渡邉 智昭 (Tomoaki Watanabe)

2次元翼周りの定常流れの解析 （2022年7月版） OpenFOAMのインストールについては こちら 2次元翼周りの定常流れの解析をするチュートリアルを動かします。通常のOpenFOAMの使い方と同じですが、Windowsクロスコンパイラ版だとparaFoamが使えないため、可視化の手順だけ異なります。チュートリアルについては以下のサイトが参考になります。https://www.xsim.info/articles/OpenFOAM/Tutorials.html 可視化にはParaViewを使います。https://www.paraview.org/からダウンロードできます。 今回は非圧縮性流れの定常解析をするsimpleFoamを用います。 以下、 オレンジ背景の文字 はOpenFOAM上で入力するコマンドです。 1. OpenFOAMを起動する 2. チュートリアルのデータが保存されているディレクトリに移動 cd OpenFOAM/OpenFOAM-v2012/tutorials/  [Enter] ls  [Enter]       ファイル/ディレクトリ一覧を表示 チュートリアルのリストが表示される。各ディレクトリの中に解析手法の名前（**Foam）のディレクトリがあり、その中に様々な計算のチュートリアルが保存されている。ここでは、incompressible（非圧縮）内にあるsimpleFoam（非圧縮粘性流れの定常ソルバー）を使った2次元翼周りの流れのチュートリアルについて説明する。 3. チュートリアル用データを計算用ディレクトリRUNにコピー cp -r incompressible/simpleFoam/airFoil2D/ ~/RUN/   [Enter]      cp “A” “B” ： AをBにコピー       -r ：ディレクトリをコピーするためのオプション      ~/RUN ：起動時のディレクトリ”~/”の“RUN” 4. 計算用ディレクトリに移動して中身を確認 cd ~/RUN    [Enter] cd  airFoil2D   [Enter] 　チュートリアル用ディレクトリに移動 ls  [Enter]    中身の確認 5. 計算の実行（***Foam） simpleFoam [Enter]     

（2022年7月版） 書き間違いがあるかもしれないので鵜呑みにしないこと WindowsでOpenFOAM（https://www.openfoam.com/）を動かすための設定手順を紹介します。Windows Subsystem for Linux（WSL）を使ってUbuntu上でOpenFOAMを動かす方法もありますが、初めてLinuxを使う人には難しそうでした。今回はOpenFOAMのMinGWクロスコンパイル版を使います。手順通り進めればこれまでLinuxを使ったことがない人でもできるはずなので、授業の演習などでも使えると思います。 インストール環境：Windows 10、Windows 11 OpenFOAMのインストール 1. OpenFOAMのHPからMinGWクロスコンパイル版のインストーラをダウンロードする https://www.openfoam.com/download/openfoam-mingw-cross-compilation 2. ダウンロードしたファイル”OpenCFD-OpenFOAM-v2012-DP-mingw-crosscompiled-WindowsInstaller.exe”を 右クリック→管理者として実行 　 管理者として実行しないとOpenFOAMが動かない 3. インストーラの指示通り全てインストールする OpenFOAMの実行～初期設定 4. デスクトップにできたOpenFOAMのアイコンをダブルクリックして実行 インストールに問題がなければ以下のような画面が現れます ＊Linuxのコマンドで操作する cd “ディレクトリ名” [Enter] ：[ディレクトリ名]に移動 cd ..    [Enter] ：一つ上のディレクトリに移動 ls  [Enter] ：ファイル一覧を表示         pwd [Enter] ：現在のディレクトリを表示  　　など OpenFOAMのディレクトリとWindowsのフォルダを対応付ける OpenFOAMのディレクトリがWindowsでは使いづらいところにあるので、Cドライブ直下のフォルダからOpenFOAMのディレクトリを参照できるようにします。 以下、 オレンジ背景の文字 はOpenFOAM上で入力するコマンドです。 5

T. Watanabe, Y. Zheng, K. Nagata The decay of stably stratified grid turbulence in a viscosity-affected stratified flow regime Journal of Fluid Mechanics, 946 A29 2022 This article may be found at  https://doi.org/10.1017/jfm.2022.617 . Read only version is freely available  here . Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  Abstract The decay of stably stratified turbulence generated by a towed rake of vertical plates is investigated by direct numerical simulations (DNS) of temporally evolving grid turbulence in a linearly stratified fluid. The Reynolds number ReM=U0M/ν is 5000 or 10 000 while the Froude number FrM=U0/MN is between 0.1 and 6 (U0: towing speed; M: mesh size; ν: kinematic viscosity; N: Brunt–Väisälä frequency). The DNS results are compared with the theory of stably stratified axisymmetric Saffman turbulence. Here, the theory is extended to a viscosity-affected stratified flow regime with low b

K. Inokuma, T. Maeda, T. Watanabe, K. Nagata Diaphragmless shock tube with multiple air-operated valves Experiments in Fluids, 63 121 2022 This article may be found at  https://doi.org/10.1007/s00348-022-03473-y  or on ResearchGate . Accepted manuscript is available here.  This version is free to view and download for private research and study only.  Abstract In this study, a novel diaphragmless shock tube driven by a driver valve system consisting of multiple air-operated valves was developed. The novel shock tube can generate shock waves with high repeatability, which are required for statistical investigations of shock waves. The main valve of the driver valve system is opened by decompressing the air in the sub-high-pressure room behind the main valve using “sub-valves”; this results in a shock wave formation inside the shock tube. Three different driver valves (driver valve with “a single solenoid sub-valve,” “a single air-operated sub valve,” and “three air-operated sub-valves”)

T. Akao, T. Watanabe, K. Nagata Vertical confinement effects on a fully developed turbulent shear layer Physics of Fluids, 34 055129 2022 This article may be found at  https://doi.org/10.1063/5.0090686 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  Abstract The effects of vertical confinement on a turbulent shear layer are investigated with large-eddy simulations of a freely developing shear layer (FSL) and a wall-confined shear layer (WSL) that develops between two horizontal walls. In the case of the WSL, the growth of the shear layer is inhibited by the walls. Once the walls prevent the development of the shear layer, highly anisotropic velocity fluctuations become prominent in the flow. These anisotropic velocity fluctuations are recognized as elongated large-scale structures (ELSS), whose streamwise length is much larger than the length scales in the other direc

K. Yamamoto, T. Ishida, T. Watanabe, K. Nagata Experimental and numerical investigation of compressibility effects on velocity derivative flatness in turbulence Physics of Fluids, 34 055101 2022 This article may be found at  https://doi.org/10.1063/5.0085423 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  Abstract Compressibility effects on the velocity derivative flatness 𝐹∂𝑢′/∂𝑥 are investigated by experiments with opposing arrays of piston-driven synthetic jet actuators (PSJAs) and direct numerical simulations (DNS) of statistically steady compressible isotropic turbulence and temporally evolving turbulent planar jets with subsonic or supersonic jet velocities. Experiments using particle image velocimetry show that nearly homogeneous isotropic turbulence is generated at the center of a closed box from interactions between supersonic synthetic jets. The dependenc

K. Yamamoto, T. Watanabe, K. Nagata Turbulence generated by an array of opposed piston-driven synthetic jet actuators Experiments in Fluids, 63 35 2022 This article may be found at  https://doi.org/10.1007/s00348-021-03351-z . Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  Abstract This paper investigates turbulence generated by an array of opposed piston-driven synthetic jet actuators in a closed chamber. Each actuator intermittently generates supersonic jets with four orifice holes, and the interaction of 32 supersonic jets produces turbulence. Velocity measurement is conducted with particle image velocimetry using oil mist as the tracer particles, which are internally generated by the synthetic jet actuators. The turbulence with a small mean velocity is generated at the central region of the chamber, where the root-mean-square (rms) velocity fluctuations are also almost uniform in space. The rms velocity fluc

Y. Zheng, K. Nagata, T. Watanabe Turbulent characteristics and energy transfer in the far field of active-grid turbulence Physics of Fluids, 33 115119 2021 The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  This article may be found at  https://doi.org/10.1063/5.0070912 . Abstract Turbulent characteristics in the far field of active-grid turbulence have been investigated through wind tunnel experiments using hot-wire anemometry. Two forcing protocols are employed following previous studies: one is the double-random mode and the other is the open mode with the grid remaining static with minimum blockage. The integral length scale L for the double-random modes slightly decreases with streamwise distance in the far field as observed in the near field of the active-grid turbulence. The nondimensional dissipation rate 𝐶𝜀 for the double-random modes is around 0.5. This asympto

T. Watanabe, K. Nagata Large-scale characteristics of a stably stratified turbulent shear layer Journal of Fluid Mechanics, 927 A27 2021 This article may be found at  https://doi.org/10.1017/jfm.2021.773 . Read only version is freely available  here . Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  Abstract Implicit large eddy simulation is performed to investigate large-scale characteristics of a temporally evolving, stably stratified turbulent shear layer arising from the Kelvin–Helmholtz instability. The shear layer at late time has two energy-containing length scales: the scale of the shear layer thickness, which characterizes large-scale motions (LSM) of the shear layer; and the larger streamwise scale of elongated large-scale structures (ELSS), which increases with time. The ELSS forms in the middle of the shear layer when the Richardson number is sufficiently large. The contribution of the ELSS to velocity

T. Watanabe, K. Tanaka, K. Nagata Solenoidal linear forcing for compressible, statistically steady, homogeneous isotropic turbulence with reduced turbulent Mach number oscillation Physics of Fluids, 33 095108 2021 This article may be found at  https://doi.org/10.1063/5.0062596 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  Abstract This study investigates a solenoidal linear forcing scheme with reduced oscillation of a turbulent Mach number MT for direct numerical simulations (DNS) of statistically steady, homogeneous isotropic turbulence. A conventional linear forcing scheme results in a large temporal oscillation of MT, where the maximum MT reaches about 1.1 times the time-averaged MT. Therefore, strong shocklets are generated when MT becomes large although such strong shocklets hardly appear when MT is close to the time-averaged value. DNS with the proposed forcin

K. Inokuma,T. Watanabe, K. Nagata, Y. Sakai Experimental study on shock wave modulation caused by velocity and temperature fluctuations in-cylinder wake Physical Review Fluids, 6 063401 2021 This article may be found at  https://doi.org/10.1103/PhysRevFluids.6.063401 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and APS.  Abstract Experiments on a spherical shock wave propagating across an unheated- or a heated-cylinder wake are performed in a wind tunnel to investigate the effects of velocity and temperature fluctuations of turbulence on the shock wave. The temperature of the heated cylinder is low enough for the buoyancy effect to be negligible in the wake development, and comparisons between the heated- and unheated-cylinder experiments highlight the effects of temperature fluctuations on the shock wave. Peak overpressure of the spherical shock wave is measured on a wall after the sh

M. Hayashi, T. Watanabe, K. Nagata Characteristics of small-scale shear layers in a temporally evolving turbulent planer jet Journal of Fluid Mechanics, 920 A38 2021 This article may be found at  https://doi.org/10.1017/jfm.2021.459 . Read only version is freely available  here . Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  Abstract Characteristics of small-scale shear layers are studied with direct numerical simulations of a temporally evolving turbulent planar jet. The shear layers that internally exist in turbulence are detected with a tensor of shearing motion, which is extracted from a velocity gradient tensor with a triple decomposition. Flow visualization of the shear intensity confirms the existence of layer structures with intense shear. The mean flow characteristics around local maxima of the shear intensity are investigated with averages taken in the shear coordinate system, which is defined based o

T. Katagiri, T. Watanabe, K. Nagata Statistical properties of a model of a turbulent patch arising from a breaking internal wave Physics of Fluids, 33 055107 2021 This article may be found at  https://doi.org/10.1063/5.0046832 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  Abstract The turbulent patch arising from internal gravity wave breaking is investigated with direct numerical simulation of a stably stratified flow over a two-dimensional hill. The turbulent patch is distinguished from the non-turbulent wave region with potential vorticity. The turbulent patch is highly intermittent, and its location fluctuates with space and time. The buoyancy Reynolds number slowly decays with time in the turbulent patch and the mixing efficiency stays around 0.2. The turbulent patch is separated from the non-turbulent wave region by a turbulent/non-turbulent interfacial (TNTI)

M. Hayashi, T. Watanabe, K. Nagata The relation between shearing motions and the turbulent/non-turbulent interface in a turbulent planar jet Physics of Fluids, 33 055126 2021 This article may be found at  https://doi.org/10.1063/5.0045376 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  Abstract The relation between shearing motions and the turbulent/non-turbulent interfacial (TNTI) layer is studied with direct numerical simulation of a temporally evolving planar jet. Small-scale shear layers are detected with the triple decomposition of the velocity gradient tensor, which is decomposed into shear, rotation, and elongation tensors. The shear layers are found in the turbulent sublayer more frequently than in the turbulent core region although they hardly appear in the viscous superlayer. The shear layers undergo a biaxial strain with stretching in the shear vorticity di

Y. Zheng, K. Nagata, T. Watanabe Energy dissipation and enstrophy production/destruction at very low Reynolds numbers in the final stage of the transition period of decay in grid turbulence Physics of Fluids, 33 035147 2021 This article may be found at  https://doi.org/10.1063/5.0041929 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  Abstract Decay characteristics of turbulent kinetic energy and enstrophy in grid turbulence have been investigated in the far downstream region (x/M∼10^3: x is the downstream distance from the grid, M is the mesh size of the grid) through wind tunnel experiments using hot-wire anemometry, with the lowest turbulent Reynolds number Reλ≈5. The non-dimensional dissipation rate Cε increases rapidly toward the final stage of the transition period of decay and the profile agrees well with previous direct numerical simulation [W. D. McComb et al.

Y. Tai, T. Watanabe, K. Nagata Multi-particle models of molecular diffusion for Lagrangian simulation coupled with LES for passive scalar mixing in compressible turbulence Computers and Fluids, 221 104886 2021 This article may be found at  https://doi.org/10.1016/j.compfluid.2021.104886 . Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  Abstract Lagrangian simulation coupled with large eddy simulation (LES) is studied for turbulent scalar mixing in compressible flows, where Lagrangian simulation solves advection-diffusion equations with computational particles. In Lagrangian simulation, a molecular diffusion term needs to be modeled with a so-called mixing model, which also requires modeling the dissipation rate of scalar fluctuations. The present study extends a particle-based subgrid-scale model for the scalar dissipation rate to compressible flows, and its validity in compressible turbulence is examined with di

Y. Tai, T. Watanabe, K. Nagata Implicit large eddy simulation of passive scalar transfer in compressible planar jet International Journal for Numerical Methods in Fluids, 93 1183-1198 2021 Accepted manuscript is available  here .  This is the accepted version of the article, which has been published in final form at  https://doi.org/10.1002/fld.4924 . This article may be used for non-commercial purposes in accordance with the Wiley Self-Archiving Policy  [http://www.wileyauthors.com/self-archiving]. Abstract Implicit large eddy simulation (ILES) of passive scalar transfer in compressible turbulence is evaluated for subsonic and supersonic turbulent planar jets. The ILES used in this study relies on fully explicit numerical schemes for spatial and temporal discretization and low-pass and shock-capturing filters used as an implicit subgrid-scale (SGS) model. The ILES results are compared with the direct numerical simulation (DNS) database of the same flows. The ILES results exhibit good

T. Matsushima, K. Nagata, T. Watanabe Wavelet analysis of shearless turbulent mixing layer Physics of Fluids, 33 025109 2021 This article may be found at  https://doi.org/10.1063/5.0038132 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  Abstract The intermittency and scaling exponents of structure functions are experimentally studied in a shearless turbulent mixing layer. Motivated by previous studies on the anomalous scaling in homogeneous/inhomogeneous turbulent flows, this study aims to investigate the effect of strong intermittency caused by turbulent kinetic energy diffusion without energy production by mean shear. We applied an orthonormal wavelet transformation to time series data of streamwise velocity fluctuations measured by hot-wire anemometry. Intermittent fluctuations are extracted by a conditional method with the local intermittency measure, and the scal

T. Watanabe, C. B, da Silva, K. Nagata Scale-by-scale kinetic energy budget near the turbulent/non-turbulent interface Physical Review Fluids, 5 124610 2020 This article may be found at  https://doi.org/10.1103/PhysRevFluids.5.124610 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and APS.  Abstract A scale-by-scale kinetic energy budget is analyzed near the turbulent/nonturbulent interfacial (TNTI) layer with direct numerical simulations (DNSs) of a local turbulent front evolving without mean shear (shear-free turbulence). A local volume average is used to decompose the flow variables into their large-scale and small-scale components near the TNTI layer. The kinetic energy and interscale energy flux from large to small scales of motion are shown to be severely depleted for small scales within the viscous superlayer. The forward interscale energy transfer from large to small scales near t

K. Tanaka, T. Watanabe, K. Nagata Statistical analysis of deformation of a shock wave propagating in a local turbulent region Physics of Fluids, 32 096107 2020 This article may be found at  https://doi.org/10.1063/5.0019784 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  Abstract Direct numerical simulation is performed for analyzing the interaction between a normal shock wave and turbulence. The shock wave is initially located in a quiescent fluid and propagates into a local turbulent region. This flow setup allows investigation of the initial transition and statistically steady stages of the interaction. Shock deformation is quantified using the local shock wave position. The root-mean-square (rms) fluctuation in the shock wave position increases during the initial stage of the interaction, for which the time interval divided by the integral time scale increases wit

T. Watanabe, K. Tanaka, K. Nagata Characteristics of shearing motions in incompressible isotropic turbulence Physical Review Fluids, 5 072601(R) 2020 This article may be found at  https://doi.org/10.1103/PhysRevFluids.5.072601 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and APS.  Abstract Regions with shearing motions are investigated in isotropic turbulence with the triple decomposition, by which a velocity gradient tensor is decomposed into three components representing an irrotational straining motion, a rotating motion, and a shearing motion. A mean flow around the shearing motions shows that a thin shear layer is sustained by a biaxial strain, which is consistent with Burgers' vortex layer. The thickness of each shear layer is well predicted by Burgers' vortex layer. A comparison between genuine turbulence and a random velocity field confirms that the biaxial strain actin

K. Aruga, T. Watanabe, K. Nagata Color contamination correction based on light intensity correlation in two-color, double-exposure particle tracking velocimetry Experiments in Fluids, 61 142 2020 This article may be found at  https://doi.org/10.1007/s00348-020-02964-0 . Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  Abstract An algorithm for correcting color contamination is proposed for two-color, double-exposure particle tracking velocimetry (PTV). A two-color PTV system used in this study consists of blue and green laser diodes and a consumer digital camera, where a laser pulser with an avalanche transistor is developed for achieving optical pulses of 50 ns for application in airflows. In the PTV, the camera captures images of tracer particles illuminated by a sequence of green and blue light pulses with a certain time interval. Because of spectral characteristics of a Bayer filter, camera sensors in a blue c

K. Aruga, K. Inokuma, T. Watanabe, K. Nagata, Y. Sakai Experimental investigation of interactions between turbulent cylinder wake and spherical shock wave Physics of Fluids, 32 16101 2020 This article may be found at  https://doi.org/10.1063/1.5128267 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  Abstract Interactions between a spherical shock wave and a turbulent cylinder wake are studied with wind tunnel experiments. The shock wave is generated outside the wake and propagates across the turbulent wake. Instantaneous streamwise velocity is measured on the wake centerline while peak overpressure of the shock wave is measured outside the wake after the shock wave has passed across the wake. The experiments are performed for various conditions of the cylinder wake to investigate the influences of the root-mean-squared (rms) velocity fluctuation and of the length of th

R. Nagata, T. Watanabe, K. Nagata, C. B. da Silva Triple decomposition of velocity gradient tensor in homogeneous isotropic turbulence Computer & Fluids, 198 104389 2020 This article may be found at  https://doi.org/10.1016/j.compfluid.2019.104389 . Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  Abstract The triple decomposition of a velocity gradient tensor is studied with direct numerical simulations of homogeneous isotropic turbulence, where the velocity gradient tensor $\nabla {\bd{u}}$ is decomposed into three components representing an irrotational straining motion $(\nabla\bd{u})_{\rm EL}$, a rigid-body rotation $(\nabla\bd{u})_{\rm RR}$, and a shearing motion  $(\nabla\bd{u})_{\rm SH}$. Strength of these motions can be quantified with the decomposed components. A procedure of the triple decomposition is proposed for three-dimensional flows, where the decomposition is applied in a basic reference fram

T. Watanabe, X. Zhang, K. Nagata Direct numerical simulation of incompressible turbulent boundary layers and planar jets at high Reynolds numbers initialized with implicit large eddy simulation Computer & Fluids, 194 104314 2019 This article may be found at  https://doi.org/10.1016/j.compfluid.2019.104314 . Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  Abstract A direct numerical simulation (DNS) initialized with an implicit large eddy simulation (ILES) is performed for temporally evolving planar jets and turbulent boundary layers. In the ILES, an initial laminar flow develops into a fully developed state of the planar jet or the boundary layer. Subsequently, the DNS is started from the flow field obtained by the ILES. This hybrid ILES/DNS methodology is tested for the planar jet and boundary layer by comparing the results with full DNS started from the initial laminar flow. The ILES results used as the i

T. Watanabe, J. J. Riley, K. Nagata, K. Matsuda, R. Onishi Hairpin vortices and highly elongated flow structures in a stably-stratified shear layer Journal of Fluid Mechanics, 878 37-61 2019 This article may be found at  https://doi.org/10.1017/jfm.2019.577 . Read only version is freely available  here . Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  Abstract Turbulent structures in stably stratified shear layers are studied with direct numerical simulation. Flow visualization confirms the existence of hairpin vortices and highly elongated structures with positive and negative velocity fluctuations, whose streamwise lengths divided by the layer thickness are O(10^0) and O(10^1), respectively. The flow at the wavelength related to these structures makes a large contribution to turbulent kinetic energy. These structures become prominent in late time, but with small buoyancy Reynolds numbers indicating suppression

K. Inokuma, T. Watanabe, K. Nagata, Y. Sakai Statistics of overpressure fluctuations behind a weak shock wave interacting with turbulence Physics of Fluids, 31 085119 2019 This article may be found at  https://doi.org/10.1063/1.5110185 . The PDF is also available  here .    This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.  Abstract The overpressure fluctuations behind a weak shock wave interacting with turbulence are studied by wind tunnel experiments, where a spherical shock wave propagates in grid turbulence. The experiments are conducted for various values of the shock Mach number MS0 of the shock wave and turbulent Mach number MT of the grid turbulence. The experimental results show that the root-mean-squared peak-overpressure fluctuation divided by the averaged peak-overpressure, σΔp/⟨Δp⟩, where the inherent noise caused by the experimental facility is removed, follows a power law of MT^2/(MS0^2−1). The

T. Watanabe, C. B. da Silva, K. Nagata Non-dimensional energy dissipation rate near the turbulent/non-turbulent interfacial layer in free shear flows and shear free turbulence Journal of Fluid Mechanics, 875 321-344 2019 This article may be found at  https://doi.org/10.1017/jfm.2019.462 . Read only version is freely available  here . Accepted manuscript is available  here .  This version is free to view and download for private research and study only.  Abstract The non-dimensional dissipation rate Cε=εL/u′3, where ε, L and u′ are the viscous energy dissipation rate, integral length scale of turbulence and root-mean-square of the velocity fluctuations, respectively, is computed and analysed within the turbulent/non-turbulent interfacial (TNTI) layer using direct numerical simulations of a planar jet, mixing layer and shear free turbulence. The TNTI layer that separates the turbulent and non-turbulent regions exists at the edge of free shear turbulent flows and turbulent boundary laye