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Instantaneous pressure measurements on a spherical grain under threshold flow conditions

  • Ahmet O. Celik (a1), P. Diplas (a2) and C. L. Dancey (a3)

Abstract

The aim of this investigation was to experimentally examine the surface pressures and resulting forces on an individual sediment grain whose size is comparable to the scales of the turbulent channel flow in an effort to discern details of the flow/grain interaction. This was accomplished by measuring the pressure fluctuations on the surface of a coarse, fully exposed, spherical grain resting upon a bed of identical grains in open channel turbulent flow. This spherical particle was instrumented with low-range, high-frequency-response pressure transducers to measure the individual surface pressures simultaneously on its front, back, top and bottom. The local flow velocity was measured synchronously with a laser Doppler velocimeter. The flow and sediment are near threshold conditions for entrainment with the channel and particle Reynolds numbers varying between 31 000–39 000 and 330–440 respectively. The emphasis was on determining the characteristics of the flow field with the potential to dislodge a spherical grain under uniform flow conditions as well as in the wake of a circular cylinder placed spanwise across the flow in otherwise fully developed open channel flow. It is concluded that the streamwise velocity near the bed is most directly related to those force events (and associated individual surface pressure distributions) crucial for particle entrainment. The lift force was observed to momentarily reach values which can be consequential for particle stability, although it is poorly correlated with the fluctuating normal velocity component. Turbulence intensity near the bed, rather than being the causative factor for increased force fluctuations, was shown to be an indicator of changes in the average lift force experienced by the grain during the application of extreme drag forces, at least for this particular flow condition (the upstream, spanwise-mounted circular cylinder). This effect is known to alter the sediment transport rates significantly. The characteristics of the temporal durations of flow events about the local maxima in the stagnation pressure, drag and lift forces, using a conditional sampling method, revealed the prevalence of sweep-type near-bed flow events in generating favourable conditions for particle dislodgement, although the dominant feature is the positive streamwise velocity fluctuation, not the normal velocity component. The duration of such events was the highest in the fourth and first quadrants in the $u,w$ plane, inducing high impulses on the grain.

Copyright

Corresponding author

Email address for correspondence: aocelik@anadolu.edu.tr

References

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Ancey, C., Bohm, T., Jodeau, M. & Frey, P. 2006 Statistical description of sediment transport experiments. Phys. Rev. E 74 (1), 114.
Balakrishnan, M.1997 The role of turbulence on the entrainment of a single sphere and the effects of roughness on fluid-solid interaction. PhD thesis, Virginia Polytechnic Institute and State University.
Brayshaw, A. C., Frostick, L. E. & Reid, I. 1983 The hydrodynamics of particle clusters and sediment entrapment in coarse alluvial channels. Sedimentology 30 (1), 137143.
Bushnell, D. M. & McGinley, C. B. 1989 Turbulence control in wall flows. Annu. Rev. Fluid Mech. 21, 120.
Cameron, S. M.2006 Near-boundary flow structure and particle entrainment. PhD thesis, University of Auckland.
Celik, A. O.2011 Experimental investigation of the role of turbulence fluctuations on incipient motion of sediment. PhD thesis, Virginia Polytechnic Institute and State University.
Celik, A. O., Diplas, P., Dancey, C. L. & Valyrakis, M. 2010 Impulse and particle dislodgement under turbulent flow conditions. Phys. Fluids 22, 046601.
Cheng, N. S., Law, A. W. K. & Lim, S. Y. 2003 Probability distribution of bed particle instability. Adv. Water Resour. 26 (4), 427433.
Derksen, J. J. & Larsen, R. A. 2011 Drag and lift forces on random assemblies of wall-attached spheres in low-Reynolds number shear flow. J. Fluid Mech. 673, 548573.
Detert, M., Nikora, V. & Jirka, G. H. 2010a Synoptic velocity and pressure fields at the water-sediment interface of streambeds. J. Fluid Mech. 660, 5586.
Detert, M., Weitbrecht, V. & Jirka, G. H. 2010b Laboratory measurements on turbulent pressure fluctuations in and above gravel beds. J. Hydraul. Engng 136, 779789.
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, 717720.
Dwivedi, A., Melville, B. & Shamseldin, A. Y. 2010a Hydrodynamic forces generated on a spherical sediment particle during entrainment. J. Hydraul. Engng 136 (10), 756769.
Dwivedi, A., Melville, B., Shamseldin, A. Y. & Guha, T. K. 2010b Drag force on a sediment particle from point velocity measurements: a spectral approach. Water Resour. Res. 46, W10529.
Dwivedi, A., Melville, B., Shamseldin, A. Y. & Guha, T. K. 2011 Flow structures and hydrodynamic force during sediment entrainment. Water Resour. Res. 47, W01509.
Einstein, H. A. & El-Samni, E. A. 1949 Hydrodynamic forces on a rough wall. Rev. Mod. Phys. 21 (3), 520524.
Heathershaw, A. D. & Thorne, P. D. 1985 Sea-bed noises reveal role of turbulent bursting phenomenon in sediment transport by tidal currents. Nature 316, 339342.
Hofland, B.2005 Rock and roll turbulence-induced damage to granular bed protections. PhD thesis, TU Delft, www.library.tudelft.nl.
Hofland, B. & Battjes, J. 2006 Probability density function of instantaneous drag forces and shear stresses on a bed. J. Hydraul. Engng 132, 11691175.
Hofland, B., Booij, R. & Battjes, J. 2005 Measurement of fluctuating pressures on coarse bed material. J. Hydraul. Engng 131 (9), 770781.
Jackson, R. G. 1976 Sedimentological and fluid-dynamic implications of the turbulent bursting phenomenon in geophysical flows. J. Fluid Mech. 77, 531560.
Johansson, A. V., Her, J. Y. & Haritonidis, J. H. 1987 On the generation of high-amplitude wall-pressure peaks in turbulent boundary layers and spots. J. Fluid Mech. 175, 119142.
Kalinske, A. A. 1947 Movement of sediment as bed load in rivers. Trans. AGU 28 (4), 615620.
Keshavarzi, A. R. & Gheisi, A. R. 2006 Stochastic nature of three-dimensional bursting events and sediment entrainment in vortex chamber. Stoch. Env. Res. Risk A. 21 (1), 7587.
Kirchner, J. W., Dietrich, W. E., Iseya, F. & Ikeda, H. 1990 The variability of critical shear stress, friction angle, and grain protrusion in water-worked sediments. Sedimentology 37, 647672.
Laadhari, F., Morel, R. & Alcaraz, E. 1994 Combined visualisation and measurements in transitional boundary layers. Eur. J. Mech. (B-Fluids) 13 (4), 473489.
Ling, C. H. 1995 Criteria for incipient motion of spherical sediment particles. J. Hydraul. Engng 121 (6), 472478.
Nelson, J. M., Shreve, R. L., MacLean, 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), 20712086.
Nezu, I. & Nakagawa, H. 1993 In Turbulence in Open Channel Flows IAHR Monograph, Balkema.
Paiement-Paradis, G., Marquis, G. & Roy, A. 2010 Effects of turbulence on the transport of individual particles as bedload in a gravel-bed river. Earth Surf. Process. Landf. 36, 107116.
Paintal, A. S. 1971 Concept of critical shear stress in loose boundary open channels. J. Hydraul. Engng Div. ASCE 9, 91114.
Papanicolaou, A. N., Diplas, P., Evaggelopoulos, N. & Fotopoulos, S. 2002 Stochastic incipient motion criterion for spheres under various bed packing conditions. J. Hydraul. Engng 128 (4), 369380.
van Radecke, H. & Schulz-DuBois, E. O. 1988 Linear response of fluctuating forces to turbulent velocity components. In Fourth International Symposium on Applications of Laser-Doppler Anemometry to Fluid Mechanics (ed. Adrian, R. J.), pp. 2344. Springer.
Radspinner, R., Diplas, P., Lightbody, A. & Sotiropoulos, F. 2010 River training and ecological enhancement using in-stream structures. J. Hydraul. Engng 136 (12), 967980.
Robinson, S. K. 1991 Coherent motions in the turbulent boundary layer. Annu. Rev. Fluid Mech. 22, 631639.
Schmeeckle, M. W. & Nelson, J. M. 2003 Direct numerical simulation of bedload transport using a local dynamic boundary condition. Sedimentology 50, 279301.
Schmeeckle, M. W., Nelson, J. M. & Shreve, R. L. 2007 Forces on stationary particles in near-bed turbulent flows. J. Geophys. Res. 112, 279301.
Shvidchenko, A. B. & Pender, G. 2001 Macroturbulent structure of open-channel flow over gravel beds. Water Resour. Res. 37 (3), 709719.
Smart, G. M. & Habersack, H. M. 2007 Pressure fluctuations and gravel entrainment in rivers. J. Hydraul. Res. 45 (5), 661673.
Song, T., Graf, W. H. & Lemmin, U. 1994 Uniform flow in open channels with movable gravel bed. J. Hydraul. Res. 32 (2), 861876.
Stoesser, T., Frohlich, J. & Rodi, W. 2007 Turbulent open-channel flow over a permeable bed. In Proceedings of 32nd IAHR Congress, Venice, Italy .
Sumer, B. M., Chua, L. H. C., Cheng, N. S. & Fredsoe, J. 2003 Uniform flow in open channels with movable gravel bed. J. Hydraul. Res. 32 (2), 861876.
Sumer, B. M. & Fredsoe, E. J. 2006 Hydrodynamics Around Cylindrical Structures. World Scientific.
Sutherland, A. J. 1967 Proposed mechanism for sediment entrainment by turbulent flows. J. Geophys. Res. 72 (24), 61836194.
Valyrakis, M., Diplas, P., Dancey, C. L., Greer, K. & Celik, A. O. 2010 The role of instantaneous force magnitude and duration on particle entrainment. J. Geophys. Res. 115 (F02006).
Vollmer, S. & Kleinhans, M. G. 2007 Predicting incipient motion, including the effect of turbulent pressure fluctuations in the bed. Water Resour. Res. 43 (W05410).
Williamson, C. H. K. 1996 Vortex dynamics in the cylinder wake. Annu. Rev. Fluid Mech. 28, 477539.
Yoshida, A., Tamura, Y. & Kurita, T. 2001 Effects of bends in a tubing system for pressure measurement. J. Wind Engng Ind. Aerodyn. 89 (20), 17011716.
Zeng, L., Balachandar, S., Fischer, P. & Najjar, F. 2008 Interactions of a stationary finite-sized particle with wall turbulence. J. Fluid Mech. 594, 271305.
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