4.0 sediemnt transport in channels

Question 1

sieve size corresponding to each soil type

Answer 1

clay <0.004 mm
silt 0.004-0.062
sand 0.062-2 
gravel 2-64 
boulders >64

Question 2

what values of std dv geometric for sieve size represents what

Answer 2

1

Question 3

what are threshold conditions

Answer 3

flow conditions that will initiate sediment motion of boundary conditions

Question 4

what are the two forces on a grain

Answer 4

drag (skin friction, and form )

lift (pressure differences between stagnation pressures and pressures due to flow streamlines

Question 5

what did white considere when it came to threshold conditions for sediment

Answer 5

a particular grain became unstable and moved by rotation,

Threshold conditions thus implied equality between overturning moment and resisting moment

Question 6

what is the angle of repose

Answer 6

when bed titled to angle of repose grain moves at zero shear

Question 7

what is shields diagream

Answer 7

experimental, relates Re to entrainment function

sliding, drag force = resistance force

Question 8

limitations of shileds

Answer 8

only flat beds consideres
threshold conditions established by extrapolating sediment transport rates back to zero
unifrom grain sizes used
fully developed turbulent flows

does not work for R/d less than 5 or steep slopes S>0.01