Hostname: page-component-857557d7f7-d5hhr Total loading time: 0 Render date: 2025-11-20T06:09:59.165Z Has data issue: false hasContentIssue false
  • English
  • Français

Investigation of the turbulent/non-turbulent interface in separated and reattaching flows

Published online by Cambridge University Press:  20 November 2025

Sicheng Li Open the ORCID record for Sicheng Li [Opens in a new window]  and
Jinjun Wang Open the ORCID record for Jinjun Wang [Opens in a new window]
Sicheng Li
Affiliation:
Fluid Mechanics Key Laboratory of Education Ministry, Beihang University , Beijing 100191, PR China
Jinjun Wang*
Affiliation:
Fluid Mechanics Key Laboratory of Education Ministry, Beihang University , Beijing 100191, PR China
*
Corresponding author: Jinjun Wang, jjwang@buaa.edu.cn
Get access Rights & Permissions [Opens in a new window]

Abstract

Characteristics of the turbulent/non-turbulent interface (TNTI) and entrainment in separated and reattaching flows induced by an oscillating fence are investigated using time-resolved particle image velocimetry. Disturbed flows are classified into subcritical, transitional, critical and supercritical cases based on the ratio of the oscillation frequency to the natural vortex shedding frequency. In the recirculation zone, distinct vortices across different cases lead to significant variations in TNTI characteristics. In the subcritical case, the TNTI evolution resembles that in the stationary fence case but with intensified height fluctuations due to the undulation of separated shear layer. For other cases, the mean TNTI height increases with the oscillation frequency, while height fluctuation diminishes. The TNTI thickness varies with nearby vortices, scaling with the Taylor microscale. After the reattachment, TNTI height distributions converge into two groups: subcritical and transitional cases exhibit larger fluctuations and positively skewed probability density functions (PDFs), while critical and supercritical cases show smaller fluctuations and basically symmetric PDFs. The TNTI thickness becomes consistent across various cases, matching the adjacent small-scale vortex size. Besides, the nibbling mechanism of entrainment aligns well with the flow development. The minimum mean entrainment velocity coincides with the strongest prograde vortex while the maximum occurs at $x\approx 1.2x_{{r}}$ (where $x$ denotes the streamwise coordinate and $x_{{r}}$ is the mean reattachment position) in all cases. Engulfment is enhanced near the reattachment location by oscillations in the transitional and critical cases, but is suppressed in the supercritical cases due to the weakness of vortex structures at higher oscillation frequencies.

JFM classification

Boundary Layers: Boundary layer separation Turbulent Flows: Intermittency Mixing: Turbulent mixing

Information

Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 1023 , 25 November 2025 , A21
Check for updates
Copyright
© The Author(s), 2025. Published by Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Article purchase

Temporarily unavailable

References

Agelinchaab, M. & Tachie, M.F. 2008 PIV study of separated and reattached open channel flow over surface mounted blocks. J. Fluid Engng 130 (6), 061206.10.1115/1.2911677CrossRefGoogle Scholar
Balamurugan, G., Rodda, A., Philip, J. & Mandal, A. 2020 Characteristics of the turbulent non-turbulent interface in a spatially evolving turbulent mixing layer. J. Fluid Mech. 894, A4.10.1017/jfm.2020.241CrossRefGoogle Scholar
Bisset, D.K., Hunt, J.C.R. & Rogers, M.M. 2002 The turbulent/non-turbulent interface bounding a far wake. J. Fluid Mech. 451, 383–410.10.1017/S0022112001006759CrossRefGoogle Scholar
Borrell, G. & Jiménez., J. 2016 Properties of the turbulent/non-turbulent interface in boundary layers. J. Fluid Mech. 801, 554.10.1017/jfm.2016.430CrossRefGoogle Scholar
Breda, M. & Buxton, O.R.H. 2019 Behaviour of small-scale turbulence in the turbulent/non-turbulent interface region of developing turbulent jets. J. Fluid Mech. 879, 187–216.10.1017/jfm.2019.676CrossRefGoogle Scholar
Brown, G.L. & Roshko, A. 1974 On density effects and large structure in turbulent mixing layers. J. Fluid Mech. 64 (4), 775–816.10.1017/S002211207400190XCrossRefGoogle Scholar
Chauhan, K., Philip, J. & Marusic, I. 2014 a Scaling of the turbulent/non-turbulent interface in boundary layers. J. Fluid Mech. 751, 298–328.10.1017/jfm.2014.298CrossRefGoogle Scholar
Chauhan, K., Philip, J., de Silva, C.M., Hutchins, N. & Marusic, I. 2014 b The turbulent/non-turbulent interface and entrainment in a boundary layer. J. Fluid Mech. 742, 119–151.10.1017/jfm.2013.641CrossRefGoogle Scholar
Cheng, Y. & Chen, Q. 2021 Large eddy simulation and dynamic mode decomposition of turbulent mixing layers. Appl. Sci. 11 (24), 12127.10.3390/app112412127CrossRefGoogle Scholar
Cui, G., Pan, C., Wu, D., Ye, Q. & Wang, J. 2019 Effect of drag reducing riblet surface on coherent structure in turbulent boundary layer. Chinese J. Aeronaut. 32 (11), 2433–2442.10.1016/j.cja.2019.04.023CrossRefGoogle Scholar
Fang, X. & Tachie, M.F. 2019 On the unsteady characteristics of turbulent separations over a forward-backward-facing step. J. Fluid Mech. 863, 994–1030.10.1017/jfm.2018.962CrossRefGoogle Scholar
Fang, X., Tachie, M.F. & Dow, K. 2022 Turbulent separations beneath semi-submerged bluff bodies with smooth and rough undersurfaces. J. Fluid Mech. 947, A19.10.1017/jfm.2022.661CrossRefGoogle Scholar
George, W.K. & Hussein, H.J. 1991 Locally axisymmetric turbulence. J. Fluid Mech. 233, 1–23.10.1017/S0022112091000368CrossRefGoogle Scholar
Hind, M., Lindberg, W. & Naughton, J. 2008 Quantification of flow structures generated by an oscillating fence in a flat plate laminar boundary layer. In 46th AIAA Aerospace Sciences Meeting and Exhibit, pp. 2008–2600.Google Scholar
Huang, J., Burridge, H.C. & van Reeuwijk, M. 2023 Local entrainment across a tnti and a tti in a turbulent forced fountain. J. Fluid Mech. 977, A13.10.1017/jfm.2023.947CrossRefGoogle Scholar
Jahanbakhshi, R. & Madnia, C. 2016 Entrainment in a compressible turbulent shear layer. J. Fluid Mech. 797, 564–603.10.1017/jfm.2016.296CrossRefGoogle Scholar
Kankanwadi, K.S. & Buxton, O.R.H. 2020 Turbulent entrainment into a cylinder wake from a turbulent background. J. Fluid Mech. 905, A35.10.1017/jfm.2020.755CrossRefGoogle Scholar
Lee, J., Sung, H.J. & Zaki, T.A. 2017 Signature of large-scale motions on turbulent/non-turbulent interface in boundary layers. J. Fluid Mech. 819, 165–187.10.1017/jfm.2017.170CrossRefGoogle Scholar
Li, B., Yang, Z., Zhang, X., He, G., Deng, B.-Q. & Shen, L. 2020 Using machine learning to detect the turbulent region in flow past a circular cylinder. J. Fluid Mech. 905, A10.10.1017/jfm.2020.725CrossRefGoogle Scholar
Li, S., Long, Y. & Wang, J. 2022 Turbulent/non-turbulent interface for laminar boundary flow over a wall-mounted fence. Phys. Fluids 34, 125113.10.1063/5.0128609CrossRefGoogle Scholar
Li, S. & Wang, J. 2024 Entrainment of the shear layer separated from a wall-mounted fence. J. Fluid Mech. 999, A6.10.1017/jfm.2024.685CrossRefGoogle Scholar
Li, Sicheng & Wang, Jinjun 2025 Frequency effect on properties of turbulent/non-turbulent interface in separated and reattaching flows past an oscillating fence, In Proceedings of the IUTAM Symposium on Turbulent/Non-Turbulent Interface in Turbulent Shear Flows, (ed. Jinjun Wang & Ivan Marusic), 990 pp. 182–193. Cham: Springer Nature.10.1007/978-3-031-78151-3_14CrossRefGoogle Scholar
Long, Y., Wang, J. & Pan, C. 2022 a Universal modulations of large-scale motions on entrainment of turbulent boundary layers. J. Fluid Mech. 941, A68.10.1017/jfm.2022.355CrossRefGoogle Scholar
Long, Y., Wang, J. & Wang, J. 2022 b ‘Turbulent/non-turbulent interface’ in a low-Reynolds-number transitional boundary layer over a multi-element airfoil. Phys. Fluids 34, 102111.10.1063/5.0120934CrossRefGoogle Scholar
Mathew, J. & Basu, A.J. 2002 Some characteristics of entrainment at a cylindrical turbulence boundary. Phys. Fluids 14, 2065–2072.10.1063/1.1480831CrossRefGoogle Scholar
Miau, J.J., Chen, C.R. & Chou, J.H. 1995 A vertically oscillating plate disturbing the development of a boundary layer. J. Fluid Mech. 298, 1–22.10.1017/S0022112095003211CrossRefGoogle Scholar
Miau, J.J., Chen, M.H. & Chou, J.H. 1991 Frequency effect of an oscillating plate immersed in a turbulent boundary layer. AIAA J. 29 (7), 1068–1074.10.2514/3.59954CrossRefGoogle Scholar
Mistry, D., Philip, J. & Dawson, J. 2019 Kinematics of local entrainment and detrainment in a turbulent jet. J. Fluid Mech. 871, 896–924.10.1017/jfm.2019.327CrossRefGoogle Scholar
Mistry, D., Philip, J., Dawson, J.R. & Marusic, I. 2016 Entrainment at multi-scales across the turbulent/non-turbulent interface in an axisymmetric jet. J. Fluid Mech. 802, 690–725.10.1017/jfm.2016.474CrossRefGoogle Scholar
Mohammed-Taifour, A. & Weiss, J. 2016 Unsteadiness in a large turbulent separation bubble. J. Fluid Mech. 799, 383–412.10.1017/jfm.2016.377CrossRefGoogle Scholar
Morlet, J. 1983 Sampling theory and wave propagation. In Issues in Acoustic Signal — Image Processing and Recognition, (ed. C.H. Chen), pp. 233–261. Springer.10.1007/978-3-642-82002-1_12CrossRefGoogle Scholar
Neamtu-Halic, M.M., Krug, D., Mollicone, J., van Reeuwijk, M., Haller, G. & Holzner, M. 2020 Connecting the time evolution of the turbulence interface to coherent structures. J. Fluid Mech. 898, A3.10.1017/jfm.2020.414CrossRefGoogle Scholar
Pan, C., Xue, D., Xu, Y., Wang, J. & Wei, R. 2015 Evaluating the accuracy performance of lucas-kanade algorithm in the circumstance of piv application. Sci. China-Phys. Mech. Astron. 58, 104704.10.1007/s11433-015-5719-yCrossRefGoogle Scholar
Philip, J., Bermejo-Moreno, I., Chung, D. & Marusic, I. 2015 Characteristics of the entrainment velocity in a developing wake. In International Symposium on Turbulence and Shear Flow Phenomena, TSFP-9, vol. 3. Melbourne, Australia.Google Scholar
Qu, Y., Wang, J., Feng, L. & He, X. 2019 Effect of excitation frequency on flow characteristics around a square cylinder with a synthetic jet positioned at front surface. J. Fluid Mech. 880, 764–798.10.1017/jfm.2019.703CrossRefGoogle Scholar
Reuther, N. & Käéhler, C.J. 2020 Effect of the intermittency dynamics on single and multipoint statistics of turbulent boundary layers. J. Fluid Mech. 897, A11.10.1017/jfm.2020.384CrossRefGoogle Scholar
da Silva, C., Hunt, J.C.R., Eames, I. & Westerweel, J. 2014 a Interfacial layers between regions of different turbulence intensity. Annu. Rev. Fluid Mech. 46 (1), 567–590.10.1146/annurev-fluid-010313-141357CrossRefGoogle Scholar
da Silva, C.B., Taveira, R.R. & Borrell, G. 2014 b Characteristics of the turbulent/nonturbulent interface in boundary layers, jets and shear-free turbulence. J. Phys.: Conference Ser. 506 (1), 012015.Google Scholar
da Silva, C.B. & Taveira, R.R. 2010 The thickness of the turbulent/nonturbulent interface is equal to the radius of the large vorticity structures near the edge of the shear layer. Phys. Fluids 22, 121702.10.1063/1.3527548CrossRefGoogle Scholar
Silva, T.S., Zecchetto, M. & da Silva, C.B. 2018 The scaling of the turbulent/non-turbulent interface at high Reynolds numbers. J. Fluid Mech. 843, 156–179.10.1017/jfm.2018.143CrossRefGoogle Scholar
Singh, M., Naughton, J.W., Yamashita, T., Nagai, H. & Asai, K. 2011 Surface pressure and flow field behind an oscillating fence submerged in turbulent boundary layer. Exp. Fluids 50, 701–714.10.1007/s00348-010-0977-yCrossRefGoogle Scholar
Singh, P., Lindberg, W. & Naughton, J. 2005 Flow structures generated by oscillating fences in boundary layer flows. In 35th AIAA Fluid Dynamics Conference and Exhibit, pp. 2005–4882.Google Scholar
Su, S., Long, Y., Wang, J. & Li, X. 2024 Investigations on the turbulent/non-turbulent interface in supersonic compressible plate turbulent boundary layer. J. Fluid Mech. 988, A30.10.1017/jfm.2024.439CrossRefGoogle Scholar
Wang, J.-S. & Wang, J.-J. 2021 Vortex dynamics for flow around the slat cove at low Reynolds numbers. J. Fluid Mech. 919, A27.10.1017/jfm.2021.385CrossRefGoogle Scholar
Watanabe, T., Jaulino, R., Taveira, R.R., da Silva, C.B., Nagata, K. & Sakai, Y. 2017 a Role of an isolated eddy near the turbulent/non-turbulent interface layer. Phys. Rev. Fluids 2, 094607.10.1103/PhysRevFluids.2.094607CrossRefGoogle Scholar
Watanabe, T., Sakai, Y., Nagata, K., Ito, Y. & Hayase, T. 2014 Vortex stretching and compression near the turbulent/non-turbulent interface in a planar jet. J. Fluid Mech. 758, 754–785.10.1017/jfm.2014.559CrossRefGoogle Scholar
Watanabe, T., Sakai, Y., Nagata, K., Ito, Y. & Hayase, T. 2015 Turbulent mixing of passive scalar near turbulent and non-turbulent interface in mixing layers. Phys. Fluids 27 (8), 085109.10.1063/1.4928199CrossRefGoogle Scholar
Watanabe, T., da Silva, C.B., Nagata, K. & Sakai, Y. 2017 b Geometrical aspects of turbulent/non-turbulent interfaces with and without mean shear. Phys. Fluids 29, 085105.10.1063/1.4996199CrossRefGoogle Scholar
Watanabe, T., da Silva, C.B., Sakai, Y., Nagata, K. & Hayase, T. 2016 Lagrangian properties of the entrainment across turbulent/non-turbulent interface layers. Phys. Fluids 28 (3), 031701.10.1063/1.4942959CrossRefGoogle Scholar
Welch, P. 1967 The use of fast fourier transform for the estimation of power spectra: a method based on time averaging over short, modified periodograms. IEEE Trans. Audio Electroacoust. 15 (2), 70–73.10.1109/TAU.1967.1161901CrossRefGoogle Scholar
Westerweel, J., Fukushima, C., Pedersen, J.M. & Hunt, J.C.R. 2009 Momentum and scalar transport at the turbulent/non-turbulent interface of a jet. J. Fluid Mech. 631, 199–230.10.1017/S0022112009006600CrossRefGoogle Scholar
White, F.M. 1991 Viscous Fluid Flow. Mcgraw-Hill, Inc.Google Scholar
Wolf, M., Lüthi, B., Holzner, M., Krug, D., Kinzelbach, W. & Tsinober, A. 2012 Investigations on the local entrainment velocity in a turbulent jet. Phys. Fluids 24 (10), 105110.10.1063/1.4761837CrossRefGoogle Scholar
Woods, J.W. 2011 Multidimensional Signal, Image, and Video Processing and Coding. Academic Press.Google Scholar
Wu, D., Wang, J., Cui, G. & Pan, C. 2020 Effects of surface shapes on properties of turbulent/non-turbulent interface in turbulent boundary layers. Sci. China Technol. Sci. 63, 214–222.10.1007/s11431-018-9434-5CrossRefGoogle Scholar
Wu, X., Wallace, J.M. & Hickey, J.P. 2019 Boundary layer turbulence and freestream turbulence interface, turbulent spot and freestream turbulence interface, laminar boundary layer and freestream turbulence interface. Phys. Fluids 31, 045104.10.1063/1.5093040CrossRefGoogle Scholar
Wu, Y. & Christensen, K.T. 2006 Population trends of spanwise vortices in wall turbulence. J. Fluid Mech. 568, 55–76.10.1017/S002211200600259XCrossRefGoogle Scholar
Xi, Heng-Dong, Peng, Sheng-Hong & Zhang, Yi-Bao 2025 Turbulent/non-turbulent interface in water jet with polymer additives, In Proceedings of the IUTAM Symposium on Turbulent/Non-Turbulent Interface in Turbulent Shear Flows, {ed. Jinjun Wang & Marusic Ivan} pp. 226–237. Cham: Springer 1072 Nature Switzerland.10.1007/978-3-031-78151-3_18CrossRefGoogle Scholar
Xie, Y., Zhang, X., Xiong, X.-L. & Zhou, Y. 2024 Temporal evolution of the turbulence interface of a turbulent plane jet. J. Fluid Mech. 1001, A39.10.1017/jfm.2024.1107CrossRefGoogle Scholar
Xu, C., Long, Y. & Wang, J. 2023 Entrainment mechanism of turbulent synthetic jet flow. J. Fluid Mech. 958, A31.10.1017/jfm.2023.102CrossRefGoogle Scholar
Xu, C. & Wang, J. 2024 Vortex ring breakdown dominating the entrainment of a synthetic jet. J. Fluid Mech. 980, A5.10.1017/jfm.2023.1100CrossRefGoogle Scholar
Zecchetto, M. & da Silva, C.B. 2021 Universality of small-scale motions within the turbulent/non-turbulent interface layer. J. Fluid Mech. 916, A9.10.1017/jfm.2021.168CrossRefGoogle Scholar
Zhang, H., Rival, D.E. & Wu, X. 2021 Kinematics of the turbulent and nonturbulent interfaces in a subsonic airfoil flow. AIAA J. 59, 2155–2168.10.2514/1.J059651CrossRefGoogle Scholar
Zhang, H. & Wu, X. 2022 Dynamics of turbulent and nonturbulent interfaces in cylinder and airfoil near wakes. AIAA J. 60 (1), 261–275.Google Scholar
Zhang, X., Watanabe, T. & Nagata, K. 2023 Reynolds number dependence of the turbulent/non-turbulent interface in temporally developing turbulent boundary layers. J. Fluid Mech. 964, A8.10.1017/jfm.2023.329CrossRefGoogle Scholar
Zhou, J., Adrian, R.J., Balachandar, S. & Kendall, T.M. 1999 Mechanisms for generating coherent packets of hairpin vortices in channel flow. J. Fluid Mech. 387, 353–396.10.1017/S002211209900467XCrossRefGoogle Scholar