Effects of Bed Forms and Large Protruding Grains on Near‐Bed Flow Hydraulics in Low Relative Submergence Conditions
Tóm tắt
In mountain rivers, bed forms, large relatively immobile grains, and bed texture and topographic variability can significantly alter local and reach‐averaged flow characteristics. The low relative submergence of large immobile grains causes highly three‐dimensional flow fields that may not be represented by traditional shear stress, flow velocity, and turbulence intensity equations. To explore the influence of large protruding grains and bed forms on flow properties, we conducted a set of experiments in which we varied the relative submergence while holding the sediment transport capacity and upstream sediment supply constant. Flow and bed measurements were conducted at the beginning and end of each experiment to account for the absence or presence of bed forms, respectively. Detailed information on the flow was obtained by combining our measurements with a 3‐D numerical model. Commonly used velocity profile equations only performed well at the reach scale when shallow flow effects and the roughness length of the relatively mobile sediment were considered. However, at the local scale large deviations from these profiles were observed and simple methods to estimate the spatial distribution of near‐bed shear stresses are likely to be inaccurate. Zones of high turbulent kinetic energy occurred near the water surface and were largely controlled by the immobile grains and plunging flow. The reach‐averaged shear stress did not correlate to depth or slope, as commonly assumed, but instead was controlled by the relative boulder submergence and degree of plunging flow. For accurate flow predictions in mountain rivers, the effects of bed forms and large boulders must be considered.
Từ khóa
Tài liệu tham khảo
Aghaee Y., 2010, International conference on fluvial hydraulics, river flow 2010, 211
Blanckaert K., 2010, Topographic steering, flow recirculation, velocity redistribution, and bed topography in sharp meander bends, Water Resources Research, 46, W09506
Bohorquez P.(2008).Computational continuum mechanics for sediment transport in free‐surface flow. Open Source CFD International Conference (p. 17). Berlin Germany.
Budwig R. S., 2012, Innovations 2012: World innovations in engineering education and research, 17
Bunte K. &Abt S. R.(2001).Sampling surface and subsurface particle‐size distributions in wadable gravel‐ and cobble‐bed streams for analyses in sediment transport hydraulics and Streambed monitoring(General Tech. Rep. RMRS‐GTR‐74). Fort Collins CO: US Department of Agriculture Forest Service Rocky Mountain Research Station.
Chanson H., 2004, Drag reduction in skimming flow on stepped spillways by aeration, Journal of Hydraulic Research, 42, 316
Clifford N. J., 1993, Turbulence: Perspectives on flow and sediment transport, 93
Cohen J., 2003, Applied multiple regression/correlation analysis for the behavioral sciences
Dietrich W. E., 2005, 4th IAHR symposium on river coastal and estuarine morphodynamics RCEM 2005, 79
Esmaeili T., 2009, 3D Numerical simulation of scouring around bridge piers (case study: Bridge 524 crosses the Tanana River), World Academy of Science, Engineering and Technology, 58, 1028
Francalanci S., 2005, 4th IAHR symposium on river coastal and estuarine morphodynamics RCEM 2005, 13
Frizell K. W., 2002, 2000 joint conference on water resource engineering and water resources planning and management, 1
Grass A. J., 1970, Initial instability of fine sand, Journal of the Hydraulics Division: American Society of Civil Engineers, 96, 619, 10.1061/JYCEAJ.0002369
Griffith J. S., 1999, Inland fisheries management in North America, 405
Grotjans H., 1998, Computational fluid dynamics ‘98, ECCOMAS, 1112
Gupta S. K., 2011, Modern hydrology and sustainable water development
Howell D. C., 2010, Statistical methods for psychology
Jarrett R. D.(1985).Determination of roughness coefficients for streams in Colorado. U.S. Geological Survey Water‐resources investigations report 85–4004 Lakewood CO.
Karagiannis N., 2015, 36th IAHR world congress, 3862
Karagiannis N., 2015, 36th IAHR world congress, 141
Kellerhals R., 1971, Sampling procedures for coarse fluvial sediments, Journal of Hydraulics Division, ASCE, 97, 1165, 10.1061/JYCEAJ.0003044
Kilpatrick F. A., 1989, Techniques of water‐resources investigations of the United States geological survey—applications of hydraulics, 1
Kinerson D.(1990).Surface response to sediment supply (M.Sc. Thesis 108 pp.).Berkeley CA:University of California.
Lepp L. R., 1993, Channel erosion in steep gradient, gravel‐paved streams, Bulletin of the Association of Engineering Geologists, 30, 443
MacMurray H. L.(1985).The use of the salt‐velocity method for the precise measurement of resistance to flow in rough‐boundary open channels (Ph.D. Thesis). Christchurch New Zealand: Department of Environmental Management University of Canterbury.
Menter F. R., 2001, 16th Brazilian congress of mechanical engineering, 117
Menter F. R., 2003, International gas turbine congress 2003, 1
Morgan G. C. J.(2013).Application of the interFoam VOF code to coastal wave/structure interaction (Ph.D. Thesis). Bath UK: Department of Architecture and Civil Engineering University of Bath.
Nelson J. M. &McDonald R. R.(1995).Mechanics and modeling of flow and bed evolution in lateral separation eddies.Flagstaff AZ:US Geological Survey Glen Canyon Environmental Studies Report.
Nezu L., 1993, Turbulence in open channel flows, IAHR Monographs
Papanicolaou A. N., 2005, 4th IAHR symposium on river coastal and estuarine morphodynamics RCEM 2005, 1083
Papanicolaou A., 2010, International conference on fluvial hydraulics, river flow 2010, 793
Rodriguez P.(2008).Study and numerical simulation of sediment transport in free‐surface Flow (Ph.D. Thesis). Malaga Spain: Department of Mechanical Engineering and Fluid Mechanics University of Malaga.
Stoesser T. vonTerzi D. Rodi W. &Olsen N. R. B.(2006).RANS simulation and LES of Flow over dunes at low relative submergence ratios. Paper presented at 7th International Conference on Hydroscience and Engineering Drexel University Philadelphia.
Straub L. G., 1954, Velocity measurement of air‐water mixtures, Transactions of the American Society of Civil Engineers, 119, 207, 10.1061/TACEAT.0007098
Sutcliffe A. G.(2014).Modelling the effects of aquatic plant growth and management on the hydraulics of a chalk stream (Ph.D. thesis 363 pp.). London England: Queen Mary University of London.
Weller H. G.(2005).Derivation modelling and solution of the conditionally averaged two‐phase flow equations(Tech. Rep.).London England:OpenCFD Ltd.
Whittaker J. G., 1986, 9th Australasian Fluid Mechanics Conference, 358
Zanke U. C. E., 2003, On the influence of turbulence on the initiation of sediment motion, International Journal of Sediment Research, 18, 17
Zeng J., 2005, 31st international association hydraulic research congress, 554