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Experimental observations on turbulent boundary layers subjected to a step change in surface roughness

Published online by Cambridge University Press:  16 August 2022

M. Gul Open the ORCID record for M. Gul [Opens in a new window]  and
B. Ganapathisubramani Open the ORCID record for B. Ganapathisubramani [Opens in a new window]
M. Gul*
Affiliation:
Department of Mechanical Engineering, The University of Sheffield, S1 3JD Sheffield, UK
B. Ganapathisubramani
Affiliation:
Engineering and Physical Sciences, University of Southampton, Southampton SO17 1BJ, UK
*
†Email address for correspondence: [email protected]
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Abstract

Based on experimental data acquired with particle image velocimetry, we examine turbulent boundary layers that are subjected to an abrupt change in wall roughness in the streamwise direction. Three different sandpapers (P24, P36 and P60) together with a smooth wall are used to form a number of different surface transition cases, including both R $\rightarrow$ S (where upstream surface is rough and second surface is either smooth or smoother compared with the upstream surface) and S $\rightarrow$ R (where upstream surface is smoother compared with the downstream surface; both surfaces are rough). This enables us to investigate the effect of the surface transition strength ($M = \ln [y_{02}/y_{01}]$, where $y_{01}$ and $y_{02}$ are the roughness lengths of the upstream and downstream surfaces, respectively) on the growth of the internal boundary layer (IBL) and the corresponding flow structure. The results show that for each surface transition group (i.e. R $\rightarrow$ S and S $\rightarrow$ R), the thickness of the IBLs is proportional to the strength of the surface transition, and that the IBLs are thicker for the S $\rightarrow$ R cases compared with their R $\rightarrow$ S counterparts for similar $|M|$, when normalised by the initial boundary layer thickness ($\delta _0$). The results also show that the growth rates of the IBLs could be represented by a power law, consistent with the previous studies. However, despite a wide range of scatter in the literature for the power-law exponent, an average value of $0.75$ (varies between $0.71$ and $0.8$ with no clear trend) is obtained in the present study considering all the surface transition cases. The pre-factor for the power-law fit, on the other hand, is found to be related to the strength of the surface transition. In addition to the variations in the velocity defect and diagnostic plots with the growth of the IBLs, sweep and ejection events appear to differ significantly (depending on the type of the step change). Two-point spatial correlations, moreover, show that the structure is more elongated in the wall-normal and streamwise directions, as the flow accelerates over the downstream surface (i.e. R $\rightarrow$ S cases). For the reverse transition cases (i.e. S $\rightarrow$ R, where the flow decelerates over the downstream rougher surface), however, the correlation coefficients shrink in size in both directions.

JFM classification

Turbulent Flows: Turbulent boundary layers
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 947 , 25 September 2022 , A6
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Copyright
© The Author(s), 2022. Published by Cambridge University Press

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References

REFERENCES

Alfredsson, P.H., Orlu, R. & Segalini, A. 2012 A new formulation for the streamwise turbulence intensity distribution in wall-bounded turbulent flows. Eur. J. Mech. B/Fluids 36, 167–175.CrossRefGoogle Scholar
Andreopoulos, J. & Wood, D.H. 1982 The response of a turbulent boundary layer to a short length of surface roughness. J. Fluid Mech. 118, 143–164.CrossRefGoogle Scholar
Antonia, R.A. & Luxton, R.E. 1971 a The response of a turbulent boundary layer to a step change in surface roughness. Part 1. Smooth to rough. J. Fluid Mech. 48, 721–761.CrossRefGoogle Scholar
Antonia, R.A. & Luxton, R.E. 1971 b The response of a turbulent boundary layer to a step change in surface roughness. Part 2. Rough-to-smooth. J. Fluid Mech. 53, 737–757.CrossRefGoogle Scholar
Bou-Zeid, E., Meneveau, C. & Parlange, M.B. 2004 Large-eddy simulation of neutral atmospheric boundary layer flow over heterogeneous surfaces: blending height and effective surface roughness. Water Resour. Res. 40, W02505.CrossRefGoogle Scholar
Bradley, E.F. 1968 A micrometeorological study of velocity profiles and surface drag in the region modified by a change in surface roughness. Q. J. R. Meteorol. Soc. 94, 361–379.CrossRefGoogle Scholar
van Buren, T., Floryan, D., Ding, L., Hellström, L.H.O. & Smits, A.J. 2020 Turbulent pipe flow response to a step change in surface roughness. J. Fluid Mech. 904, A38.CrossRefGoogle Scholar
Castro, I.P. 2007 Rough-wall boundary layers: mean flow universality. J. Fluid Mech. 585, 469–485.CrossRefGoogle Scholar
Chamorro, L.P. & Porte-Agél, F. 2009 Velocity and surface shear stress distributions behind a rough-to-smooth surface transition: a simple new model. Boundary-Layer Meteorol. 130, 29–41.CrossRefGoogle Scholar
Efros, V. & Krogstad, P. 2011 Development of a turbulent boundary layer after a step from smooth to rough surface. Exp. Fluids 51, 1563–1575.CrossRefGoogle Scholar
Elliott, W.P. 1958 The growth of the atmospheric internal boundary layer. Trans. Am. Geophys. Union 39, 1048–1054.CrossRefGoogle Scholar
Ghaisas, N.S. 2020 A predictive analytical model for surface shear stresses and velocity profiles behind a surface roughness jump. Boundary-Layer Meteorol. 176, 49–368.CrossRefGoogle Scholar
Gul, M. & Ganapathisubramani, B. 2021 Revisiting rough-wall turbulent boundary layers over sand-grain roughness. J. Fluid Mech. 911, A26.CrossRefGoogle Scholar
Hanson, R.E. & Ganapathisubramani, B. 2016 Development of turbulent boundary layers past a step change in wall roughness. J. Fluid Mech. 795, 494–523.CrossRefGoogle Scholar
Hutchins, N., Monty, J.P., Ganapathisubramani, B., Ng, H.C.H. & Marusic, I. 2011 Three-dimensional conditional structure of a high-Reynolds-number turbulent boundary layer. J. Fluid Mech. 673, 255–285.CrossRefGoogle Scholar
Ismail, U., Zaki, T.A. & Durbin, P.A. 2018 Simulations of rib-roughened rough-to-smooth turbulent channel flows. J. Fluid Mech. 843, 419–449.CrossRefGoogle Scholar
Lee, J.H. 2015 Turbulent boundary layer flow with a step change from smooth to rough surface. Intl J. Heat Fluid Flow 54, 39–54.CrossRefGoogle Scholar
Li, M. 2020 Towards modelling the downstream development of a turbulent boundary layer following a rough-to-smooth step change. PhD thesis, University of Melbourne.Google Scholar
Li, M., de Silva, C.M., Chung, D., Pullin, D.I., Marusic, I. & Hutchins, N. 2021 Experimental study of a turbulent boundary layer with a rough-to-smooth change in surface conditions at high Reynolds numbers. J. Fluid Mech. 923, A18.CrossRefGoogle Scholar
Li, M., de Silva, C.M., Rouhi, A., Baidya, R., Chung, D., Marusic, I. & Hutchins, N. 2019 Recovery of wall-shear stress to equilibrium flow conditions after a rough-to-smooth step change in turbulent boundary layers. J. Fluid Mech. 872, 472–491.CrossRefGoogle Scholar
Li, W. & Liu, C.H. 2022 On the flow response to an abrupt change in surface roughness. Flow Turbul. Combust. 108, 387–409.CrossRefGoogle Scholar
Lu, S.S. & Willmarth, W.W. 1973 Measurements of the structure of the Reynolds stress in a turbulent boundary layer. J. Fluid Mech. 60, 481–511.CrossRefGoogle Scholar
Mulhearn, P.J. 1978 A wind-tunnel boundary-layer study of the effects of a surface roughness change: rough to smooth. Boundary-Layer Meteorol. 15, 13–30.CrossRefGoogle Scholar
Nikuradse, J. 1950 Laws of flow in rough pipes. NACA Tech. Mem. NACA TM-1292.Google Scholar
Panofsky, H.A. 1973 Tower micrometeorology. In Workshop on Micrometeorology (ed. D.A. Haugen), pp. 151–176. American Meteorological Society.Google Scholar
Panofsky, H.A. & Dutton, J.A. 1984 Atmospheric Turbulence. Wiley (Interscience).Google Scholar
Panofsky, H.A. & Townsend, A.A. 1964 Change of terrain roughness and the wind profile. Q. J. R. Meteorol. Soc. 90, 147–155.CrossRefGoogle Scholar
Pendergrass, W. & Aria, S.P.S. 1984 Dispersion in neutral boundary layer over a step change in surface roughness – I. Mean flow and turbulence structure. Boundary-Layer Meteorol. 18, 1267–1279.Google Scholar
Rouhi, A., Chung, D. & Hutchins, N. 2019 Direct numerical simulation of open-channel flow over smooth-to-rough and rough-to-smooth step changes. J. Fluid Mech. 866, 450–486.CrossRefGoogle Scholar
Saito, N & Pullin, D.I. 2014 Large eddy simulation of smooth–rough–smooth transitions in turbulent channel flows. Intl J. Heat Mass Transfer 78, 707–720.CrossRefGoogle Scholar
Savelyev, S.A. & Taylor, P.A. 2001 Notes on internal boundary-layer height formula. Boundary-Layer Meteorol. 101, 293–301.CrossRefGoogle Scholar
Schultz, M.P., Bendick, J.A., Holm, E.R. & Hertel, W.M. 2011 Economic impact of biofouling on a naval surface ship. Biofouling 27, 87–98.CrossRefGoogle ScholarPubMed
Spalart, P.R. & McLean, J.D. 2011 Drag reduction: enticing turbulence, and then an industry. Phil. Trans. R. Soc. A 369, 1556–1569.CrossRefGoogle ScholarPubMed
Townsend, A.A. 1956 The structure of turbulent shear flow, vol. 1. Cambridge University Press.Google Scholar
Townsend, A.A. 1965 The responce of a turbulent boundary layer to abrupt changes in surface conditions. J. Fluid Mech. 22, 799–822.CrossRefGoogle Scholar
Wood, D.H. 1982 Internal boundary-layer growth following a change in surface roughness. Boundary-Layer Meteorol. 22, 241–244.CrossRefGoogle Scholar