2006 Fiscal Year Final Research Report Summary
Rheological Characteristics and Dynamical Mechanism in Hyperconcentrated Sediment-laden Flow
| Project/Area Number |
17560462
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
水工水理学
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| Research Institution | Kumamoto University |
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Principal Investigator |
OHMOTO Terunori Kumamoto Univ., Graduate School of Science and Technology Dep. of Civil and Environmental Eng., Professor., 大学院自然科学研究科, 教授 (30150494)
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| Project Period (FY) |
2005 – 2006
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| Keywords | hypercon centrated sediment / non-Newtonian properties / Yellow River / Rheology / flow resistance / mudflows / gravel bed / dune type bed |
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| Research Abstract |
The need to understand and predict flows that carry large suspended sediment loads has become acute in the Yellow River basin where significant erosion and siltation associated with hyperconcentrated sediment-laden flood give rise to many serious river problems. Mud flows, debris flows or slurries, made up of a large amount of clay and/or silt particles suspended in water, often show non-Newtonian properties but remain poorly understood concerning their rheological properties.
First of all, this paper concerns an experimental study of the fully developed turbulent pipe flow with kaolin particles or silt particles deposited in lower region of the Yellow River Basin. The flow data include friction factor vs. Reynolds number, volumetric sediment concentration, mean flow velocity. In addition, the rheological properties of the mudflows were investigated by using both coaxial cylinder rheometer and parallel plate one. The experimental results stressed that at high sediment concentration mudf
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lows did not fit to the Bingham model at low shear rates, the friction factor increased with the sediment concentration which result from the viscosity increase by two to three orders magnitude.
In addition, we experimentally investigated the effects of non-Newtonian fluid on the separation vortex over fixed dune type bed by using Particle Image Velocimetry(PIV). The results showed that rheological properties significantly dissipated the turbulent flow fluctuations over the dune bed and augmented the flow resistance by comparison with the clear water flow.
Finally, we experimentally investigated the effects of non-Newtonian fluid on resistance characteristics and flow structure over gravel bed by using Particle Image Velocimetry (PIV). The results showed that Kaolin water mixtures in gravel bed open channel flows considerably changed flow structures and took the form of resistance decrease with Kaolin fraction Cv in the region of Cv <8% and followed by a subsequent increase in the region of Cv >8%. Less
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