flow. Suchturbulence models are on the basis of classical theories of small-scale statistics of turbulence. However, recent
laboratory experiments and numerical simulations showed that these classical theories did not necessarily hold
(Goto & Vassilicos 2015, 2016). The main aim of the present study is to reveal (un) universality of small-scalestatistics and physics behind it by means of direct numerical simulations of turbulence under various boundary
conditions.
Reasons for using JSS2Turbulent flows are one of the most important topics in the field of aerospace engineering. The direct numericalsimulations of fully developed turbulence require a massively parallel supercomputer with sufficient amount ofmemories and storages. These are the reasons to use JSS2.
Achievements of the YearIn this year, we revealed important knowledge on the sustaining mechanism of developed turbulence in a rotating
container. It is well-known that strong turbulence is sustained in a rotating container when its spin axis weakly
precesses. We have developed a numerical code with a flexible grid generation method to conduct simulations offlow in an arbitrary-shaped container. We have conducted simulations of turbulence in a precessing sphere,spheroids, and a cylinder and investigated the sustainability condition and mechanism of developed turbulence.
Irrespective of the container’s shape, strong turbulence is sustained when the precession is relatively weak, and it
is always accompanied by a pair of large-scale twisted vortices (Fig. 1).

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JAXA Special Publication JAXA-SP-19-003E

Fig. 1: Streamlines of the mean flow of developed turbulence sustained in aprecessing sphere. The direction of the velocity is from red to blue. Developed
turbulence driven by precession is, irrespective of the container’s shape,accompanied by a similar pair of large-scale vortices.

Publications- Peer-reviewed papers
1) K. Komoda and S. Goto, Three-dimensional flow structures of turbulence in precessing spheroids, Phys. Rev.
Fluids 4 (2019) 014603.
2) Y. Motoori and S. Goto, Generation mechanism of a hierarchy of vortices in a turbulent boundary layer, J.
Fluid Mech., 865 (2019) 1085-1109.
- Invited Presentations
1) S. Goto, Energy cascade in turbulence, Workshop on Fluid turbulence and Singularities of the Euler/NavierStokes equations, Harvard Univ. 13 March 2019.
- Oral Presentations
1) Y. Motoori and S. Goto, Hierarchy of vortices in wall-bounded turbulence, The 15th International Conferenceon Flow Dynamics.
2) S. Goto, Coherent structures in turbulence and their universality, International Conference on APEF 2018
(Advances in Physics of Emergent Orders in Fluctuations).
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JAXA Supercomputer System Annual Report (April 2018-March 2019)

Usage of JSS2

Computational Information
Process Parallelization Methods

MPI

Thread Parallelization Methods

Automatic Parallelization

Number of Processes

64 - 96

Elapsed Time per Case

35 Hour (s)Resources Used
Fraction of Usage in Total Resources*1 (%): 0.18
Details
Computational Resources
System Name

Amount of Core Time(core x hours)

Fraction of Usage*2 (%)

SORA-MA

1,205,735.81

0.15

SORA-PP

0.00

0.00

SORA-LM

0.00

0.00

SORA-TPP

0.00

0.00

File System Resources
File System Name

Storage Assigned (GiB)

Fraction of Usage*2 (%)/home561.71

0.58/data

64,048.80

1.13/ltmp

14,648.44

1.25

Archiver Resources
Archiver Name

Storage Used (TiB)

J-SPACE

Fraction of Usage*2 (%)
0.00

0.00

*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.

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