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Entrainment of sediment particles by very large-scale motions

Published online by Cambridge University Press:  06 February 2020

S. M. Cameron Open the ORCID record for S. M. Cameron [Opens in a new window] ,
V. I. Nikora Open the ORCID record for V. I. Nikora [Opens in a new window]  and
M. J. Witz
S. M. Cameron*
Affiliation:
School of Engineering, University of Aberdeen, AberdeenAB243UE, UK
V. I. Nikora
Affiliation:
School of Engineering, University of Aberdeen, AberdeenAB243UE, UK
M. J. Witz
Affiliation:
School of Engineering, University of Aberdeen, AberdeenAB243UE, UK
*
†Email address for correspondence: [email protected]
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Abstract

Stereoscopic particle image velocimetry (PIV) configured in two orthogonal planes was utilised to capture the flow structure at the instant of entrainment of spherical bed particles in open-channel flow. Experiments were conducted with lightweight target particles amongst a bed of coplanar fixed spheres with diameters of 16 mm. The protrusions of the target particles were set to give an average entrainment rate of $1/60~\text{s}^{-1}$. These protrusions were established from extensive initial experiments which utilised an automated mechanism to place spheres on the bed of the flume and record the time elapsed until they were entrained by the flow. The results showed that at lower flow depth to particle diameter ratios, bed particles are more stable and require larger protrusions to entrain at the same rate as at a larger depth. This effect is consistent with observations of reduced velocity variance and reduced drag force variance for lower flow submergences. The PIV measurements indicated that particle entrainment is associated with very large-scale motions which extend up to 50 flow depths in the streamwise direction. Contributions of smaller scale velocity and pressure spatial fluctuations are suppressed by a spatial averaging effect related to the particle size, and a temporal averaging effect related to the time taken to fully entrain a particle from its resting pocket. These observations are relevant to sediment transport modelling. However, further data are required to clarify the role of particle lift forces and particle shape in the entrainment process.

JFM classification

Geophysical and Geological Flows: Sediment transport
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 888 , 10 April 2020 , A7
Copyright
© The Author(s), 2020. Published by Cambridge University Press

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References

Adrian, R. J. 2007 Hairpin vortex organization in wall turbulence. Phys. Fluids 19 (4), 041301.CrossRefGoogle Scholar
Ali, S. Z. & Dey, S. 2016 Hydrodynamics of sediment threshold. Phys. Fluids 28 (7), 075103.CrossRefGoogle Scholar
Ancey, C., Davison, A. C., Böhm, T., Jodeau, M. & Frey, P. 2008 Entrainment and motion of coarse particles in a shallow water stream down a steep slope. J. Fluid Mech. 595, 83–114.CrossRefGoogle Scholar
Bendat, J. S. & Piersol, A. G. 2000 Random Data Analysis and Measurement Procedures. IOP Publishing.Google Scholar
Cameron, S. M., Nikora, V. I. & Marusic, I. 2019 Drag forces on a bed particle in open-channel flow: effects of pressure spatial fluctuations and very-large-scale motions. J. Fluid Mech. 863, 494–512.CrossRefGoogle Scholar
Cameron, S. M., Nikora, V. I. & Stewart, M. T. 2017 Very-large-scale motions in rough-bed open-channel flow. J. Fluid Mech. 814, 416–429.CrossRefGoogle Scholar
Celik, A. O., Diplas, P. & Dancey, C. L. 2014 Instantaneous pressure measurements on a spherical grain under threshold flow conditions. J. Fluid Mech. 741, 60–97.CrossRefGoogle Scholar
Celik, A. O., Diplas, P., Dancey, C. L. & Valyrakis, M. 2010 Impulse and particle dislodgement under turbulent flow conditions. Phys. Fluids 22 (4), 046601.CrossRefGoogle Scholar
Cinlar, E. 2013 Introduction to Stochastic Processes. Courier Corporation.Google Scholar
Detert, M., Nikora, V. & Jirka, G. H. 2010 Synoptic velocity and pressure fields at the water–sediment interface of streambeds. J. Fluid Mech. 660, 55–86.CrossRefGoogle Scholar
Diplas, P., Dancey, C. L., Celik, A. O., Valyrakis, M., Greer, K. & Akar, T. 2008 The role of impulse on the initiation of particle movement under turbulent flow conditions. Science 322 (5902), 717–720.CrossRefGoogle ScholarPubMed
Dwivedi, A., Melville, B. W., Shamseldin, A. Y. & Guha, T. K. 2010 Drag force on a sediment particle from point velocity measurements: A spectral approach. Water Resour. Res. 46 (10), W10529.CrossRefGoogle Scholar
Dwivedi, A., Melville, B. W., Shamseldin, A. Y. & Guha, T. K. 2011a Flow structures and hydrodynamic force during sediment entrainment. Water Resour. Res. 47 (1), W10509.CrossRefGoogle Scholar
Dwivedi, A. J., Melville, B. W., Shamseldin, A. Y. & Guha, T. K. 2011b Analysis of hydrodynamic lift on a bed sediment particle. J. Geophys. Res.-Earth 116 (F2), F02015.Google Scholar
Einstein, H. A. 1950 The Bed-Load Function for Sediment Transportation in Open Channel Flows. US Department of Agriculture Washington, DC.Google Scholar
Franca, M. J. & Brocchini, M. 2015 Turbulence in rivers. In Rivers – Physical, Fluvial and Environmental Processes, pp. 51–78. Springer.CrossRefGoogle Scholar
Franca, M. J. & Lemmin, U. 2005 Cross-section periodicity of turbulent gravel-bed river flows. In Proceedings of the 4th River, Coastal and Estuarine Morphodynamics: RCEM 2005, vol. 1, pp. 203–210. CRC Press.Google Scholar
Graf, W. H. 1984 Hydraulics of Sediment Transport. Water Resources Publication.Google Scholar
Grinvald, D. I. & Nikora, V. I. 1988 River Turbulence. Hydrometeoizdat.Google Scholar
Hofland, B. & Booij, R. 2004 Measuring the flow structures that initiate stone movement. In River Flow 2004, pp. 821–830. CRC Press.CrossRefGoogle Scholar
Hutchins, N. & Marusic, I. 2007 Evidence of very long meandering features in the logarithmic region of turbulent boundary layers. J. Fluid Mech. 579, 1–28.CrossRefGoogle Scholar
Hwang, Y. & Cossu, C. 2010 Self-sustained process at large scales in turbulent channel flow. Phys. Rev. Lett. 105 (4), 044505.CrossRefGoogle ScholarPubMed
Kim, K. C. & Adrian, R. J. 1999 Very large-scale motion in the outer layer. Phys. Fluids 11 (2), 417–422.CrossRefGoogle Scholar
Maldonado, S. & de Almeida, G. A. M. 2019 Theoretical impulse threshold for particle dislodgement. J. Fluid Mech. 863, 893–903.CrossRefGoogle Scholar
Monty, J. P., Hutchins, N., Ng, H. C. H., Marusic, I. & Chong, M. S. 2009 A comparison of turbulent pipe, channel and boundary layer flows. J. Fluid Mech. 632, 431–442.CrossRefGoogle Scholar
Naudascher, E. & Rockwell, D. 1994 Flow-Induced Vibrations: An Engineering Guide. Dover.Google Scholar
Nelson, J. M., Shreve, R. L., McLean, S. R. & Drake, T. G. 1995 Role of near-bed turbulence structure in bed load transport and bed form mechanics. Water Resour. Res. 31 (8), 2071–2086.CrossRefGoogle Scholar
Nezu, I. 2005 Open-channel flow turbulence and its research prospect in the 21st century. ASCE J. Hydraul. Engng 131 (4), 229–246.CrossRefGoogle Scholar
Nezu, I. & Nakagawa, H. 1993 Turbulence in Open Channel Flows. Balkema.Google Scholar
Nikora, V., Cameron, S., Albayrak, I., Miler, O., Nikora, N., Siniscalchi, F., Stewart, M. & O’Hare, M. 2012 Flow-biota interactions in aquatic systems: scales, mechanisms, and challenges. In Environmental Fluid Mechanics: Memorial Volume in Honour of Prof. Gerhard H. Jirka (ed. Rodi, W. & Uhlmannm, M.), chap. 11, pp. 217–235. CRC Press.Google Scholar
Nikora, V. & Goring, D. 2000 Flow turbulence over fixed and weakly mobile gravel beds. ASCE J. Hydraul. Engng 126 (9), 679–690.CrossRefGoogle Scholar
Perry, A. E., Lim, K. L. & Henbest, S. M. 1987 An experimental study of the turbulence structure in smooth-and rough-wall boundary layers. J. Fluid Mech. 177, 437–466.CrossRefGoogle Scholar
Raudkivi, A. J. 1998 Loose Boundary Hydraulics. CRC Press.Google Scholar
Raupach, M. R., Antonia, R. A. & Rajagopalan, S. 1991 Rough-wall turbulent boundary layers. Appl. Mech. Rev. 44 (1), 1–25.CrossRefGoogle Scholar
Roy, A. G., Buffin-Belanger, T., Lamarre, H. & Kirkbride, A. D. 2004 Size, shape and dynamics of large-scale turbulent flow structures in a gravel-bed river. J. Fluid Mech. 500, 1–27.CrossRefGoogle Scholar
Schmeeckle, M. W. & Nelson, J. M. 2003 Direct numerical simulation of bedload transport using a local, dynamic boundary condition. Sedimentology 50 (2), 279–301.CrossRefGoogle Scholar
Schmeeckle, M. W., Nelson, J. M. & Shreve, R. L. 2007 Forces on stationary particles in near-bed turbulent flows. J. Geophys. Res.-Earth 112 (F2), F02003.Google Scholar
Séchet, P. & Le Guennec, B. 1999 Bursting phenomenon and incipient motion of solid particles in bed-load transport. J. Hydraul Res. 37 (5), 683–696.CrossRefGoogle Scholar
Shields, A.1936 Anwendung der aehnlichkeitsmechanik und der turbulenzforschung auf die geschiebebewegung. PhD thesis, Technical University Berlin.Google Scholar
Smart, G. M. & Habersack, H. M. 2007 Pressure fluctuations and gravel entrainment in rivers. J. Hydraul Res. 45 (5), 661–673.CrossRefGoogle Scholar
Sutherland, A. J. 1967 Proposed mechanism for sediment entrainment by turbulent flows. J. Geophys. Res. 72 (24), 6183–6194.CrossRefGoogle Scholar
Tsinober, A. 2001 An Informal Introduction to Turbulence. Springer Science & Business Media.Google Scholar
Valyrakis, M., Diplas, P., Dancey, C. L., Greer, K. & Celik, A. O. 2010 Role of instantaneous force magnitude and duration on particle entrainment. J. Geophys. Res.-Earth 115 (F2), F02006.Google Scholar
Wu, F. C. & Shih, W. R. 2012 Entrainment of sediment particles by retrograde vortices: Test of hypothesis using near-particle observations. J. Geophys. Res.-Earth 117 (F3), F03018.Google Scholar
Zaitsev, N. I. 1984 Large-scale eddy structure of turbulent flow in a straight channel. In Proceedings of the State Hydrological Institute, St Petersburg, Russia, vol. 318, pp. 3–17.Google Scholar