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Statistics of local Reynolds number in box turbulence: ratio of inertial to viscous forces

https://nied-repo.bosai.go.jp/records/6379

Item type

researchmap(1)

公開日

2023-09-20

タイトル

言語

タイトル

Statistics of local Reynolds number in box turbulence: ratio of inertial to viscous forces

タイトル

言語

タイトル

Statistics of local Reynolds number in box turbulence: ratio of inertial to viscous forces

言語

eng

著者

Atsuya Uno

抄録

内容記述タイプ

Other

内容記述

In high-Reynolds-number turbulence the spatial distribution of velocity fluctuation at small scales is strongly non-uniform. In accordance with the non-uniformity, the distributions of the inertial and viscous forces are also non-uniform. According to direct numerical simulation (DNS) of forced turbulence of an incompressible fluid obeying the Navier?Stokes equation in a periodic box at the Taylor microscale Reynolds number

$R_\lambda \approx 1100$

, the average

$\langle R_{loc}\rangle$

over the space of the ‘local Reynolds number’

$R_ {loc}$

, which is defined as the ratio of inertial to viscous forces at each point in the flow, is much smaller than the conventional ‘Reynolds number’ given by

$Re \equiv UL/\nu$

, where

$U$

and

$L$

are the characteristic velocity and length of the energy-containing eddies, and

$\nu$

is the kinematic viscosity. While both conditional averages of the inertial and viscous forces for a given squared vorticity

$\omega ^{2}$

increase with

$\omega ^{2}$

at large

$\omega ^{2}$

, the conditional average of

$R_ {loc}$

is almost independent of

$\omega ^{2}$

. A comparison of the DNS field with a random structureless velocity field suggests that the increase in the conditional average of

$R_ {loc}$

with

$\omega ^{2}$

at large

$\omega ^{2}$

is suppressed by the Navier?Stokes dynamics. Something similar is also true for the conditional averages for a given local energy dissipation rate per unit mass. Certain features of intermittency effects such as that on the

$Re$

dependence of

$\langle R_{loc}\rangle$

are explained by a multi-fractal model by Dubrulle (J. Fluid Mech., vol. 867, 2019, P1).

言語

抄録

内容記述タイプ

Other

内容記述

In high-Reynolds-number turbulence the spatial distribution of velocity fluctuation at small scales is strongly non-uniform. In accordance with the non-uniformity, the distributions of the inertial and viscous forces are also non-uniform. According to direct numerical simulation (DNS) of forced turbulence of an incompressible fluid obeying the Navier-Stokes equation in a periodic box at the Taylor microscale Reynolds number R-lambda approximate to 1100, the average < R-loc > over the space of the 'local Reynolds number' R-loc, which is defined as the ratio of inertial to viscous forces at each point in the flow, is much smaller than the conventional 'Reynolds number' given by Re = UL/v, where U and L are the characteristic velocity and length of the energy-containing eddies, and nu is the kinematic viscosity. While both conditional averages of the inertial and viscous forces for a given squared vorticity omega(2) increase with omega(2) at large omega(2), the conditional average of R-loc is almost independent of omega(2). A comparison of the DNS field with a random structureless velocity field suggests that the increase in the conditional average of R-loc with omega(2) at large omega(2) is suppressed by the Navier-Stokes dynamics. Something similar is also true for the conditional averages for a given local energy dissipation rate per unit mass. Certain features of intermittency effects such as that on the Re dependence of < R-loc > are explained by a multi-fractal model by Dubrulle (J. Fluid Mech., vol. 867, 2019, P1).

言語

書誌情報

ja : Journal of Fluid Mechanics
en : JOURNAL OF FLUID MECHANICS

巻 929, 発行日 2021-10-25

出版者

言語

出版者

Cambridge University Press (CUP)

出版者

言語

出版者

CAMBRIDGE UNIV PRESS

ISSN

収録物識別子タイプ

EISSN

収録物識別子

1469-7645

DOI

Versions

Ver.1

2023-09-20 08:09:48.766157

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インデックスリンク

インデックスツリー

アイテム

Statistics of local Reynolds number in box turbulence: ratio of inertial to viscous forces

× Yukio Kaneda

× Takashi Ishihara

× Koji Morishita

× Mitsuo Yokokawa

× Atsuya Uno

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