Type of Document Master's Thesis Author Kanellopoulos, Paul M. URN etd-011999-232112 Title Incipient Motion Under Shallow Flow Conditions Degree Master of Science Department Civil Engineering Advisory Committee
Advisor Name Title Diplas, Panayiotis Committee Chair Dancey, Clinton L. Committee Member Loganathan, G. V. Committee Member Keywords
- Probability of Entrainment
- Rough Walls
- Surface Waves
- Shallow Flows
- Threshold Conditions
- Relative Depth
- Mountain Rivers
Date of Defense 1998-12-16 Availability unrestricted AbstractLaboratory experiments were conducted to investigate the effect of low relative depth
and high Froude number on the dimensionless critical shear stress (Shields parameter).
Spherical particles of four different densities and an 8mm diameter were used as movable test
material. The relative depth ranged from 2 to 12 and the Froude number ranged from 0.36 to 1.29.
The results show that the traditional Shields diagram cannot be used to predict the incipient
motion of coarse sediment particles when the relative depth is below 10 and the Froude number
is above 0.5, approximately. Experiments using glass balls, whose density is almost identical
to that of natural gravel, show that the Shields parameter can be twice as large in shallow flows
than in deep flows. The results also show that the Shields parameter is dependent on the density
of the particles. Data obtained from other studies support the findings of the present work.
These findings can result in significant cost savings for riprap.
Additionally, velocity profiles using a laser-Doppler velocimeter (LDV) were taken for
the glass ball incipient motion experiments. The purpose of this was to study possible changes in
the velocity distribution with decreasing relative depth and increasing Froude number.
The results show that the von Karman and integral constants in the law of the wall do not change
in the range of relative depths and Froude numbers tested.
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